everruns_cli_contract/

lib.rs

//! The `everruns` command-line contract: one grammar, shared by the CLI and
//! the agent-facing command tree.
//!
//! A caller learns one CLI. What a person types in a terminal and what an
//! agent types in its shell are the same words, with the same flags, the same
//! short options, the same positionals and the same help. That only stays true
//! if there is one definition, so this crate is it: the grammar as data, and
//! the single function that turns it into a [`clap::Command`].
//!
//! It is part of the [Everruns](https://everruns.com) ecosystem and is consumed
//! by `everruns-cli` and by the server's agent-facing command tree.
//!
//! # Example
//!
//! ```
//! use everruns_cli_contract::{ArgKind, ContractArg, ContractCommand, ContractExample};
//!
//! let command = ContractCommand {
//!     wire_name: "list_agents".into(),
//!     path: vec!["agents".into()],
//!     verb: "list".into(),
//!     description: "List agents in the organization.".into(),
//!     method: "GET".into(),
//!     http_path: "/v1/agents".into(),
//!     args: vec![ContractArg {
//!         field: "limit".into(),
//!         long: "limit".into(),
//!         short: None,
//!         position: None,
//!         kind: ArgKind::Integer,
//!         required: false,
//!         help: Some("Maximum rows to return.".into()),
//!         choices: vec![],
//!     }],
//!     examples: vec![ContractExample {
//!         intent: "List the ten most recent agents".into(),
//!         command: "everruns agents list --limit 10".into(),
//!     }],
//! };
//!
//! assert_eq!(command.spelling(), "agents list");
//! assert!(command.after_help().contains("List the ten most recent agents:"));
//! ```

#![cfg_attr(test, allow(clippy::unwrap_used, clippy::expect_used))]

use clap::builder::{BoolishValueParser, PossibleValuesParser};
use clap::{Arg, ArgAction, ColorChoice, Command};
use serde::{Deserialize, Serialize};

/// What one argument accepts.
///
/// A reduction of JSON Schema to the shapes a command line has: everything
/// else is passed as one JSON document, because a shell argument is text and
/// pretending otherwise only moves the parse somewhere less helpful.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
#[serde(rename_all = "snake_case")]
pub enum ArgKind {
    /// A switch. Accepts `--flag` and `--flag true`, because callers write
    /// both and one of them erroring is a round trip spent on syntax.
    Boolean,
    Integer,
    Number,
    String,
    /// Repeatable, and comma-splittable when the items are scalars.
    StringList,
    IntegerList,
    /// An object or array of objects: one JSON document.
    Json,
}

/// One argument of one command.
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
pub struct ContractArg {
    /// Parameter name as the command deserializes it, e.g. `system_prompt`.
    /// This is what dispatch sends, whatever the caller typed.
    pub field: String,
    /// Long spelling, without dashes, e.g. `system-prompt`.
    pub long: String,
    /// Short spelling, when the command declares one.
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub short: Option<char>,
    /// Position when this argument is also spelled as a bare word, 1-based.
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub position: Option<usize>,
    pub kind: ArgKind,
    #[serde(default)]
    pub required: bool,
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub help: Option<String>,
    /// Declared values, surfaced so help lists them and a wrong one is
    /// corrected rather than dispatched.
    #[serde(default, skip_serializing_if = "Vec::is_empty")]
    pub choices: Vec<String>,
}

/// One worked example, in the shape yolop's commands use: a line saying what
/// the caller is trying to do, then the command that does it.
///
/// Both halves matter, and a bare command line is the half that gets written
/// when the type does not ask for the other. `yolop sessions search --query X`
/// tells a reader the syntax they could have guessed; "Search prior sessions
/// for an exact marker" tells them when to reach for it. An agent reading
/// `--help` is choosing between commands, not recalling one it already knows.
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
pub struct ContractExample {
    /// What this invocation accomplishes, as a phrase. No trailing period:
    /// the renderer adds the colon.
    pub intent: String,
    /// The complete, runnable command line.
    pub command: String,
}

/// One command: where it sits, what it is called on the wire, how it is
/// reached over HTTP, and what it accepts.
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
pub struct ContractCommand {
    /// Canonical identity, e.g. `list_agents`.
    pub wire_name: String,
    /// Noun path from the root, e.g. `["agents", "versions"]`.
    pub path: Vec<String>,
    /// Leaf verb, e.g. `list`.
    pub verb: String,
    pub description: String,
    /// HTTP method and path template, so a consumer holding only an API client
    /// can run the command without a hand-written implementation for it.
    pub method: String,
    pub http_path: String,
    #[serde(default)]
    pub args: Vec<ContractArg>,
    /// Worked examples, rendered under the command's help.
    ///
    /// Not optional in practice: a guard asserts every routed command carries
    /// at least one, because a command surface an agent cannot learn from
    /// `--help` is one it will guess at instead.
    #[serde(default, skip_serializing_if = "Vec::is_empty")]
    pub examples: Vec<ContractExample>,
}

impl ContractCommand {
    /// The block rendered under a command's help: worked examples, then the
    /// flat name the same command answers to.
    pub fn after_help(&self) -> String {
        let mut text = String::new();
        if !self.examples.is_empty() {
            text.push_str("Examples:\n");
            for (index, example) in self.examples.iter().enumerate() {
                if index > 0 {
                    text.push('\n');
                }
                text.push_str(&format!("  {}:\n    {}\n", example.intent, example.command));
            }
            text.push('\n');
        }
        text.push_str(&format!("Wire name: {}", self.wire_name));
        text
    }

    /// Space-joined spelling, e.g. `agents versions list`.
    pub fn spelling(&self) -> String {
        let mut parts = self.path.clone();
        parts.push(self.verb.clone());
        parts.join(" ")
    }

    /// The parser and the help for this command, as both consumers see it.
    ///
    /// `display_name` is the spelling the caller typed, so usage and errors
    /// read back the grammar they used rather than a wire name they did not.
    pub fn clap_command(&self, display_name: &str) -> Command {
        // clap panics on a duplicate argument id, and an argument named `help`
        // would collide with the flag clap adds for itself. Commands come from
        // a catalog this code does not control, so the collision is resolved
        // deliberately: the declared argument wins and that command has no
        // `--help`. A panic inside an agent's shell is not an acceptable
        // answer to an unusual field name.
        let declares_help = self.args.iter().any(|arg| arg.long == "help");

        let mut command = Command::new(display_name.to_string())
            .about(self.description.clone())
            .disable_version_flag(true)
            .disable_help_flag(declares_help)
            // The workspace links clap with its default features for the CLI,
            // and cargo unifies that across the build, so colour is on unless
            // a command says otherwise. Escape bytes are noise in a terminal
            // and cost tokens in a tool result.
            .color(ColorChoice::Never);

        command = command.after_help(self.after_help());

        for arg in &self.args {
            command = command.arg(flag(arg));
            if arg.position.is_some() {
                command = command.arg(positional(arg));
            }
        }
        command
    }
}

/// Suffix that lets a bare-word spelling coexist with the same argument's
/// long flag. Both reach one parameter, and giving both is a conflict clap
/// reports itself rather than a silent winner.
pub const POSITIONAL_SUFFIX: &str = "\u{1}positional";

fn flag(arg: &ContractArg) -> Arg {
    let mut built = Arg::new(arg.field.clone()).long(arg.long.clone());

    // Parameters are named in snake_case because they are generated from Rust
    // types, while the CLI spells them kebab. Both reach the same parameter,
    // so a script written against either keeps working.
    if arg.long != arg.field {
        built = built.alias(arg.field.clone());
    }
    if let Some(short) = arg.short {
        built = built.short(short);
    }
    if let Some(help) = &arg.help {
        built = built.help(help.clone());
    }
    // An argument that also has a bare-word spelling cannot be required as a
    // flag: the positional may be what supplies it.
    built = built.required(arg.required && arg.position.is_none());
    apply_kind(built, arg)
}

fn positional(arg: &ContractArg) -> Arg {
    let built = Arg::new(format!("{}{POSITIONAL_SUFFIX}", arg.field))
        .index(arg.position.unwrap_or(1))
        .value_name(arg.long.to_uppercase().replace('-', "_"))
        .conflicts_with(arg.field.clone())
        .required(false)
        .help(match &arg.help {
            Some(help) => format!("{help} (may also be given as --{})", arg.long),
            None => format!("{} (may also be given as --{})", arg.field, arg.long),
        });
    apply_kind(built, arg)
}

fn apply_kind(built: Arg, arg: &ContractArg) -> Arg {
    match arg.kind {
        ArgKind::Boolean => built
            .num_args(0..=1)
            .default_missing_value("true")
            .value_parser(BoolishValueParser::new()),
        ArgKind::Integer => built.value_parser(clap::value_parser!(i64)),
        ArgKind::Number => built.value_parser(clap::value_parser!(f64)),
        ArgKind::String if !arg.choices.is_empty() => {
            built.value_parser(PossibleValuesParser::new(arg.choices.clone()))
        }
        ArgKind::String | ArgKind::Json => built,
        // Comma-splitting is safe for scalars and wrong for documents, which
        // may carry a comma of their own.
        ArgKind::StringList | ArgKind::IntegerList => {
            built.action(ArgAction::Append).value_delimiter(',')
        }
    }
}

pub mod declare;
pub mod render;
pub mod schema;

pub use declare::{CliArg, CliExample, CliRoute};

/// Read what clap parsed back out as the parameter object a command expects.
///
/// The contract knows what each argument was declared as, so this does not
/// have to guess: an integer flag comes back a JSON number, a list comes back
/// an array, and a document comes back parsed. Arguments the caller did not
/// give are left out entirely, because defaults belong to the command and
/// sending a parser's view of them would overwrite a real default with a guess.
pub fn params_from(command: &ContractCommand, matches: &clap::ArgMatches) -> serde_json::Value {
    let mut object = serde_json::Map::new();

    for arg in &command.args {
        // A bare-word spelling carries the same parameter under a distinct
        // argument id; whichever the caller used, one value lands under the
        // field's real name.
        let ids = [
            arg.field.clone(),
            format!("{}{POSITIONAL_SUFFIX}", arg.field),
        ];
        for id in ids {
            if let Some(value) = read(matches, &id, arg.kind) {
                object.insert(arg.field.clone(), value);
                break;
            }
        }
    }

    serde_json::Value::Object(object)
}

fn read(matches: &clap::ArgMatches, id: &str, kind: ArgKind) -> Option<serde_json::Value> {
    use serde_json::Value;

    // `try_get_one` rather than `get_one`: an id the command does not declare
    // makes clap panic, and a positional id only exists when one was declared.
    if !matches!(
        matches.try_get_one::<String>(id).err(),
        None | Some(clap::parser::MatchesError::Downcast { .. })
    ) {
        return None;
    }
    if !matches!(
        matches.value_source(id),
        Some(clap::parser::ValueSource::CommandLine)
    ) {
        return None;
    }

    match kind {
        ArgKind::Boolean => matches.get_one::<bool>(id).copied().map(Value::Bool),
        ArgKind::Integer => matches
            .get_one::<i64>(id)
            .copied()
            .map(|value| Value::Number(value.into())),
        ArgKind::Number => matches
            .get_one::<f64>(id)
            .copied()
            .and_then(|value| serde_json::Number::from_f64(value).map(Value::Number)),
        ArgKind::String => matches.get_one::<String>(id).cloned().map(Value::String),
        ArgKind::Json => matches.get_one::<String>(id).map(|text| json_or_text(text)),
        ArgKind::StringList => Some(Value::Array(
            matches
                .get_many::<String>(id)?
                .cloned()
                .map(Value::String)
                .collect(),
        )),
        ArgKind::IntegerList => Some(Value::Array(
            matches
                .get_many::<String>(id)?
                .map(|text| json_or_text(text))
                .collect(),
        )),
    }
}

/// Parse a value that should be JSON, keeping the raw text when it is not.
///
/// Passing the text on is deliberate: the command validates against its own
/// schema and will say what was wrong with it, which is a better error than one
/// invented here with no knowledge of the target type.
fn json_or_text(text: &str) -> serde_json::Value {
    serde_json::from_str(text).unwrap_or_else(|_| serde_json::Value::String(text.to_string()))
}

/// Every command the control plane routes, as a checked-in artifact.
///
/// The contracts are derived from the command types in `everruns-server`, which
/// the CLI cannot link: it would pull a database, a scheduler and a web server
/// into a binary that talks HTTP. So generation happens where the commands are
/// and the result travels as data, with a guard in the server asserting that
/// this file still matches inventory.
///
/// Fetching the catalog at runtime instead would make `everruns --help` need a
/// network round trip and a credential, which is the wrong trade for a CLI.
pub fn commands() -> &'static [ContractCommand] {
    static COMMANDS: std::sync::OnceLock<Vec<ContractCommand>> = std::sync::OnceLock::new();
    COMMANDS.get_or_init(|| {
        // The artifact is compiled in, so a parse failure is a broken build
        // rather than a runtime condition: there is no catalog to fall back to
        // and an empty one would silently serve a CLI with no commands. The
        // parse error travels with the message, because "it is stale" alone
        // does not say which field moved.
        match serde_json::from_str(include_str!("../commands.json")) {
            Ok(commands) => commands,
            Err(error) => panic!(
                "commands.json is generated and checked in; a parse failure means it is stale: {error}"
            ),
        }
    })
}

#[cfg(test)]
mod round_trip {
    use super::*;
    use declare::{CliArg, CliExample, CliRoute};
    use serde_json::json;

    const ROUTE: CliRoute = CliRoute::new(&["widgets"], "update")
        .with_args(&[
            CliArg::new("id").at(1),
            CliArg::new("harness_name").short('H').long("harness"),
            CliArg::new("tag").short('t'),
        ])
        .with_examples(&[CliExample::new(
            "Rename a widget",
            "everruns widgets update w_1 --name blue",
        )]);

    fn contract() -> ContractCommand {
        schema::contract_for(
            "update_widget",
            "Update a widget.",
            "PATCH",
            "/v1/widgets/{id}",
            &ROUTE,
            &json!({
                "type": "object",
                "properties": {
                    "id": { "type": "string" },
                    "name": { "type": "string" },
                    "harness_name": { "type": "string" },
                    "tag": { "type": "array", "items": { "type": "string" } },
                    "limit": { "type": "integer" },
                    "archived": { "type": "boolean" },
                    "metadata": { "type": "object" }
                },
                "required": ["id"]
            }),
        )
    }

    fn parse(line: &str) -> serde_json::Value {
        let contract = contract();
        let parser = contract.clap_command("everruns widgets update");
        let argv = std::iter::once("everruns widgets update".to_string())
            .chain(line.split_whitespace().map(ToOwned::to_owned));
        let matches = parser
            .try_get_matches_from(argv)
            .unwrap_or_else(|error| panic!("{line}: {error}"));
        params_from(&contract, &matches)
    }

    /// The two halves of the contract agree: what the parser accepts comes
    /// back as the type the schema declared.
    #[test]
    fn values_come_back_as_the_types_the_schema_declared() {
        let params = parse("w_1 --limit 5 --archived --tag a,b --metadata {\"k\":1}");
        assert_eq!(params["id"], "w_1");
        assert_eq!(params["limit"], 5);
        assert_eq!(params["archived"], true);
        assert_eq!(params["tag"], json!(["a", "b"]));
        assert_eq!(params["metadata"], json!({ "k": 1 }));
    }

    /// A short option and a renamed long reach the parameter's real name, so
    /// presentation never leaks into what the command receives.
    #[test]
    fn presentation_does_not_reach_the_command() {
        for line in ["w_1 -H generic", "w_1 --harness generic"] {
            assert_eq!(parse(line)["harness_name"], "generic", "{line}");
        }
    }

    /// The parameter's own snake_case name keeps working, so a script written
    /// against the flat command surface does not break.
    #[test]
    fn the_schemas_own_spelling_is_still_accepted() {
        assert_eq!(
            parse("w_1 --harness_name generic")["harness_name"],
            "generic"
        );
    }

    #[test]
    fn a_bare_word_and_its_flag_reach_the_same_parameter() {
        assert_eq!(parse("w_1")["id"], "w_1");
        assert_eq!(parse("--id w_1")["id"], "w_1");
    }

    /// The schema decides, so nothing guesses: a parser sniffing at `1.20`
    /// would make it 1.2 before the command ever saw it.
    #[test]
    fn a_version_like_value_stays_a_string() {
        assert_eq!(parse("w_1 --name 1.20")["name"], "1.20");
    }

    #[test]
    fn an_untouched_flag_is_not_sent() {
        let params = parse("w_1");
        assert_eq!(params, json!({ "id": "w_1" }));
    }

    /// Worked examples reach the help block in yolop's shape: the intent, then
    /// the command line under it.
    #[test]
    fn help_carries_the_worked_examples_and_the_wire_name() {
        let help = contract()
            .clap_command("everruns widgets update")
            .render_long_help()
            .to_string();
        assert!(help.contains("Rename a widget:"), "{help}");
        assert!(
            help.contains("everruns widgets update w_1 --name blue"),
            "{help}"
        );
        assert!(help.contains("Wire name: update_widget"), "{help}");
        assert!(!help.contains('\u{1b}'), "escape bytes in help: {help:?}");
    }
}