usage/spec/

cmd.rs

use std::collections::HashMap;
use std::sync::OnceLock;

use crate::error::UsageErr;
use crate::kdl::{KdlDocument, KdlEntry, KdlNode};
use crate::sh::sh;
use crate::spec::builder::SpecCommandBuilder;
use crate::spec::clause::SpecClause;
use crate::spec::context::ParsingContext;
use crate::spec::effect::{SpecCommandEffect, EFFECT_VALUES};
use crate::spec::exit_code::SpecExitCode;
use crate::spec::flagset::SpecUse;
use crate::spec::group::SpecGroup;
use crate::spec::helpers::{string_entry, NodeHelper};
use crate::spec::is_false;
use crate::spec::mount::SpecMount;
use crate::spec::output::SpecOutput;
use crate::spec::unknown_flags::UnknownFlags;
use crate::{Spec, SpecArg, SpecComplete, SpecFlag};
use indexmap::IndexMap;
use itertools::Itertools;
use serde::Serialize;

/// A CLI command or subcommand specification.
///
/// Commands define the structure of a CLI, including their flags, arguments,
/// and nested subcommands. The root command represents the main CLI entry point.
///
/// # Example
///
/// ```
/// use usage::{SpecCommand, SpecFlag, SpecArg};
///
/// let cmd = SpecCommand::builder()
///     .name("install")
///     .help("Install a package")
///     .alias("i")
///     .flag(SpecFlag::builder().short('f').long("force").build())
///     .arg(SpecArg::builder().name("package").required(true).build())
///     .build();
/// ```
#[derive(Debug, Serialize, Clone)]
pub struct SpecCommand {
    /// Full command path from root (e.g., ["git", "remote", "add"])
    pub full_cmd: Vec<String>,
    /// Generated usage string
    pub usage: String,
    /// Nested subcommands indexed by name
    pub subcommands: IndexMap<String, SpecCommand>,
    /// Positional arguments for this command
    pub args: Vec<SpecArg>,
    /// A repeatable separator-delimited positional group.
    #[serde(skip_serializing_if = "Option::is_none")]
    pub clause: Option<SpecClause>,
    /// Flags/options for this command
    pub flags: Vec<SpecFlag>,
    /// Flagsets this command pulls in, and where in [`Self::flags`] they belong.
    ///
    /// `pub(crate)` because it is always empty by the time anyone else can see it: a `use` is
    /// resolved while the spec is read, so a consumer holding a `SpecCommand` holds the flags
    /// the sets named. Visible to the rest of the crate only so that other modules can
    /// destructure `SpecCommand` exhaustively.
    #[serde(skip)]
    pub(crate) uses: Vec<SpecUse>,
    /// Mounted external specs
    pub mounts: Vec<SpecMount>,
    /// Sets of flags that relate to one another as a set.
    ///
    /// Pairwise [`conflicts`](SpecFlag::conflicts) can say everything a plain group says
    /// and cannot say `required`: "one of these is needed" is a statement about the set.
    #[serde(skip_serializing_if = "Vec::is_empty")]
    pub groups: Vec<SpecGroup>,
    /// Deprecation message if this command is deprecated
    #[serde(skip_serializing_if = "Option::is_none")]
    pub deprecated: Option<String>,
    /// Version at which consumers should begin warning about this command.
    #[serde(skip_serializing_if = "Option::is_none")]
    pub deprecated_warn_at: Option<String>,
    /// Version at which consumers expect this command to be removed.
    #[serde(skip_serializing_if = "Option::is_none")]
    pub deprecated_remove_at: Option<String>,
    /// What running this command does to the world: read, write or destructive.
    /// Not inherited by subcommands.
    #[serde(skip_serializing_if = "Option::is_none")]
    pub effect: Option<SpecCommandEffect>,
    /// What to do here with a flag-like token that names no declared flag.
    ///
    /// Unset means "whatever encloses this command decided" — the nearest command
    /// above that set one, or failing that the spec, or failing that
    /// [`UnknownFlags::Value`]. Unlike [`SpecCommandEffect`] this *is* inherited,
    /// because it describes how a command line is read rather than what a command
    /// does, and a CLI that forwards options generally forwards them everywhere.
    pub unknown_flags: Option<UnknownFlags>,
    /// Whether to hide this command from help output
    pub hide: bool,
    /// Help section this command appears under in its parent's command list.
    #[serde(skip_serializing_if = "Option::is_none")]
    pub help_heading: Option<String>,
    /// Named audience or contract surface this command belongs to. Metadata only.
    #[serde(skip_serializing_if = "Option::is_none")]
    pub surface: Option<String>,
    /// Descriptive conditions under which this command is available.
    #[serde(skip_serializing_if = "Vec::is_empty")]
    pub available_if: Vec<String>,
    /// Explicit placement within its parent's command section.
    #[serde(skip_serializing_if = "Option::is_none")]
    pub display_order: Option<usize>,
    /// True when this command came from a [`SpecMount`], i.e. it describes another
    /// program's CLI that was merged in at parse time.
    ///
    /// The flags of the commands *above* a mounted command belong to the mounting CLI,
    /// not to the mounted program, so they are not offered in completions once a mounted
    /// command has been reached. They stay recognized by the parser, since they may
    /// legitimately appear *before* the mounted command on the command line.
    ///
    /// Runtime-only: it is derived from `mount` nodes and is not part of the spec syntax.
    #[serde(skip)]
    pub mounted: bool,
    /// True when a [`SpecMount`] brought flags of its own onto this command. A mounted spec's
    /// root flags are merged into the command the mount sits on, *replacing* that command's
    /// flags (see [`SpecCommand::merge`]), so when this is set every flag here describes the
    /// mounted program and is offered inside the mounted commands accordingly.
    ///
    /// Runtime-only, like [`SpecCommand::mounted`].
    #[serde(skip)]
    pub flags_from_mount: bool,
    /// Whether a subcommand must be provided
    #[serde(skip_serializing_if = "is_false")]
    pub subcommand_required: bool,
    /// Heading used for this command's subcommand section.
    #[serde(skip_serializing_if = "Option::is_none")]
    pub subcommand_help_heading: Option<String>,
    /// Placeholder used for subcommands in the synopsis.
    #[serde(skip_serializing_if = "Option::is_none")]
    pub subcommand_value_name: Option<String>,
    /// Put each argument, flag, and subcommand description on the following line.
    #[serde(skip_serializing_if = "is_false")]
    pub next_line_help: bool,
    /// Expand each visible subcommand's summary and arguments into this command's help page.
    #[serde(skip_serializing_if = "is_false")]
    pub flatten_help: bool,
    /// Fixed help width. Zero disables wrapping.
    #[serde(skip_serializing_if = "Option::is_none")]
    pub term_width: Option<usize>,
    /// Maximum detected terminal width when `term_width` is unset. Zero disables the cap.
    #[serde(skip_serializing_if = "Option::is_none")]
    pub max_term_width: Option<usize>,
    /// Whether an unmatched word is forwarded as an external command plus the rest of argv.
    ///
    /// clap's `allow_external_subcommands` / `#[command(external_subcommand)]`. Known
    /// subcommands still win; a `default_subcommand` still catches first. Once the
    /// unmatched word is taken, remaining tokens — including `--help` — are not parsed
    /// as this command's flags.
    #[serde(skip_serializing_if = "is_false")]
    pub external_subcommand: bool,
    /// Whether a bare invocation of this command shows its help.
    #[serde(skip_serializing_if = "is_false")]
    pub arg_required_else_help: bool,
    #[serde(skip_serializing_if = "is_false")]
    pub disable_help_flag: bool,
    #[serde(skip_serializing_if = "is_false")]
    pub disable_help_subcommand: bool,
    #[serde(skip_serializing_if = "is_false")]
    pub disable_version_flag: bool,
    /// Whether delimiter splitting is disabled after `--` or for an automatic trailing arg.
    #[serde(skip_serializing_if = "is_false")]
    pub dont_delimit_trailing_values: bool,
    /// Whether a later occurrence of a single-valued argument replaces the earlier one.
    /// Permissive by default; set false to report duplicates.
    pub args_override_self: bool,
    /// Whether selecting a subcommand satisfies this command's required arguments.
    #[serde(skip_serializing_if = "is_false")]
    pub subcommand_negates_reqs: bool,
    /// Whether binding an argument prevents selecting a later subcommand.
    #[serde(skip_serializing_if = "is_false")]
    pub args_conflicts_with_subcommands: bool,
    #[serde(skip_serializing_if = "is_false")]
    pub subcommand_precedence_over_arg: bool,
    /// Allow required positionals after optional positionals to claim the remaining words.
    #[serde(skip_serializing_if = "is_false")]
    pub allow_missing_positional: bool,
    /// Token that resets argument parsing, allowing multiple command invocations.
    /// e.g., `mise run lint ::: test ::: check` with restart_token=":::"
    #[serde(skip_serializing_if = "Option::is_none")]
    pub restart_token: Option<String>,
    /// Short help text shown in command listings
    #[serde(skip_serializing_if = "Option::is_none")]
    pub help: Option<String>,
    /// Extended help text shown with --help
    #[serde(skip_serializing_if = "Option::is_none")]
    pub help_long: Option<String>,
    /// Markdown-formatted help text
    #[serde(skip_serializing_if = "Option::is_none")]
    pub help_md: Option<String>,
    /// Command name (e.g., "install")
    pub name: String,
    /// Alternative names for this command
    pub aliases: Vec<String>,
    /// Hidden alternative names (not shown in help)
    pub hidden_aliases: Vec<String>,
    /// Text displayed before the help content
    #[serde(skip_serializing_if = "Option::is_none")]
    pub before_help: Option<String>,
    /// Extended text displayed before help content
    #[serde(skip_serializing_if = "Option::is_none")]
    pub before_help_long: Option<String>,
    /// Markdown text displayed before help content
    #[serde(skip_serializing_if = "Option::is_none")]
    pub before_help_md: Option<String>,
    /// Text displayed after the help content
    #[serde(skip_serializing_if = "Option::is_none")]
    pub after_help: Option<String>,
    /// Extended text displayed after help content
    #[serde(skip_serializing_if = "Option::is_none")]
    pub after_help_long: Option<String>,
    /// Markdown text displayed after help content
    #[serde(skip_serializing_if = "Option::is_none")]
    pub after_help_md: Option<String>,
    /// Usage examples for this command
    pub examples: Vec<SpecExample>,
    /// Prose introducing this command's help sections, by heading title.
    pub headings: Vec<SpecHeading>,
    /// What this command writes, and how a consumer should read it.
    ///
    /// Folded with the spec's CLI-wide outputs on read rather than here — see
    /// [`effective_outputs`](crate::spec::output::effective_outputs).
    #[serde(skip_serializing_if = "Vec::is_empty")]
    pub outputs: Vec<SpecOutput>,
    /// The flag whose *value* picks among [`Self::outputs`], e.g. `--format`.
    ///
    /// The other spelling — a boolean flag picking one output — lives on the output
    /// itself, because that is where it is scoped.
    #[serde(skip_serializing_if = "Option::is_none")]
    pub select: Option<String>,
    /// What this command's exit statuses mean.
    #[serde(skip_serializing_if = "Vec::is_empty")]
    pub exit_codes: Vec<SpecExitCode>,
    /// Custom completers for arguments
    #[serde(skip_serializing_if = "IndexMap::is_empty")]
    pub complete: IndexMap<String, SpecComplete>,

    /// Cache for subcommand name lookups (including aliases).
    ///
    /// `pub(crate)` only so that other modules can destructure `SpecCommand`
    /// exhaustively; it stays private to the crate.
    #[serde(skip)]
    pub(crate) subcommand_lookup: OnceLock<HashMap<String, String>>,
}

impl Default for SpecCommand {
    fn default() -> Self {
        Self {
            full_cmd: vec![],
            usage: "".to_string(),
            subcommands: IndexMap::new(),
            args: vec![],
            flags: vec![],
            uses: vec![],
            mounts: vec![],
            groups: vec![],
            deprecated: None,
            deprecated_warn_at: None,
            deprecated_remove_at: None,
            effect: None,
            unknown_flags: None,
            hide: false,
            help_heading: None,
            surface: None,
            available_if: vec![],
            display_order: None,
            mounted: false,
            flags_from_mount: false,
            subcommand_required: false,
            subcommand_help_heading: None,
            subcommand_value_name: None,
            next_line_help: false,
            flatten_help: false,
            term_width: None,
            max_term_width: None,
            external_subcommand: false,
            arg_required_else_help: false,
            disable_help_flag: false,
            disable_help_subcommand: false,
            disable_version_flag: false,
            dont_delimit_trailing_values: false,
            args_override_self: true,
            subcommand_negates_reqs: false,
            args_conflicts_with_subcommands: false,
            subcommand_precedence_over_arg: false,
            allow_missing_positional: false,
            restart_token: None,
            clause: None,
            help: None,
            help_long: None,
            help_md: None,
            name: "".to_string(),
            aliases: vec![],
            hidden_aliases: vec![],
            before_help: None,
            before_help_long: None,
            before_help_md: None,
            after_help: None,
            after_help_long: None,
            after_help_md: None,
            examples: vec![],
            headings: vec![],
            outputs: vec![],
            select: None,
            exit_codes: vec![],
            subcommand_lookup: OnceLock::new(),
            complete: IndexMap::new(),
        }
    }
}

#[derive(Debug, Default, Serialize, Clone)]
#[non_exhaustive]
pub struct SpecExample {
    pub code: String,
    pub header: Option<String>,
    pub help: Option<String>,
    pub lang: String,
}

impl SpecExample {
    /// An example invocation shown in generated docs and help.
    pub fn new(code: impl Into<String>) -> Self {
        Self {
            code: code.into(),
            ..Default::default()
        }
    }

    /// Heading shown above the example.
    pub fn header(mut self, header: impl Into<String>) -> Self {
        self.header = Some(header.into());
        self
    }

    /// Prose shown with the example.
    pub fn help(mut self, help: impl Into<String>) -> Self {
        self.help = Some(help.into());
        self
    }

    /// Language used for syntax highlighting.
    pub fn lang(mut self, lang: impl Into<String>) -> Self {
        self.lang = lang.into();
        self
    }
}

/// Prose introducing one help section.
///
/// Keyed by the heading's title, because a section is assembled from every flag and
/// argument that names it and the text describes the section rather than any one of them.
#[derive(Debug, Default, Serialize, Clone)]
#[non_exhaustive]
pub struct SpecHeading {
    pub title: String,
    pub help: String,
}

impl SpecHeading {
    /// Prose shown between a help section's heading and its entries.
    pub fn new(title: impl Into<String>, help: impl Into<String>) -> Self {
        Self {
            title: title.into(),
            help: help.into(),
        }
    }
}

impl From<&SpecHeading> for KdlNode {
    fn from(heading: &SpecHeading) -> KdlNode {
        let mut node = KdlNode::new("heading");
        node.push(string_entry(None, &heading.title));
        node.push(string_entry(Some("help"), &heading.help));
        node
    }
}

impl From<&SpecExample> for KdlNode {
    fn from(example: &SpecExample) -> KdlNode {
        let mut node = KdlNode::new("example");
        node.push(string_entry(None, &example.code));
        if let Some(header) = &example.header {
            node.push(string_entry(Some("header"), header));
        }
        if let Some(help) = &example.help {
            node.push(string_entry(Some("help"), help));
        }
        if !example.lang.is_empty() {
            node.push(string_entry(Some("lang"), &example.lang));
        }
        node
    }
}

impl SpecCommand {
    /// Create a new builder for SpecCommand
    pub fn builder() -> SpecCommandBuilder {
        SpecCommandBuilder::new()
    }

    pub(crate) fn parse(ctx: &ParsingContext, node: &NodeHelper) -> Result<Self, UsageErr> {
        node.ensure_arg_len(1..=1)?;
        let mut cmd = Self {
            name: node.arg(0)?.ensure_string()?.to_string(),
            ..Default::default()
        };
        for (k, v) in node.props() {
            match k {
                "help" => cmd.help = Some(v.ensure_string()?),
                "long_help" => cmd.help_long = Some(v.ensure_string()?),
                "help_long" => cmd.help_long = Some(v.ensure_string()?),
                "help_md" => cmd.help_md = Some(v.ensure_string()?),
                "before_help" => cmd.before_help = Some(v.ensure_string()?),
                "before_long_help" => cmd.before_help_long = Some(v.ensure_string()?),
                "before_help_long" => cmd.before_help_long = Some(v.ensure_string()?),
                "before_help_md" => cmd.before_help_md = Some(v.ensure_string()?),
                "after_help" => cmd.after_help = Some(v.ensure_string()?),
                "after_long_help" => {
                    cmd.after_help_long = Some(v.ensure_string()?);
                }
                "after_help_long" => {
                    cmd.after_help_long = Some(v.ensure_string()?);
                }
                "after_help_md" => cmd.after_help_md = Some(v.ensure_string()?),
                "subcommand_required" => cmd.subcommand_required = v.ensure_bool()?,
                "subcommand_help_heading" => cmd.subcommand_help_heading = Some(v.ensure_string()?),
                "subcommand_value_name" => cmd.subcommand_value_name = Some(v.ensure_string()?),
                "next_line_help" => cmd.next_line_help = v.ensure_bool()?,
                "flatten_help" => cmd.flatten_help = v.ensure_bool()?,
                "term_width" => cmd.term_width = Some(v.ensure_usize()?),
                "max_term_width" => cmd.max_term_width = Some(v.ensure_usize()?),
                "external_subcommand" => cmd.external_subcommand = v.ensure_bool()?,
                "arg_required_else_help" => cmd.arg_required_else_help = v.ensure_bool()?,
                "disable_help_flag" => cmd.disable_help_flag = v.ensure_bool()?,
                "disable_help_subcommand" => cmd.disable_help_subcommand = v.ensure_bool()?,
                "disable_version_flag" => cmd.disable_version_flag = v.ensure_bool()?,
                "dont_delimit_trailing_values" => {
                    cmd.dont_delimit_trailing_values = v.ensure_bool()?
                }
                "args_override_self" => cmd.args_override_self = v.ensure_bool()?,
                "subcommand_negates_reqs" => cmd.subcommand_negates_reqs = v.ensure_bool()?,
                "args_conflicts_with_subcommands" => {
                    cmd.args_conflicts_with_subcommands = v.ensure_bool()?
                }
                "subcommand_precedence_over_arg" => {
                    cmd.subcommand_precedence_over_arg = v.ensure_bool()?
                }
                "allow_missing_positional" => cmd.allow_missing_positional = v.ensure_bool()?,
                "hide" => cmd.hide = v.ensure_bool()?,
                "help_heading" => cmd.help_heading = Some(v.ensure_string()?),
                "surface" => cmd.surface = Some(v.ensure_string()?),
                "available_if" => cmd.available_if = vec![v.ensure_string()?],
                "display_order" => cmd.display_order = Some(v.ensure_usize()?),
                "unknown_flags" => {
                    let raw = v.ensure_string()?;
                    match raw.parse() {
                        Ok(mode) => cmd.unknown_flags = Some(mode),
                        Err(_) => bail_parse!(
                            ctx,
                            v.entry.span(),
                            "unsupported unknown_flags {raw}, expected one of: {}",
                            crate::spec::unknown_flags::UNKNOWN_FLAGS_VALUES
                        ),
                    }
                }
                "effect" => {
                    let raw = v.ensure_string()?;
                    match raw.parse() {
                        Ok(effect) => cmd.effect = Some(effect),
                        Err(_) => bail_parse!(
                            ctx,
                            v.entry.span(),
                            "unsupported effect {raw}, expected one of: {EFFECT_VALUES}"
                        ),
                    }
                }
                "restart_token" => cmd.restart_token = Some(v.ensure_string()?),
                "deprecated" => {
                    cmd.deprecated = match v.value.as_bool() {
                        Some(true) => Some("deprecated".to_string()),
                        Some(false) => None,
                        None => Some(v.ensure_string()?),
                    }
                }
                "deprecated_warn_at" => cmd.deprecated_warn_at = Some(v.ensure_string()?),
                "deprecated_remove_at" => cmd.deprecated_remove_at = Some(v.ensure_string()?),
                k => bail_parse!(ctx, v.entry.span(), "unsupported cmd prop {k}"),
            }
        }
        for child in node.children() {
            match child.name() {
                "flag" => cmd.flags.push(SpecFlag::parse(ctx, &child)?),
                "use" => {
                    let at = cmd.flags.len();
                    cmd.uses.push(SpecUse::parse(ctx, &child, at)?);
                }
                "arg" => {
                    let arg = SpecArg::parse(ctx, &child)?;
                    // As on a flag: splitting a word that has room for one value would
                    // drop everything after the first separator.
                    if arg.delimiter.is_some() && !arg.var {
                        bail_parse!(
                            ctx,
                            child.node.name().span(),
                            "argument <{}> has a delimiter and holds one value; add \
                             `var=#true` for the values it splits into",
                            arg.name
                        );
                    }
                    cmd.args.push(arg);
                }
                "clause" => {
                    if cmd.clause.is_some() {
                        bail_parse!(
                            ctx,
                            child.node.name().span(),
                            "a command may declare at most one clause"
                        );
                    }
                    cmd.clause = Some(SpecClause::parse(ctx, &child)?);
                }
                "mount" => cmd.mounts.push(SpecMount::parse(ctx, &child)?),
                "group" => cmd.groups.push(SpecGroup::parse(ctx, &child)?),
                "cmd" => {
                    let node = SpecCommand::parse(ctx, &child)?;
                    cmd.subcommands.insert(node.name.to_string(), node);
                }
                "alias" => {
                    let alias = child
                        .ensure_arg_len(1..)?
                        .args()
                        .map(|e| e.ensure_string())
                        .collect::<Result<Vec<_>, _>>()?;
                    let hide = child
                        .get("hide")
                        .map(|n| n.ensure_bool())
                        .unwrap_or(Ok(false))?;
                    if hide {
                        cmd.hidden_aliases.extend(alias);
                    } else {
                        cmd.aliases.extend(alias);
                    }
                }
                "example" => {
                    let code = child.ensure_arg_len(1..=1)?.arg(0)?.ensure_string()?;
                    let mut example = SpecExample::new(code.trim().to_string());
                    for (k, v) in child.props() {
                        match k {
                            "header" => example.header = Some(v.ensure_string()?),
                            "help" => example.help = Some(v.ensure_string()?),
                            "lang" => example.lang = v.ensure_string()?,
                            k => bail_parse!(ctx, v.entry.span(), "unsupported example key {k}"),
                        }
                    }
                    cmd.examples.push(example);
                }
                "heading" => {
                    let title = child.ensure_arg_len(1..=1)?.arg(0)?.ensure_string()?;
                    let mut help = None;
                    for (k, v) in child.props() {
                        match k {
                            "help" => help = Some(v.ensure_string()?),
                            k => bail_parse!(ctx, v.entry.span(), "unsupported heading key {k}"),
                        }
                    }
                    let Some(help) = help else {
                        bail_parse!(ctx, child.node.span(), "heading {title} needs help text");
                    };
                    cmd.headings.push(SpecHeading::new(title, help));
                }
                "output" => cmd.outputs.push(SpecOutput::parse(ctx, &child)?),
                "exit_code" => cmd.exit_codes.push(SpecExitCode::parse(ctx, &child)?),
                "select" => {
                    cmd.select = Some(child.ensure_arg_len(1..=1)?.arg(0)?.ensure_string()?);
                }
                "help" => {
                    cmd.help = Some(child.ensure_arg_len(1..=1)?.arg(0)?.ensure_string()?);
                }
                "long_help" => {
                    cmd.help_long = Some(child.ensure_arg_len(1..=1)?.arg(0)?.ensure_string()?);
                }
                "help_md" => {
                    cmd.help_md = Some(child.ensure_arg_len(1..=1)?.arg(0)?.ensure_string()?);
                }
                "before_help" => {
                    cmd.before_help = Some(child.ensure_arg_len(1..=1)?.arg(0)?.ensure_string()?);
                }
                "before_long_help" => {
                    cmd.before_help_long =
                        Some(child.ensure_arg_len(1..=1)?.arg(0)?.ensure_string()?);
                }
                "before_help_md" => {
                    cmd.before_help_md =
                        Some(child.ensure_arg_len(1..=1)?.arg(0)?.ensure_string()?);
                }
                "after_help" => {
                    cmd.after_help = Some(child.ensure_arg_len(1..=1)?.arg(0)?.ensure_string()?);
                }
                "after_long_help" => {
                    cmd.after_help_long =
                        Some(child.ensure_arg_len(1..=1)?.arg(0)?.ensure_string()?);
                }
                "after_help_md" => {
                    cmd.after_help_md = Some(child.ensure_arg_len(1..=1)?.arg(0)?.ensure_string()?);
                }
                "subcommand_required" => {
                    cmd.subcommand_required = child.ensure_arg_len(1..=1)?.arg(0)?.ensure_bool()?
                }
                "help_heading" => {
                    cmd.help_heading = Some(child.ensure_arg_len(1..=1)?.arg(0)?.ensure_string()?)
                }
                "surface" => {
                    cmd.surface = Some(child.ensure_arg_len(1..=1)?.arg(0)?.ensure_string()?)
                }
                "available_if" => {
                    cmd.available_if = child
                        .ensure_arg_len(1..)?
                        .args()
                        .map(|entry| entry.ensure_string())
                        .collect::<Result<Vec<_>, _>>()?;
                }
                "subcommand_help_heading" => {
                    cmd.subcommand_help_heading =
                        Some(child.ensure_arg_len(1..=1)?.arg(0)?.ensure_string()?)
                }
                "subcommand_value_name" => {
                    cmd.subcommand_value_name =
                        Some(child.ensure_arg_len(1..=1)?.arg(0)?.ensure_string()?)
                }
                "next_line_help" => {
                    cmd.next_line_help = child.ensure_arg_len(1..=1)?.arg(0)?.ensure_bool()?
                }
                "flatten_help" => {
                    cmd.flatten_help = child.ensure_arg_len(1..=1)?.arg(0)?.ensure_bool()?
                }
                "term_width" => {
                    cmd.term_width = Some(child.ensure_arg_len(1..=1)?.arg(0)?.ensure_usize()?)
                }
                "max_term_width" => {
                    cmd.max_term_width = Some(child.ensure_arg_len(1..=1)?.arg(0)?.ensure_usize()?)
                }
                "external_subcommand" => {
                    cmd.external_subcommand = child.ensure_arg_len(1..=1)?.arg(0)?.ensure_bool()?
                }
                "arg_required_else_help" => {
                    cmd.arg_required_else_help =
                        child.ensure_arg_len(1..=1)?.arg(0)?.ensure_bool()?
                }
                "disable_help_flag" => {
                    cmd.disable_help_flag = child.ensure_arg_len(1..=1)?.arg(0)?.ensure_bool()?
                }
                "disable_help_subcommand" => {
                    cmd.disable_help_subcommand =
                        child.ensure_arg_len(1..=1)?.arg(0)?.ensure_bool()?
                }
                "disable_version_flag" => {
                    cmd.disable_version_flag = child.ensure_arg_len(1..=1)?.arg(0)?.ensure_bool()?
                }
                "dont_delimit_trailing_values" => {
                    cmd.dont_delimit_trailing_values =
                        child.ensure_arg_len(1..=1)?.arg(0)?.ensure_bool()?
                }
                "args_override_self" => {
                    cmd.args_override_self = child.ensure_arg_len(1..=1)?.arg(0)?.ensure_bool()?
                }
                "subcommand_negates_reqs" => {
                    cmd.subcommand_negates_reqs =
                        child.ensure_arg_len(1..=1)?.arg(0)?.ensure_bool()?
                }
                "args_conflicts_with_subcommands" => {
                    cmd.args_conflicts_with_subcommands =
                        child.ensure_arg_len(1..=1)?.arg(0)?.ensure_bool()?
                }
                "subcommand_precedence_over_arg" => {
                    cmd.subcommand_precedence_over_arg =
                        child.ensure_arg_len(1..=1)?.arg(0)?.ensure_bool()?
                }
                "allow_missing_positional" => {
                    cmd.allow_missing_positional =
                        child.ensure_arg_len(1..=1)?.arg(0)?.ensure_bool()?
                }
                "hide" => cmd.hide = child.ensure_arg_len(1..=1)?.arg(0)?.ensure_bool()?,
                "effect" => {
                    let arg = child.ensure_arg_len(1..=1)?.arg(0)?;
                    let raw = arg.ensure_string()?;
                    match raw.parse() {
                        Ok(effect) => cmd.effect = Some(effect),
                        Err(_) => bail_parse!(
                            ctx,
                            arg.entry.span(),
                            "unsupported effect {raw}, expected one of: {EFFECT_VALUES}"
                        ),
                    }
                }
                "restart_token" => {
                    cmd.restart_token = Some(child.ensure_arg_len(1..=1)?.arg(0)?.ensure_string()?)
                }
                "deprecated" => {
                    cmd.deprecated = match child.arg(0)?.value.as_bool() {
                        Some(true) => Some("deprecated".to_string()),
                        Some(false) => None,
                        None => Some(child.arg(0)?.ensure_string()?),
                    }
                }
                "deprecated_warn_at" => {
                    cmd.deprecated_warn_at = Some(child.arg(0)?.ensure_string()?)
                }
                "deprecated_remove_at" => {
                    cmd.deprecated_remove_at = Some(child.arg(0)?.ensure_string()?)
                }
                "complete" => {
                    let complete = SpecComplete::parse(ctx, &child)?;
                    cmd.complete.insert(complete.name.clone(), complete);
                }
                k => bail_parse!(ctx, child.node.name().span(), "unsupported cmd key {k}"),
            }
        }
        let mut sigils: Vec<&str> = Vec::new();
        for arg in &cmd.args {
            if let Some(sigil) = &arg.sigil {
                if let Some(existing) = sigils
                    .iter()
                    .find(|existing| existing.starts_with(sigil) || sigil.starts_with(**existing))
                {
                    bail_parse!(
                        ctx,
                        node.node.name().span(),
                        "argument sigils must not overlap: {existing:?} and {sigil:?}"
                    );
                }
                sigils.push(sigil);
            }
        }
        if let Some(clause) = &cmd.clause {
            if !cmd.args.is_empty() {
                bail_parse!(
                    ctx,
                    node.span(),
                    "a command cannot declare both top-level arguments and a clause"
                );
            }
            if cmd.restart_token.is_some() {
                bail_parse!(
                    ctx,
                    node.span(),
                    "a command cannot declare both restart_token and a clause"
                );
            }
            if clause.args.iter().any(|arg| arg.sigil.is_some()) {
                bail_parse!(
                    ctx,
                    node.span(),
                    "sigil arguments are not supported inside clauses"
                );
            }
            if let Some(spelling) = clause.conflicting_flag_spelling(&cmd.flags) {
                bail_parse!(
                    ctx,
                    node.span(),
                    "clause flag spelling {spelling:?} conflicts with another flag on this command"
                );
            }
        }
        Ok(cmd)
    }

    pub(crate) fn validate_sigil_prefixes(&self) -> Result<(), String> {
        fn validate(cmd: &SpecCommand, ancestors: &[String]) -> Result<(), String> {
            let mut active = ancestors.to_vec();
            for sigil in cmd.args.iter().filter_map(|arg| arg.sigil.as_ref()) {
                if let Some(existing) = active.iter().find(|existing| {
                    existing.starts_with(sigil.as_str()) || sigil.starts_with(existing.as_str())
                }) {
                    return Err(format!(
                        "argument sigils must not overlap: {existing:?} and {sigil:?}"
                    ));
                }
                active.push(sigil.clone());
            }
            for subcommand in cmd.subcommands.values() {
                validate(subcommand, &active)?;
            }
            Ok(())
        }

        validate(self, &[])
    }

    pub(crate) fn validate_clause_flag_spellings(&self) -> Result<(), String> {
        fn validate(cmd: &SpecCommand) -> Result<(), String> {
            if let Some(clause) = &cmd.clause {
                if let Some(spelling) = clause.conflicting_flag_spelling(&cmd.flags) {
                    return Err(format!(
                        "clause flag spelling {spelling:?} conflicts with another flag on this command"
                    ));
                }
            }
            for subcommand in cmd.subcommands.values() {
                validate(subcommand)?;
            }
            Ok(())
        }

        validate(self)
    }
    pub(crate) fn is_empty(&self) -> bool {
        self.args.is_empty()
            && self.clause.is_none()
            && self.flags.is_empty()
            && self.mounts.is_empty()
            && self.subcommands.is_empty()
    }
    pub fn usage(&self) -> String {
        self.usage_with_subcommands(true)
    }

    // `cli-help` only, like `SpecChoices::for_help`: the usage line without the subcommand
    // placeholder is a help-page shape, and nothing else asks for it.
    #[cfg(feature = "cli-help")]
    pub(crate) fn usage_without_subcommands(&self) -> String {
        self.usage_with_subcommands(false)
    }

    fn usage_with_subcommands(&self, include_subcommands: bool) -> String {
        let mut usage = self.full_cmd.join(" ");
        let flags = self
            .flags
            .iter()
            .filter(|f| !f.hide && !f.builtin)
            .collect_vec();
        let args = self.args.iter().filter(|a| !a.hide).collect_vec();
        if !flags.is_empty() {
            if flags.len() <= 2 {
                let inlines = flags
                    .iter()
                    .map(|f| {
                        if f.required {
                            format!("<{}>", f.usage())
                        } else {
                            format!("[{}]", f.usage())
                        }
                    })
                    .join(" ");
                usage = format!("{usage} {inlines}").trim().to_string();
            } else if flags.iter().any(|f| f.required) {
                usage = format!("{usage} <FLAGS>");
            } else {
                usage = format!("{usage} [FLAGS]");
            }
        }
        if !args.is_empty() {
            if args.len() <= 2 {
                let inlines = args.iter().map(|a| a.usage()).join(" ");
                usage = format!("{usage} {inlines}").trim().to_string();
            } else if args.iter().any(|a| a.required) {
                usage = format!("{usage} <ARGS>…");
            } else {
                usage = format!("{usage} [ARGS]…");
            }
        }
        if let Some(clause) = &self.clause {
            usage = format!("{usage} {}", clause.usage());
        }
        // TODO: mounts?
        // if !self.mounts.is_empty() {
        //     name = format!("{name} [mounts]");
        // }
        if include_subcommands && !self.subcommands.is_empty() {
            let name = self
                .subcommand_value_name
                .as_deref()
                .unwrap_or("SUBCOMMAND");
            usage = if self.subcommand_required {
                format!("{usage} <{name}>")
            } else {
                format!("{usage} [{name}]")
            };
        }
        for synopsis in self
            .mounts
            .iter()
            .filter_map(|mount| mount.synopsis.as_deref())
        {
            usage = format!("{usage} {synopsis}");
        }
        usage.trim().to_string()
    }
    /// Forget which subcommands this command was asked for.
    ///
    /// `find_subcommand` memoizes names and aliases into a `OnceLock`, so anything that adds or
    /// removes a subcommand has to say so or the lookup keeps answering for the old set.
    pub(crate) fn reset_subcommand_lookup(&mut self) {
        self.subcommand_lookup = OnceLock::new();
    }

    pub(crate) fn merge(&mut self, other: Self) {
        // Merging can add subcommands and aliases, and `find_subcommand` memoizes
        // its lookup into a OnceLock — so the cache has to go, or a name that
        // arrived here would not be findable. This worked before only because
        // mounting happened to precede the first lookup on a given command.
        self.subcommand_lookup = OnceLock::new();
        // Destructured exhaustively (no `..`) so that adding a field to
        // SpecCommand fails to compile until this decides what merging it means.
        // Runtime-derived fields are explicitly ignored rather than skipped.
        let Self {
            name,
            help,
            help_long,
            help_md,
            before_help,
            before_help_long,
            before_help_md,
            after_help,
            after_help_long,
            after_help_md,
            args,
            clause,
            flags,
            uses,
            mounts,
            groups,
            aliases,
            hidden_aliases,
            examples,
            headings,
            outputs,
            select,
            exit_codes,
            hide,
            help_heading,
            surface,
            available_if,
            display_order,
            subcommand_required,
            subcommand_help_heading,
            subcommand_value_name,
            next_line_help,
            flatten_help,
            term_width,
            max_term_width,
            external_subcommand,
            arg_required_else_help,
            disable_help_flag,
            disable_help_subcommand,
            disable_version_flag,
            dont_delimit_trailing_values,
            args_override_self,
            subcommand_negates_reqs,
            args_conflicts_with_subcommands,
            subcommand_precedence_over_arg,
            allow_missing_positional,
            restart_token,
            subcommands,
            complete,
            deprecated,
            deprecated_warn_at,
            deprecated_remove_at,
            effect,
            unknown_flags,
            // Recomputed from the merged command, never carried over.
            full_cmd: _,
            usage: _,
            mounted: _,
            flags_from_mount: _,
            subcommand_lookup: _,
        } = other;
        if !name.is_empty() {
            self.name = name;
        }
        if help.is_some() {
            self.help = help;
        }
        if help_long.is_some() {
            self.help_long = help_long;
        }
        if help_md.is_some() {
            self.help_md = help_md;
        }
        if before_help.is_some() {
            self.before_help = before_help;
        }
        if before_help_long.is_some() {
            self.before_help_long = before_help_long;
        }
        if before_help_md.is_some() {
            self.before_help_md = before_help_md;
        }
        if after_help.is_some() {
            self.after_help = after_help;
        }
        if after_help_long.is_some() {
            self.after_help_long = after_help_long;
        }
        if after_help_md.is_some() {
            self.after_help_md = after_help_md;
        }
        if !args.is_empty() {
            self.args = args;
        }
        if clause.is_some() {
            self.clause = clause;
        }
        let flags_replaced = !flags.is_empty();
        if flags_replaced {
            self.flags = flags;
        }
        // Unresolved `use` nodes travel with the flags they were written among, for the same
        // reason groups do — including when that means going with none. A `use` is a
        // declaration of flags, so whoever owns the flag list owns it: an included file that
        // replaces this command's flags replaces what it says about them, and a `use` left
        // behind would splice a set into the incoming list at a position from the old one.
        //
        // `other.uses` is normally empty either way: a spec resolves its own sets before it
        // can be merged into another, and what arrives here has been through that already.
        if flags_replaced || !uses.is_empty() {
            self.uses = uses;
        }
        if !mounts.is_empty() {
            self.mounts = mounts;
        }
        // Groups travel with the flags they name. A mounted spec that replaces this
        // command's flags replaces its groups too — including with none, which is the
        // case that matters: keeping the old set would enforce exclusivity between flags
        // that are no longer here, and a required group whose members nothing answers to
        // would reject every invocation.
        if flags_replaced || !groups.is_empty() {
            self.groups = groups;
        }
        if !aliases.is_empty() {
            self.aliases = aliases;
        }
        if !hidden_aliases.is_empty() {
            self.hidden_aliases = hidden_aliases;
        }
        if !examples.is_empty() {
            self.examples = examples;
        }
        if !headings.is_empty() {
            self.headings = headings;
        }
        // Outputs describe what the *mounted* program writes, so they move with the flags
        // rather than being folded into what was here — the same reason groups follow the
        // flags they name.
        if flags_replaced || !outputs.is_empty() {
            self.outputs = outputs;
        }
        if flags_replaced || select.is_some() {
            self.select = select;
        }
        if !exit_codes.is_empty() {
            self.exit_codes = exit_codes;
        }
        self.hide = hide;
        if help_heading.is_some() {
            self.help_heading = help_heading;
        }
        if surface.is_some() {
            self.surface = surface;
        }
        if !available_if.is_empty() {
            self.available_if = available_if;
        }
        if display_order.is_some() {
            self.display_order = display_order;
        }
        self.subcommand_required = subcommand_required;
        if subcommand_help_heading.is_some() {
            self.subcommand_help_heading = subcommand_help_heading;
        }
        if subcommand_value_name.is_some() {
            self.subcommand_value_name = subcommand_value_name;
        }
        self.next_line_help = next_line_help;
        self.flatten_help = flatten_help;
        if term_width.is_some() {
            self.term_width = term_width;
        }
        if max_term_width.is_some() {
            self.max_term_width = max_term_width;
        }
        self.external_subcommand = external_subcommand;
        self.arg_required_else_help = arg_required_else_help;
        self.disable_help_flag = disable_help_flag;
        self.disable_help_subcommand = disable_help_subcommand;
        self.disable_version_flag = disable_version_flag;
        self.dont_delimit_trailing_values = dont_delimit_trailing_values;
        self.args_override_self = args_override_self;
        self.subcommand_negates_reqs = subcommand_negates_reqs;
        self.args_conflicts_with_subcommands = args_conflicts_with_subcommands;
        self.subcommand_precedence_over_arg = subcommand_precedence_over_arg;
        self.allow_missing_positional = allow_missing_positional;
        if effect.is_some() {
            self.effect = effect;
        }
        if unknown_flags.is_some() {
            self.unknown_flags = unknown_flags;
        }
        if deprecated.is_some() {
            self.deprecated = deprecated;
        }
        if deprecated_warn_at.is_some() {
            self.deprecated_warn_at = deprecated_warn_at;
        }
        if deprecated_remove_at.is_some() {
            self.deprecated_remove_at = deprecated_remove_at;
        }
        if restart_token.is_some() {
            self.restart_token = restart_token;
        }
        for (name, cmd) in subcommands {
            self.subcommands.insert(name, cmd);
        }
        for (name, complete) in complete {
            self.complete.insert(name, complete);
        }
    }

    pub fn all_subcommands(&self) -> Vec<&SpecCommand> {
        let mut cmds = vec![];
        for cmd in self.subcommands.values() {
            cmds.push(cmd);
            cmds.extend(cmd.all_subcommands());
        }
        cmds
    }

    pub fn find_subcommand(&self, name: &str) -> Option<&SpecCommand> {
        let sl = self.subcommand_lookup.get_or_init(|| {
            let mut map = HashMap::new();
            // Names first, then aliases only where nothing answers already: a
            // command's own name outranks another command's alias, so reordering
            // `cmd` blocks cannot change which command a word selects.
            //
            // Inserting both in one pass instead let the *last* declaration win,
            // which was the opposite of what usage-argv did with the same spec —
            // it takes the first. Neither was a rule anyone had chosen.
            for name in self.subcommands.keys() {
                map.insert(name.clone(), name.clone());
            }
            for (name, cmd) in &self.subcommands {
                for alias in cmd.aliases.iter().chain(&cmd.hidden_aliases) {
                    map.entry(alias.clone()).or_insert_with(|| name.clone());
                }
            }
            map
        });
        let name = sl.get(name)?;
        self.subcommands.get(name)
    }

    pub(crate) fn mount(
        &mut self,
        global_flag_args: &[String],
        injected: Option<&HashMap<String, String>>,
    ) -> Result<(), UsageErr> {
        for mount in self.mounts.iter().cloned().collect_vec() {
            let cmd = if global_flag_args.is_empty() {
                mount.run.clone()
            } else {
                // Parse the mount command into tokens, insert global flags after the first token
                // e.g., "mise tasks ls" becomes "mise --cd dir2 tasks ls"
                // Handles quoted arguments correctly: "cmd 'arg with spaces'" stays correct
                let mut tokens = crate::shell_words::split(&mount.run)
                    .expect("mount command should be valid shell syntax");
                if !tokens.is_empty() {
                    // Insert global flags after the first token (the command name)
                    tokens.splice(1..1, global_flag_args.iter().cloned());
                }
                // Join tokens back into a properly quoted command string
                crate::shell_words::join(tokens)
            };
            let output = match injected {
                Some(outputs) => outputs
                    .get(&mount.run)
                    .cloned()
                    .ok_or_else(|| UsageErr::MissingMountOutput(mount.run.clone()))?,
                None => sh(&cmd)?,
            };
            let mut spec: Spec = output.parse()?;
            if let Some(outputs) = injected {
                // A mounted spec's root is merged into this command, so its root-only
                // default-subcommand precedence does not apply while composing mounts.
                spec.resolve_mount_outputs_at_root(outputs, false)?;
            }
            // The subcommands emitted by a mount describe another program, so mark them (and
            // everything below them) as mounted. See `SpecCommand::mounted`.
            for cmd in spec.cmd.subcommands.values_mut() {
                cmd.mark_mounted();
            }
            // `merge` folds the mounted spec's root flags into this command; remember that they
            // came from the mount. See `SpecCommand::flags_from_mount`.
            self.flags_from_mount |= !spec.cmd.flags.is_empty();
            self.merge(spec.cmd);
        }
        self.validate_clause_flag_spellings()
            .map_err(UsageErr::InvalidSpec)
    }

    /// Mark this command and all of its subcommands as coming from a mount.
    pub(crate) fn mark_mounted(&mut self) {
        self.mounted = true;
        for cmd in self.subcommands.values_mut() {
            cmd.mark_mounted();
        }
    }
}

impl From<&SpecCommand> for KdlNode {
    fn from(cmd: &SpecCommand) -> Self {
        // Destructured exhaustively (no `..`) so that adding a field to
        // SpecCommand fails to compile until this decides how to serialize it.
        let SpecCommand {
            name,
            hide,
            help_heading,
            surface,
            available_if,
            display_order,
            subcommand_required,
            subcommand_help_heading,
            subcommand_value_name,
            next_line_help,
            flatten_help,
            term_width,
            max_term_width,
            external_subcommand,
            arg_required_else_help,
            disable_help_flag,
            disable_help_subcommand,
            disable_version_flag,
            dont_delimit_trailing_values,
            args_override_self,
            subcommand_negates_reqs,
            args_conflicts_with_subcommands,
            subcommand_precedence_over_arg,
            allow_missing_positional,
            restart_token,
            unknown_flags,
            aliases,
            hidden_aliases,
            help,
            help_long,
            help_md,
            before_help,
            before_help_long,
            before_help_md,
            after_help,
            after_help_long,
            after_help_md,
            deprecated,
            deprecated_warn_at,
            deprecated_remove_at,
            effect,
            flags,
            args,
            clause,
            mounts,
            groups,
            subcommands,
            complete,
            examples,
            headings,
            outputs,
            select,
            exit_codes,
            // Resolved while the spec was read: whatever a `use` named is among `flags`
            // by now, so emitting the request too would declare those flags twice.
            uses: _,
            // Derived from the spec rather than written by it.
            full_cmd: _,
            usage: _,
            mounted: _,
            flags_from_mount: _,
            subcommand_lookup: _,
        } = cmd;
        let mut node = Self::new("cmd");
        node.entries_mut().push(name.clone().into());
        if *hide {
            node.entries_mut().push(KdlEntry::new_prop("hide", true));
        }
        if let Some(heading) = help_heading {
            node.entries_mut()
                .push(KdlEntry::new_prop("help_heading", heading.clone()));
        }
        if let Some(surface) = surface {
            node.push(KdlEntry::new_prop("surface", surface.clone()));
        }
        if !available_if.is_empty() {
            let children = node.children_mut().get_or_insert_with(KdlDocument::new);
            let mut condition = KdlNode::new("available_if");
            for value in available_if {
                condition.push(string_entry(None, value));
            }
            children.nodes_mut().push(condition);
        }
        if let Some(order) = display_order {
            node.entries_mut()
                .push(KdlEntry::new_prop("display_order", *order as i128));
        }
        if *subcommand_required {
            node.entries_mut()
                .push(KdlEntry::new_prop("subcommand_required", true));
        }
        if let Some(heading) = subcommand_help_heading {
            node.push(KdlEntry::new_prop(
                "subcommand_help_heading",
                heading.clone(),
            ));
        }
        if let Some(name) = subcommand_value_name {
            node.push(KdlEntry::new_prop("subcommand_value_name", name.clone()));
        }
        if *next_line_help {
            node.push(KdlEntry::new_prop("next_line_help", true));
        }
        if *flatten_help {
            node.push(KdlEntry::new_prop("flatten_help", true));
        }
        if let Some(width) = term_width {
            node.push(KdlEntry::new_prop("term_width", *width as i128));
        }
        if let Some(width) = max_term_width {
            node.push(KdlEntry::new_prop("max_term_width", *width as i128));
        }
        if *external_subcommand {
            node.entries_mut()
                .push(KdlEntry::new_prop("external_subcommand", true));
        }
        if *arg_required_else_help {
            node.entries_mut()
                .push(KdlEntry::new_prop("arg_required_else_help", true));
        }
        if *disable_help_flag {
            node.push(KdlEntry::new_prop("disable_help_flag", true));
        }
        if *disable_help_subcommand {
            node.push(KdlEntry::new_prop("disable_help_subcommand", true));
        }
        if *disable_version_flag {
            node.push(KdlEntry::new_prop("disable_version_flag", true));
        }
        if *dont_delimit_trailing_values {
            node.entries_mut()
                .push(KdlEntry::new_prop("dont_delimit_trailing_values", true));
        }
        if !*args_override_self {
            node.push(KdlEntry::new_prop("args_override_self", false));
        }
        if *subcommand_negates_reqs {
            node.push(KdlEntry::new_prop("subcommand_negates_reqs", true));
        }
        if *args_conflicts_with_subcommands {
            node.push(KdlEntry::new_prop("args_conflicts_with_subcommands", true));
        }
        if *subcommand_precedence_over_arg {
            node.push(KdlEntry::new_prop("subcommand_precedence_over_arg", true));
        }
        if *allow_missing_positional {
            node.push(KdlEntry::new_prop("allow_missing_positional", true));
        }
        if let Some(restart_token) = &restart_token {
            node.entries_mut()
                .push(KdlEntry::new_prop("restart_token", restart_token.clone()));
        }
        if !aliases.is_empty() {
            let mut alias_node = KdlNode::new("alias");
            for alias in aliases {
                alias_node.entries_mut().push(alias.clone().into());
            }
            let children = node.children_mut().get_or_insert_with(KdlDocument::new);
            children.nodes_mut().push(alias_node);
        }
        if !hidden_aliases.is_empty() {
            let mut alias_node = KdlNode::new("alias");
            for alias in hidden_aliases {
                alias_node.entries_mut().push(alias.clone().into());
            }
            alias_node
                .entries_mut()
                .push(KdlEntry::new_prop("hide", true));
            let children = node.children_mut().get_or_insert_with(KdlDocument::new);
            children.nodes_mut().push(alias_node);
        }
        if let Some(help) = &help {
            node.entries_mut().push(string_entry(Some("help"), help));
        }
        if let Some(help) = &help_long {
            let children = node.children_mut().get_or_insert_with(KdlDocument::new);
            let mut node = KdlNode::new("long_help");
            node.push(string_entry(None, help));
            children.nodes_mut().push(node);
        }
        if let Some(help) = &help_md {
            let children = node.children_mut().get_or_insert_with(KdlDocument::new);
            let mut node = KdlNode::new("help_md");
            node.push(string_entry(None, help));
            children.nodes_mut().push(node);
        }
        if let Some(help) = &before_help {
            node.entries_mut()
                .push(string_entry(Some("before_help"), help));
        }
        if let Some(help) = &before_help_long {
            let children = node.children_mut().get_or_insert_with(KdlDocument::new);
            let mut node = KdlNode::new("before_long_help");
            node.push(string_entry(None, help));
            children.nodes_mut().push(node);
        }
        if let Some(help) = &before_help_md {
            let children = node.children_mut().get_or_insert_with(KdlDocument::new);
            let mut node = KdlNode::new("before_help_md");
            node.push(string_entry(None, help));
            children.nodes_mut().push(node);
        }
        if let Some(help) = &after_help {
            node.entries_mut()
                .push(string_entry(Some("after_help"), help));
        }
        if let Some(help) = &after_help_long {
            let children = node.children_mut().get_or_insert_with(KdlDocument::new);
            let mut node = KdlNode::new("after_long_help");
            node.push(string_entry(None, help));
            children.nodes_mut().push(node);
        }
        if let Some(help) = &after_help_md {
            let children = node.children_mut().get_or_insert_with(KdlDocument::new);
            let mut node = KdlNode::new("after_help_md");
            node.push(string_entry(None, help));
            children.nodes_mut().push(node);
        }
        if let Some(deprecated) = &deprecated {
            node.entries_mut()
                .push(string_entry(Some("deprecated"), deprecated));
        }
        if let Some(at) = deprecated_warn_at {
            node.push(string_entry(Some("deprecated_warn_at"), at));
        }
        if let Some(at) = deprecated_remove_at {
            node.push(string_entry(Some("deprecated_remove_at"), at));
        }
        if let Some(effect) = effect {
            node.entries_mut()
                .push(string_entry(Some("effect"), effect.as_str()));
        }
        if let Some(unknown_flags) = unknown_flags {
            node.entries_mut()
                .push(string_entry(Some("unknown_flags"), unknown_flags.as_str()));
        }
        for flag in flags {
            let children = node.children_mut().get_or_insert_with(KdlDocument::new);
            children.nodes_mut().push(flag.into());
        }
        for arg in args {
            let children = node.children_mut().get_or_insert_with(KdlDocument::new);
            children.nodes_mut().push(arg.into());
        }
        if let Some(clause) = clause {
            let children = node.children_mut().get_or_insert_with(KdlDocument::new);
            children.nodes_mut().push(clause.into());
        }
        for mount in mounts {
            let children = node.children_mut().get_or_insert_with(KdlDocument::new);
            children.nodes_mut().push(mount.into());
        }
        // After the flags they name, so a reader meets the members before the rule
        // about them.
        for group in groups {
            let children = node.children_mut().get_or_insert_with(KdlDocument::new);
            children.nodes_mut().push(group.into());
        }
        for cmd in subcommands.values() {
            let children = node.children_mut().get_or_insert_with(KdlDocument::new);
            children.nodes_mut().push(cmd.into());
        }
        for example in examples {
            let children = node.children_mut().get_or_insert_with(KdlDocument::new);
            children.nodes_mut().push(example.into());
        }
        for heading in headings {
            let children = node.children_mut().get_or_insert_with(KdlDocument::new);
            children.nodes_mut().push(heading.into());
        }
        // Outputs before the flag that picks among them, so a reader meets the things
        // being chosen before the rule for choosing — the same order groups follow.
        for output in outputs {
            let children = node.children_mut().get_or_insert_with(KdlDocument::new);
            children.nodes_mut().push(output.into());
        }
        if let Some(select) = select {
            let mut select_node = KdlNode::new("select");
            select_node.push(string_entry(None, select));
            let children = node.children_mut().get_or_insert_with(KdlDocument::new);
            children.nodes_mut().push(select_node);
        }
        for exit_code in exit_codes {
            let children = node.children_mut().get_or_insert_with(KdlDocument::new);
            children.nodes_mut().push(exit_code.into());
        }
        for complete in complete.values() {
            let children = node.children_mut().get_or_insert_with(KdlDocument::new);
            children.nodes_mut().push(complete.into());
        }
        node
    }
}

#[cfg(feature = "clap")]
impl From<&clap::Command> for SpecCommand {
    fn from(cmd: &clap::Command) -> Self {
        let mut spec = Self {
            name: cmd.get_name().to_string(),
            hide: cmd.is_hide_set(),
            help: cmd.get_about().map(|s| s.to_string()),
            help_long: cmd.get_long_about().map(|s| s.to_string()),
            before_help: cmd.get_before_help().map(|s| s.to_string()),
            before_help_long: cmd.get_before_long_help().map(|s| s.to_string()),
            after_help: cmd.get_after_help().map(|s| s.to_string()),
            after_help_long: cmd.get_after_long_help().map(|s| s.to_string()),
            ..Default::default()
        };
        // What clap would do with a dash-word it does not recognize, said out loud.
        //
        // clap rejects one; this spec's default is to offer it to the positionals, because a
        // spec also describes wrappers — a script run through `usage exec`, a task's arguments —
        // where a dash-word is data in transit rather than a mistake. A CLI generated *from
        // clap*, though, is not one of those: clap already decided, and saying nothing here
        // silently loosened every command it described. mise's spec has 211 commands and not one
        // of them said `unknown_flags`, so `mise use --globa` became a tool named `--globa`
        // rather than the error clap gives.
        //
        // Which commands forward unknown *flags* is clap's own knowledge: an argument that
        // accepts hyphen values, or a trailing var arg. In mise that is five commands —
        // `run`, `watch`, `asdf`, `tool-stub` and the root's implicit task arguments — and
        // the other two hundred get the stricter reading back.
        //
        // An external subcommand is a different shape: an unmatched *word* is forwarded with
        // the rest of argv. clap still rejects an unknown flag on such a command (`x --wat`),
        // so mapping `allow_external_subcommands` onto `unknown_flags=value` silently loosened
        // every clap CLI that allowed one.
        spec.external_subcommand = cmd.is_allow_external_subcommands_set();
        let forwards = cmd
            .get_arguments()
            .any(|arg| arg.is_allow_hyphen_values_set() || arg.is_trailing_var_arg_set());
        spec.unknown_flags = Some(if forwards {
            UnknownFlags::Value
        } else {
            UnknownFlags::Error
        });

        for alias in cmd.get_visible_aliases() {
            spec.aliases.push(alias.to_string());
        }
        for alias in cmd.get_all_aliases() {
            if spec.aliases.contains(&alias.to_string()) {
                continue;
            }
            spec.hidden_aliases.push(alias.to_string());
        }
        for arg in cmd.get_arguments() {
            let complete_type = crate::spec::arg::value_hint_type(arg.get_value_hint());
            let conflicts: Vec<String> = cmd
                .get_arg_conflicts_with(arg)
                .iter()
                .filter_map(|other| match (other.get_long(), other.get_short()) {
                    (Some(long), _) => Some(format!("--{long}")),
                    (None, Some(short)) => Some(format!("-{short}")),
                    (None, None) if other.is_positional() => Some(SpecArg::from(*other).name),
                    (None, None) => None,
                })
                .collect();
            if arg.is_positional() {
                let mut positional: SpecArg = arg.into();
                positional.allow_negative_numbers |= cmd.is_allow_negative_numbers_set();
                positional.conflicts = conflicts;
                if let Some(type_) = complete_type {
                    let name = positional.name.to_lowercase();
                    spec.complete.insert(
                        name.clone(),
                        SpecComplete {
                            name,
                            type_: Some(type_.to_string()),
                            ..Default::default()
                        },
                    );
                }
                spec.args.push(positional)
            } else {
                let mut flag: SpecFlag = arg.into();
                if let Some(value) = &mut flag.arg {
                    value.allow_negative_numbers |= cmd.is_allow_negative_numbers_set();
                }
                // clap keeps conflicts on the command rather than on the argument, so
                // this is the only place both are in view. Written with dashes,
                // matching how the spec refers to a flag everywhere else.
                //
                // A short-only flag is named `-s`, which selectors accept as readily as
                // `--long`: taking only the long form would have dropped the conflict
                // and let the spec accept a combination clap rejects.
                flag.conflicts = conflicts;
                if let (Some(type_), Some(value)) = (complete_type, flag.arg.as_ref()) {
                    let name = value.name.to_lowercase();
                    spec.complete.insert(
                        name.clone(),
                        SpecComplete {
                            name,
                            type_: Some(type_.to_string()),
                            ..Default::default()
                        },
                    );
                }
                spec.flags.push(flag)
            }
        }
        // clap assigns an implicit monotonically increasing order to arguments. Emitting
        // that number for every ordinary declaration makes generated specs noisy without
        // changing presentation, since usage already retains declaration order. Keep the
        // values only when they actually reorder a section.
        if spec
            .args
            .windows(2)
            .all(|pair| pair[0].display_order <= pair[1].display_order)
        {
            for arg in &mut spec.args {
                arg.display_order = None;
            }
        }
        if spec
            .flags
            .windows(2)
            .all(|pair| pair[0].display_order <= pair[1].display_order)
        {
            for flag in &mut spec.flags {
                flag.display_order = None;
            }
        }
        // Groups, which clap does expose — `get_groups`, and `get_args` on each. A group
        // names its members by clap's internal id, so each is resolved back to the flag it
        // points at and written as a selector, the way conflicts are just above.
        //
        // clap's own `--help` groups (`ArgGroup` ids it creates for its built-in flags)
        // have no members of ours in them, so the two-member floor drops them naturally
        // rather than needing a name check.
        for group in cmd.get_groups() {
            let members: Vec<String> = group
                .get_args()
                .filter_map(|id| cmd.get_arguments().find(|arg| arg.get_id() == id))
                .filter_map(|arg| match (arg.get_long(), arg.get_short()) {
                    (Some(long), _) => Some(format!("--{long}")),
                    (None, Some(short)) => Some(format!("-{short}")),
                    (None, None) if arg.is_positional() => Some(SpecArg::from(arg).name),
                    (None, None) => None,
                })
                .collect();
            // Below two members there is no rule left to enforce: whatever the group said
            // about "at most one" or "at least one" is either vacuous or is plain
            // required-ness on the single flag, which the flag already carries.
            if members.len() < 2 {
                continue;
            }
            // `multiple` without `required` enforces nothing at all — any number of
            // members, none of them needed — so there is nothing to carry across.
            //
            // This is not a corner case. clap's *derive* emits exactly that group for
            // every `#[derive(Args)]` struct, named after the struct and holding all its
            // fields, to make `flatten` work: `clap_derive`'s `args.rs` builds
            // `ArgGroup::new(id).multiple(true)`. Carrying them would put a `group Lint
            // …` in the spec of every clap-derived CLI, including this repository's own,
            // describing bookkeeping rather than a rule anyone declared.
            let required = group.is_required_set();
            // `is_multiple` takes `&mut self` in clap, and a `&ArgGroup` is all a
            // `Command` hands out — so the group is cloned to ask. Once per group at
            // spec-generation time, which is a build step rather than a parse.
            let multiple = group.clone().is_multiple();
            if multiple && !required {
                continue;
            }
            let mut spec_group = SpecGroup::new(group.get_id().as_str(), members);
            spec_group.required = required;
            spec_group.multiple = multiple;
            spec.groups.push(spec_group);
        }
        spec.subcommand_required = cmd.is_subcommand_required_set();
        spec.subcommand_help_heading = cmd.get_subcommand_help_heading().map(str::to_string);
        spec.subcommand_value_name = cmd.get_subcommand_value_name().map(str::to_string);
        spec.next_line_help = cmd.is_next_line_help_set();
        spec.flatten_help = cmd.is_flatten_help_set();
        spec.arg_required_else_help = cmd.is_arg_required_else_help_set();
        spec.disable_help_flag = cmd.is_disable_help_flag_set();
        spec.disable_help_subcommand =
            cmd.get_subcommands().next().is_some() && cmd.is_disable_help_subcommand_set();
        spec.disable_version_flag = (cmd.get_version().is_some()
            || cmd.get_long_version().is_some())
            && cmd.is_disable_version_flag_set();
        spec.dont_delimit_trailing_values = cmd.is_dont_delimit_trailing_values_set();
        spec.args_override_self = cmd.is_args_override_self();
        spec.subcommand_negates_reqs = cmd.is_subcommand_negates_reqs_set();
        spec.args_conflicts_with_subcommands = cmd.is_args_conflicts_with_subcommands_set();
        spec.subcommand_precedence_over_arg = cmd.is_subcommand_precedence_over_arg_set();
        spec.allow_missing_positional = cmd.is_allow_missing_positional_set();
        for subcmd in cmd.get_subcommands() {
            let mut scmd: SpecCommand = subcmd.into();
            scmd.name = subcmd.get_name().to_string();
            scmd.display_order = Some(subcmd.get_display_order());
            spec.subcommands.insert(scmd.name.clone(), scmd);
        }
        // 999 is clap's ordinary subcommand order. Leaving every command at that value lets
        // usage's existing alphabetical tie-breaker produce the same page without serializing
        // redundant metadata.
        if spec
            .subcommands
            .iter()
            .all(|(_, subcommand)| subcommand.display_order == Some(999))
        {
            for (_, subcommand) in &mut spec.subcommands {
                subcommand.display_order = None;
            }
        }
        spec
    }
}

#[cfg(feature = "clap")]
impl From<clap::Command> for Spec {
    fn from(cmd: clap::Command) -> Self {
        (&cmd).into()
    }
}

#[cfg(test)]
mod tests {
    use crate::spec::effect::SpecCommandEffect;
    use crate::Spec;
    use insta::assert_snapshot;

    #[test]
    fn overlapping_sigils_are_rejected_on_one_command_and_across_subcommands() {
        for spec in [
            r#"bin "ex"
arg "[short]..." sigil="+"
arg "[long]..." sigil="++"
"#,
            r#"bin "ex"
arg "[short]..." sigil="+"
cmd "run" { arg "[long]..." sigil="++" }
"#,
        ] {
            let error = Spec::parse(&Default::default(), spec).unwrap_err();
            assert!(
                format!("{error:?}").contains("argument sigils must not overlap"),
                "{error:?}"
            );
        }
    }

    #[test]
    fn test_effect_prop_and_child_node() {
        let spec = Spec::parse(
            &Default::default(),
            r#"
bin "mise"
cmd "ls" effect="read"
cmd "use" effect="write"
cmd "uninstall" {
    effect "destructive"
}
cmd "version"
            "#,
        )
        .unwrap();

        let cmds = &spec.cmd.subcommands;
        assert_eq!(cmds["ls"].effect, Some(SpecCommandEffect::Read));
        assert_eq!(cmds["use"].effect, Some(SpecCommandEffect::Write));
        assert_eq!(
            cmds["uninstall"].effect,
            Some(SpecCommandEffect::Destructive)
        );
        // Unspecified stays unknown rather than defaulting to anything.
        assert_eq!(cmds["version"].effect, None);
    }

    #[test]
    fn test_effect_is_not_inherited_by_subcommands() {
        let spec = Spec::parse(
            &Default::default(),
            r#"
bin "git"
cmd "remote" effect="read" {
    cmd "add" effect="write"
    cmd "show"
}
            "#,
        )
        .unwrap();

        let remote = &spec.cmd.subcommands["remote"];
        assert_eq!(remote.effect, Some(SpecCommandEffect::Read));
        assert_eq!(
            remote.subcommands["add"].effect,
            Some(SpecCommandEffect::Write)
        );
        assert_eq!(remote.subcommands["show"].effect, None);
    }

    #[test]
    fn test_effect_roundtrips_through_kdl() {
        let spec = Spec::parse(
            &Default::default(),
            r#"
bin "mise"
cmd "ls" effect="read"
cmd "uninstall" effect="destructive"
            "#,
        )
        .unwrap();

        assert_snapshot!(spec, @r#"
        name mise
        bin mise
        cmd ls effect=read
        cmd uninstall effect=destructive
        "#);
    }

    /// `merge` is how included and mounted specs are composed onto a command.
    /// It has to treat `effect` the way it treats every other optional field:
    /// an overlay that says nothing must not erase what is already declared.
    #[test]
    fn test_effect_survives_merge() {
        let cmd_with = |src: &str| {
            Spec::parse(&Default::default(), src)
                .unwrap()
                .cmd
                .subcommands["uninstall"]
                .clone()
        };

        let declared = cmd_with(r#"cmd "uninstall" effect="destructive""#);
        let silent = cmd_with(r#"cmd "uninstall" help="Remove a tool""#);
        let contradicting = cmd_with(r#"cmd "uninstall" effect="write""#);

        let mut cmd = declared.clone();
        cmd.merge(silent);
        assert_eq!(cmd.effect, Some(SpecCommandEffect::Destructive));

        let mut cmd = declared;
        cmd.merge(contradicting);
        assert_eq!(cmd.effect, Some(SpecCommandEffect::Write));
    }

    #[test]
    fn test_unknown_effect_is_an_error() {
        let err = Spec::parse(
            &Default::default(),
            r#"
bin "mise"
cmd "ls" effect="readonly"
            "#,
        )
        .unwrap_err();
        assert!(
            err.to_string().contains("Invalid usage config"),
            "unexpected error: {err}"
        );
    }
}

#[cfg(test)]
mod merge_tests {
    use crate::Spec;

    fn uninstall(src: &str) -> crate::SpecCommand {
        Spec::parse(&Default::default(), src)
            .unwrap()
            .cmd
            .subcommands["uninstall"]
            .clone()
    }

    /// An overlay that says nothing about deprecation must not un-deprecate a
    /// command that already declared it.
    #[test]
    fn test_deprecated_survives_merge() {
        let declared = uninstall(r#"cmd "uninstall" deprecated="use `remove`""#);
        let silent = uninstall(r#"cmd "uninstall" help="Remove a tool""#);
        let contradicting = uninstall(r#"cmd "uninstall" deprecated="gone in v3""#);

        let mut cmd = declared.clone();
        cmd.merge(silent);
        assert_eq!(cmd.deprecated.as_deref(), Some("use `remove`"));

        let mut cmd = declared;
        cmd.merge(contradicting);
        assert_eq!(cmd.deprecated.as_deref(), Some("gone in v3"));
    }

    #[test]
    fn mounted_flags_replace_outputs_and_their_selector() {
        let mut mounting = uninstall(
            r#"cmd "uninstall" { flag "--format <FORMAT>"; output "json" framing="json"; select "--format" }"#,
        );
        let mounted = uninstall(r#"cmd "uninstall" { flag "--quiet" }"#);

        mounting.merge(mounted);

        assert!(mounting.outputs.is_empty());
        assert!(mounting.select.is_none());
    }
}

#[cfg(test)]
mod roundtrip_tests {
    use crate::kdl;
    use crate::Spec;

    /// Serializing a spec back to KDL and reparsing it must not lose anything.
    ///
    /// The parser is a match on node names, so exhaustive destructuring can't
    /// catch a field the serializer knows about but the parser doesn't, or the
    /// reverse. Comparing the serde representation covers every field without
    /// this test having to enumerate them, so a new field is covered the day it
    /// is added.
    #[test]
    fn test_spec_survives_a_kdl_roundtrip() {
        let src = r#"
name "My CLI"
bin "mycli"
about "does things"
version "1.0.0"
author "nobody"
license "MIT"

flag "-v --verbose" help="Verbose logging" global=#true count=#true
arg "<dir>" help="Directory to use"

cmd "install" help="Install a package" subcommand_required=#false {
    alias "i"
    alias "add" hide=#true
    long_help "The long help for install"
    help_md "The **markdown** help for install"
    before_help "before"
    before_long_help "The long before-help for install"
    before_help_md "The **markdown** before-help for install"
    after_help "after"
    after_long_help "The long after-help for install"
    after_help_md "The **markdown** after-help for install"
    arg "<pkg>" help="Package to install"
    arg "[dest]" effect="write"
    flag "-f --force" help="Overwrite"
    flag "--purge" effect="destructive" overrides="-f" required_unless="--keep"
    flag "--format <FMT>" help="Output format"
    complete "pkg" run="mycli list --available" descriptions=#true
    example "mycli install foo" header="Install foo" help="Installs foo" lang="sh"
    example "mycli install bar"
    heading "Output" help="Formats are stable across releases."
    output "human" default=#true help="A progress log"
    output "json" framing="json" help="One report object" {
        schema "{\n  \"type\": \"object\"\n}"
    }
    select "--format"
    exit_code 0 "installed"
    exit_code 1 "the package was not found"
    cmd "from" help="Install from a source" {
        arg "<src>"
    }
}
cmd "wrapped" help="Wraps another CLI" {
    mount run="mycli plugin usage-spec"
}
cmd "remove" help="Remove a package" deprecated="use `uninstall`" effect="destructive"
cmd "run" restart_token=":::" help="Run tasks"
cmd "exec" external_subcommand=#true help="Run an external command"
cmd "hidden" hide=#true
        "#;

        let original = Spec::parse(&Default::default(), src).unwrap();
        let reparsed = Spec::parse(&Default::default(), &original.to_string()).unwrap();

        let original = serde_json::to_value(&original).unwrap();
        let reparsed = serde_json::to_value(&reparsed).unwrap();
        pretty_assertions::assert_eq!(original, reparsed);

        // Equality is only meaningful if the fixture actually populated the
        // fields, so guard against a future edit quietly emptying it out.
        let install = &original["cmd"]["subcommands"]["install"];
        let purge = install["flags"]
            .as_array()
            .unwrap()
            .iter()
            .find(|flag| flag["name"] == "purge")
            .unwrap();
        assert_eq!(purge["overrides"], serde_json::json!(["-f"]));
        assert_eq!(purge["required_unless"], serde_json::json!(["--keep"]));
        for key in [
            "help_long",
            "help_md",
            "before_help",
            "before_help_long",
            "before_help_md",
            "after_help",
            "after_help_long",
            "after_help_md",
            "deprecated",
            "effect",
            "restart_token",
            "examples",
            "headings",
            "complete",
            "mounts",
            "aliases",
            "hidden_aliases",
            "outputs",
            "select",
            "exit_codes",
        ] {
            let populated = match key {
                // These sit on other commands in the fixture.
                "deprecated" | "effect" => {
                    original["cmd"]["subcommands"]["remove"].get(key).is_some()
                }
                "restart_token" => original["cmd"]["subcommands"]["run"].get(key).is_some(),
                "mounts" => !original["cmd"]["subcommands"]["wrapped"]["mounts"]
                    .as_array()
                    .unwrap()
                    .is_empty(),
                _ => match install.get(key) {
                    Some(serde_json::Value::Array(a)) => !a.is_empty(),
                    Some(serde_json::Value::Object(o)) => !o.is_empty(),
                    Some(_) => true,
                    None => false,
                },
            };
            assert!(populated, "fixture does not exercise `{key}`");
        }

        // Flag- and arg-level effects live one level down, so check them
        // explicitly rather than by name against the command object.
        assert!(
            install["flags"]
                .as_array()
                .unwrap()
                .iter()
                .any(|f| f.get("effect").is_some()),
            "fixture does not exercise a flag-level `effect`"
        );
        assert!(
            install["args"]
                .as_array()
                .unwrap()
                .iter()
                .any(|a| a.get("effect").is_some()),
            "fixture does not exercise an arg-level `effect`"
        );
    }
    #[cfg(feature = "clap")]
    #[test]
    fn a_clap_command_says_what_clap_would_do_with_an_unknown_flag() {
        use super::{SpecCommand, UnknownFlags};

        // clap rejects a dash-word it does not know; this spec's default is to offer it to the
        // positionals. Saying nothing therefore loosened every command generated from clap —
        // which is how `mise use --globa` became a tool named `--globa` rather than an error.
        let plain = clap::Command::new("build")
            .arg(clap::Arg::new("target").required(false))
            .arg(clap::Arg::new("force").long("force").num_args(0));
        let spec: SpecCommand = (&plain).into();
        assert_eq!(spec.unknown_flags, Some(UnknownFlags::Error));

        // A command that forwards says so, and clap is the one that knows: an argument taking
        // hyphen values is what a wrapper looks like.
        let wrapper = clap::Command::new("run").arg(
            clap::Arg::new("args")
                .num_args(0..)
                .allow_hyphen_values(true),
        );
        let spec: SpecCommand = (&wrapper).into();
        assert_eq!(spec.unknown_flags, Some(UnknownFlags::Value));

        // As does one whose trailing argument swallows the rest.
        let trailing = clap::Command::new("exec").arg(
            clap::Arg::new("cmd")
                .num_args(0..)
                .trailing_var_arg(true)
                .allow_hyphen_values(true),
        );
        let spec: SpecCommand = (&trailing).into();
        assert_eq!(spec.unknown_flags, Some(UnknownFlags::Value));

        // And a command that takes whatever subcommand it is given, which is a different
        // shape from forwarding unknown flags: clap still rejects `x --wat`.
        let external = clap::Command::new("x").allow_external_subcommands(true);
        let spec: SpecCommand = (&external).into();
        assert_eq!(spec.unknown_flags, Some(UnknownFlags::Error));
        assert!(spec.external_subcommand);
    }

    #[cfg(feature = "clap")]
    #[test]
    fn the_decision_survives_being_written_and_read_back() {
        use super::SpecCommand;

        // The point of setting it is what a *parser* does with the spec afterwards, so the round
        // trip is what makes it true rather than the field.
        let plain = clap::Command::new("build").arg(clap::Arg::new("target").required(false));
        let spec: SpecCommand = (&plain).into();
        let node: kdl::KdlNode = (&spec).into();
        let kdl = node.to_string();
        assert!(kdl.contains("unknown_flags=error"), "{kdl}");
    }

    #[cfg(feature = "clap")]
    #[test]
    fn the_clap_bridge_preserves_args_override_self() {
        use super::SpecCommand;

        let strict: SpecCommand = (&clap::Command::new("strict")).into();
        assert!(!strict.args_override_self, "clap is strict by default");

        let permissive: SpecCommand =
            (&clap::Command::new("permissive").args_override_self(true)).into();
        assert!(permissive.args_override_self);

        let node: kdl::KdlNode = (&strict).into();
        assert!(node.to_string().contains("args_override_self=#false"));
    }

    #[cfg(feature = "clap")]
    #[test]
    fn the_clap_bridge_preserves_subcommand_presentation() {
        use super::SpecCommand;

        let spec: SpecCommand = (&clap::Command::new("ex")
            .subcommand(clap::Command::new("run"))
            .subcommand_help_heading("Actions")
            .subcommand_value_name("ACTION"))
            .into();
        assert_eq!(spec.subcommand_help_heading.as_deref(), Some("Actions"));
        assert_eq!(spec.subcommand_value_name.as_deref(), Some("ACTION"));
        let node: kdl::KdlNode = (&spec).into();
        let kdl = node.to_string();
        assert!(kdl.contains("subcommand_help_heading=Actions"), "{kdl}");
        assert!(kdl.contains("subcommand_value_name=ACTION"), "{kdl}");
    }

    #[cfg(feature = "clap")]
    #[test]
    fn the_clap_bridge_preserves_subcommand_negates_requirements() {
        use super::SpecCommand;

        let spec: SpecCommand = (&clap::Command::new("ex").subcommand_negates_reqs(true)).into();
        assert!(spec.subcommand_negates_reqs);
        let node: kdl::KdlNode = (&spec).into();
        assert!(node.to_string().contains("subcommand_negates_reqs=#true"));
    }

    #[cfg(feature = "clap")]
    #[test]
    fn the_clap_bridge_preserves_argument_subcommand_conflicts() {
        use super::SpecCommand;

        let spec: SpecCommand =
            (&clap::Command::new("ex").args_conflicts_with_subcommands(true)).into();
        assert!(spec.args_conflicts_with_subcommands);
        let node: kdl::KdlNode = (&spec).into();
        assert!(node
            .to_string()
            .contains("args_conflicts_with_subcommands=#true"));
    }

    #[cfg(feature = "clap")]
    #[test]
    fn the_clap_bridge_preserves_allow_missing_positional() {
        use super::SpecCommand;

        let spec: SpecCommand = (&clap::Command::new("ex").allow_missing_positional(true)).into();
        assert!(spec.allow_missing_positional);
        let node: kdl::KdlNode = (&spec).into();
        assert!(node.to_string().contains("allow_missing_positional=#true"));
    }
}