headwater-cli 0.2.0

// SPDX-License-Identifier: Apache-2.0
//! What `headwater init` writes, byte for byte.
//!
//! # The defect this target exists for
//!
//! `headwater init` writes two files, and until this target no test of this
//! workspace read one byte of either. One `match` arm of the verb emits two
//! messages under one condition: the comment it writes above `version: 0.0.0`,
//! and the line it prints in its report. #276 found those two drifted apart —
//! the printed one naming two routes and the written one naming a route an
//! adopter cannot take — because the printed one was held and the written one
//! was held by nothing. That arm is still one arm.
//!
//! `.claude/tutorial/drive.py` does hold part of it: three substrings of the
//! declaration, the literal `  version: 0.0.0` line, and the fact that the
//! overlay ends `add: {}`. That guard is real and it sits in the wrong place
//! twice over. It is six claims rather than the file, and its failure message
//! is about a sixteen-step tutorial rather than about `init`. Its own comment
//! named #174 as the missing test's home, and #174 is closed.
//!
//! This target is a characterization of the verb rather than a statement of
//! what the verb should write. It passed on the day it was written, against an
//! unmodified `init`. Its value is that the bytes now have a reader.
//!
//! # Why the two arms are asserted differently
//!
//! The blank-tree arm is asserted as bytes, because every byte of it is a
//! literal in the verb.
//!
//! The package-present arm embeds the version the package declares, so this
//! target reads that version out of the manifest it copied rather than writing
//! it here. A literal would be the defect #427 already caused once: a bump to
//! 4.0.0 moved six mentions in the tutorial, left one behind, and failed every
//! step from 5 to 16 of a tutorial that was right.
//!
//! # What the last line is for
//!
//! `add: {}` is the last line of the overlay, and `.claude/tutorial/drive.py`
//! splices the reader's edit in at exactly that offset. Holding it here makes
//! a break point at `init`, which is where it belongs.
//!
//! # One oddity this target pins rather than repairs
//!
//! The declaration carries one comment at column zero — `# A bundle is an
//! optional part of the package` — where every comment around it carries two
//! spaces. A `\` line continuation in the verb's format string eats the
//! leading whitespace of the line that follows it. YAML reads a comment
//! wherever it sits, so nothing downstream is wrong, and the adopter commits
//! the file all the same. It is pinned here rather than repaired, because this
//! target exists to record what the verb writes today.

use std::path::{Path, PathBuf};
use std::process::Command;

/// The repository this test tree sits in.
fn repository() -> PathBuf {
    Path::new(env!("CARGO_MANIFEST_DIR"))
        .join("../../..")
        .canonicalize()
        .expect("the repository root resolves")
}

/// Everything the declaration carries before the version block.
const DECLARATION_HEAD: &str = r"# The consumer declaration, written by `headwater init`. It says two things,
# and they are different questions: what schema this repository takes, and what
# tree it walks.
#
# `headwater taxonomy resolve` reads this and writes .headwater/taxonomy.lock. Everything after that
# reads the lock and never these sources.

taxonomy:
  package: headwater/standard
";

/// The version block of the arm that found no package, which is an interview
/// stub, nine lines of comment and one commented field.
///
/// This constant is a copy of a string in the verb, and a copy checked against
/// nothing but itself is what #641 cost. The last case in this file runs the
/// route these bytes name, so the bytes have a reader that is not another copy
/// of them.
const NO_PACKAGE_VERSION: &str = r"  # INTERVIEW: no package of this name is under `.headwater/packages/`. Two routes
  # reach a lock, and each one needs a different field below.
  # Copy a package directory into `.headwater/packages/`, and pin `version` at
  # the version that package declares. Or run
  # `headwater taxonomy vendor <dir-or-location>` on a published artifact,
  # unpacked or at the `https://` location of its zip: that verb reads `digest`
  # and refuses until it holds the digest the publisher printed, and
  # `headwater taxonomy resolve` reads `version` after it, so the vendor route
  # needs the digest first and the version as well.
  # digest: sha256:<the digest the publisher printed>
  version: 0.0.0
";

/// Everything the declaration carries after the version block.
///
/// Its first line is the comment at column zero that the module header names.
const DECLARATION_TAIL: &str = r"# A bundle is an optional part of the package, and a selection is add-only.
  # INTERVIEW: which traditions does this corpus already follow?
  bundles: []
  overlay: .headwater/overlay.yml

corpus:
  # Proposed from this tree: the directory holding the most Markdown.
  root: docs
  # An exclusion states a reason. A pattern with none is a silent pass with a
  # configuration file in front of it, so the reason is not optional.
  # exclude:
  #   - path: docs/vendor/**
  #     reason: vendored copies of documents another team owns
";

/// The whole overlay. It is one arm, because `init` writes the same overlay
/// whether a package is on the tree or not.
const OVERLAY: &str = r#"# The adopter overlay, written by `headwater init`. It is an overlay and never a
# resolved taxonomy, so nothing here can weaken the package it sits on: a
# bundle selection is add-only, and an add-only overlay carries no operation
# that removes a base rule.
#
# Every block below is a question this engine cannot answer from a tree. It is
# prose about what this corpus is for, and a corpus does not state it.
#
# INTERVIEW 1 --- what does each purpose answer?
#
# A task is matched against declared purposes before it is matched against any
# text, and it is matched on the `answers` phrases first. Two purposes whose
# phrases share every term separate nothing, and every task then matches both
# equally. Read `headwater/standard`'s purposes, and add the phrases a person here would
# actually type.
#
#   add:
#     purposes.rationale.answers: ["why is it this way", "what was rejected"]
#
# INTERVIEW 2 --- what identifies a document, and what does the prefix mean?
#
# A relation names its target by identifier. A corpus whose documents carry none
# has no edges, and no check about an edge can say anything about it.
#
# `add` states a value the package leaves unstated, and `override` replaces one
# the package already states, so the operation follows the package rather than
# the taste of the writer. `headwater/standard` declares `decision_id` with no namespace
# and gives `decision` that scheme, so the namespace below is an `add` on a leaf
# the package leaves empty, and the kind below is an `override` because `add`
# over a value the package already states is refused. Replace ACME with the
# prefix this corpus uses.
#
#   add:
#     identifier_schemes.doc_id: {pattern: "{namespace}-DOC-{slug}", namespace: ACME, allocation: minted-once}
#     identifier_schemes.decision_id.namespace: ACME
#   override:
#     kinds.decision.identifier: {scheme: doc_id}
#
# INTERVIEW 3 --- what does this corpus already write?
#
# Run `headwater infer` once this file resolves. It reports the files that
# classify as nothing, which is the half a payload cannot carry, and the
# documents that state no summary, which nothing will route to.

add: {}
"#;

/// A scratch repository, and what one run of `init` leaves in it.
struct Root {
    at: PathBuf,
}

impl Root {
    /// A tree holding one Markdown file under `docs/`, which is the least that
    /// reaches the write path: `busiest_directory` proposes a corpus root from
    /// the directory holding the most Markdown, and a tree with none is
    /// refused.
    ///
    /// `label` names the case rather than the process, for the reason
    /// `wiring.rs` records beside its own helper. Cargo runs the cases of one
    /// target as threads of one process, so a directory keyed on the process
    /// alone is a directory one case removes while another is reading it.
    fn over(label: &str) -> Root {
        let at =
            std::env::temp_dir().join(format!("headwater-cli-init-{}-{label}", std::process::id()));
        let _ = std::fs::remove_dir_all(&at);
        std::fs::create_dir_all(at.join("docs")).expect("the corpus directory is there");
        std::fs::write(at.join("docs/one.md"), "# a document\n").expect("the document writes");
        Root { at }
    }

    /// The same tree, plus the manifest of the package this repository
    /// maintains.
    ///
    /// The manifest alone is the whole of the package-present arm, because
    /// `find_version` reads `package.yml` and opens nothing else. Copying the
    /// real one rather than writing a stand-in is what couples this target to
    /// the version the repository actually ships.
    fn with_package(label: &str) -> Root {
        let root = Root::over(label);
        let directory = root.at.join(".headwater/packages/headwater-standard");
        std::fs::create_dir_all(&directory).expect("the package directory is there");
        std::fs::copy(
            repository().join(".headwater/packages/headwater-standard/package.yml"),
            directory.join("package.yml"),
        )
        .expect("the manifest copies");
        root
    }

    /// One run of the verb over this root.
    ///
    /// The exit status is asserted here rather than returned, because every
    /// case below reads a file the verb writes and a refusal writes neither.
    fn init(&self) {
        let output = Command::new(env!("CARGO_BIN_EXE_headwater"))
            .args(["init", "--root"])
            .arg(&self.at)
            .output()
            .expect("the binary runs");
        assert_eq!(
            output.status.code(),
            Some(0),
            "`headwater init` writes both files:\n{}",
            String::from_utf8_lossy(&output.stderr)
        );
    }

    fn read(&self, relative: &str) -> String {
        std::fs::read_to_string(self.at.join(relative)).expect("the written file reads")
    }

    /// The version the copied manifest declares, read rather than written.
    ///
    /// The assertion on the count is the point of the helper. A manifest that
    /// stops declaring a version at the top level, or that declares two, fails
    /// here and names what it found, rather than silently answering with the
    /// wrong line.
    fn declared_version(&self) -> String {
        declared_version_at(
            &self
                .at
                .join(".headwater/packages/headwater-standard/package.yml"),
        )
    }

    /// A scratch directory beside this root, for something that is not part of
    /// the tree `init` reads.
    ///
    /// A published artifact under the root would join the tree that
    /// `busiest_directory` walks, so it goes outside rather than inside.
    fn beside(&self, label: &str) -> PathBuf {
        let at = self.at.with_file_name(format!(
            "{}-{label}",
            self.at
                .file_name()
                .expect("the scratch root is named")
                .to_string_lossy()
        ));
        let _ = std::fs::remove_dir_all(&at);
        std::fs::create_dir_all(&at).expect("the scratch directory is made");
        at
    }

    fn write(&self, relative: &str, body: &str) {
        std::fs::write(self.at.join(relative), body).expect("the file writes");
    }

    /// One run of the built binary over this root, with an optional path
    /// argument, returning the status and standard error.
    ///
    /// The two streams are kept apart, because a verb of this engine writes its
    /// report to one and its account of a refusal to the other.
    fn run(&self, verb: &[&str], argument: Option<&Path>) -> (Option<i32>, String) {
        let mut command = Command::new(env!("CARGO_BIN_EXE_headwater"));
        command.args(verb);
        if let Some(path) = argument {
            command.arg(path);
        }
        let output = command
            .arg("--root")
            .arg(&self.at)
            .output()
            .expect("the binary runs");
        (
            output.status.code(),
            String::from_utf8_lossy(&output.stderr).into_owned(),
        )
    }
}

/// The version a package manifest declares at the top level, read rather than
/// written.
///
/// The assertion on the count is the point of the helper. A manifest that stops
/// declaring a version at the top level, or that declares two, fails here and
/// names what it found, rather than silently answering with the wrong line.
fn declared_version_at(manifest: &Path) -> String {
    let body = std::fs::read_to_string(manifest)
        .unwrap_or_else(|error| panic!("{} reads: {error}", manifest.display()));
    let lines: Vec<&str> = body
        .lines()
        .filter(|line| line.starts_with("version:"))
        .collect();
    assert_eq!(
        lines.len(),
        1,
        "{} declares one version at the top level, and it declares {}",
        manifest.display(),
        lines.len()
    );
    lines[0].trim_start_matches("version:").trim().to_string()
}

/// The version this repository's maintained source of `headwater/standard`
/// declares.
fn maintained_version() -> String {
    declared_version_at(&repository().join("taxonomy-source/headwater-standard/package.yml"))
}

/// `taxonomy publish --from` over this repository's maintained source, giving
/// back the digest the report printed.
///
/// The digest is read out of the report rather than written here, so a change to
/// the package moves this case with it. `publish.rs` holds what the verb writes
/// to disk; this reads the one line the report tells a consumer to pin, and it
/// names `taxonomy-source/headwater-standard/` for the reason that target
/// states: it is the maintained source, and `.headwater/packages/headwater-standard/` is a
/// vendored artifact that `publish` refuses.
fn publish_maintained_source_into(out: &Path) -> String {
    let output = Command::new(env!("CARGO_BIN_EXE_headwater"))
        .arg("taxonomy")
        .arg("publish")
        .arg("--from")
        .arg(repository().join("taxonomy-source/headwater-standard"))
        .arg("--out")
        .arg(out)
        .arg("--root")
        .arg(repository())
        .output()
        .expect("the binary runs");
    assert_eq!(
        output.status.code(),
        Some(0),
        "the artifact publishes:\n{}",
        String::from_utf8_lossy(&output.stderr)
    );
    let report = String::from_utf8_lossy(&output.stdout).into_owned();
    let stated: Vec<&str> = report
        .lines()
        .filter_map(|line| line.trim().strip_prefix("digest "))
        .collect();
    assert_eq!(
        stated.len(),
        1,
        "the publish report states one digest, and it states {}:\n{report}",
        stated.len()
    );
    stated[0].to_string()
}

/// The declaration of a tree with no package under `.headwater/packages/`.
///
/// This is the first-run state that spec 7 calls the surface `init` is for,
/// and it is the state the tutorial runs its step 2 in. Every byte of it is a
/// literal in the verb, so every byte of it is asserted.
#[test]
fn the_declaration_of_a_tree_with_no_package_is_written_byte_for_byte() {
    let root = Root::over("declaration-no-package");
    root.init();
    let expected = format!("{DECLARATION_HEAD}{NO_PACKAGE_VERSION}{DECLARATION_TAIL}");
    assert_eq!(
        root.read(".headwater/taxonomy.yml"),
        expected,
        "the declaration `headwater init` writes on a blank tree"
    );
}

/// The overlay, which is one arm and carries no package-dependent byte.
#[test]
fn the_overlay_is_written_byte_for_byte() {
    let root = Root::over("overlay");
    root.init();
    assert_eq!(
        root.read(".headwater/overlay.yml"),
        OVERLAY,
        "the overlay `headwater init` writes"
    );
}

/// The declaration of a tree that carries the package, which pins the version
/// the package declares.
///
/// The version is read out of the manifest this case copied. A literal here
/// would go stale on the next bump of the package, which is what #427 did to
/// the tutorial: six mentions moved, one stayed, and every step from 5 to 16
/// failed on a document that was right.
#[test]
fn the_declaration_of_a_tree_with_a_package_pins_the_version_that_package_declares() {
    let root = Root::with_package("declaration-with-package");
    let version = root.declared_version();
    root.init();
    let expected = format!("{DECLARATION_HEAD}  version: {version}\n{DECLARATION_TAIL}");
    assert_eq!(
        root.read(".headwater/taxonomy.yml"),
        expected,
        "the declaration `headwater init` writes over a package it found"
    );
    assert!(
        !expected.contains("0.0.0"),
        "a package on the tree replaces the interview stub rather than joining it"
    );
}

/// `add: {}` is the last line of the overlay.
///
/// `.claude/tutorial/drive.py` asserts the same thing and then splices the
/// reader's edit in at that offset, so anything appended after it breaks a
/// driver assertion rather than an output block, and re-recording the block
/// does not repair it. Held here as well, so that a break points at the verb.
#[test]
fn the_last_line_of_the_overlay_is_the_line_the_tutorial_replaces() {
    let root = Root::over("overlay-last-line");
    root.init();
    let overlay = root.read(".headwater/overlay.yml");
    assert!(
        overlay.trim_end_matches('\n').ends_with("add: {}"),
        "the last line of the overlay is `add: {{}}`, and the tutorial replaces it in place:\n{}",
        overlay
            .lines()
            .rev()
            .take(3)
            .collect::<Vec<&str>>()
            .join("\n")
    );
}

/// The route the declaration names, run rather than read.
///
/// # Why this case exists
///
/// Every other case in this target asserts that the declaration *says*
/// something. None of them runs a command it names, so the comment `init`
/// writes was a claim about this engine sitting in a string literal, checked
/// only against a copy of itself in this file. [#641] is what that costs: the
/// comment stated one requirement for two routes that need different fields,
/// an adopter who did exactly what it said met `nothing pins this artifact`,
/// and both copies agreed with each other the whole time.
///
/// `.claude/tutorial/fixtures.sh` does not cover it either. The tutorial takes
/// the copy route, so `taxonomy vendor` is outside the population that suite
/// runs.
///
/// So this case reads the instruction out of the file the verb just wrote,
/// performs it, and runs the command the file names. It publishes a real
/// artifact from this repository's own maintained source rather than a
/// synthetic one, for the reason `publish.rs` states beside the same source:
/// the manifest of a small stand-in does not reach the paths a real one does.
///
/// # What it asserts, and in the order an adopter meets it
///
/// The declaration names a `digest` field. `taxonomy vendor` accepts the
/// artifact once that field carries the digest the publisher printed.
/// `taxonomy resolve` then gets past the version, which is the second field
/// the vendor route needs and the one the comment used to name alone.
///
/// `resolve` still refuses after all of that, and that refusal is by design:
/// it is the interview asking this corpus for an identifier namespace, which
/// no engine can answer off a tree. This case asserts the refusal is no longer
/// the version one.
///
/// [#641]: https://github.com/headwater-ai/headwater/issues/641
#[test]
fn the_vendor_route_the_declaration_names_reaches_a_resolved_version() {
    let root = a_root_the_vendor_route_reached("vendor-route");

    let (_, stderr) = root.run(&["taxonomy", "resolve"], None);
    assert!(
        !stderr.contains("this takes headwater/standard"),
        "`headwater taxonomy resolve` is past the version the vendor route also needs:\n{stderr}"
    );
}

/// A root that `init` wrote and that the vendor route the declaration names has
/// carried as far as a package on disk at the pinned version.
///
/// This is the setup of the two cases below it, extracted rather than typed
/// twice. Every edit in it is read out of a file the verb wrote, so a verb that
/// stops writing one of those lines fails here.
fn a_root_the_vendor_route_reached(label: &str) -> Root {
    let root = Root::over(label);
    let artifact = root.beside("artifact");
    let digest = publish_maintained_source_into(&artifact);
    root.init();

    // The edit the comment instructs, taken from the file rather than written
    // here: the commented `digest` line the declaration carries is the only
    // hint an adopter has that the field exists, so a declaration that stops
    // carrying it fails here rather than one command later in their tree.
    let declaration = root.read(".headwater/taxonomy.yml");
    let commented = declaration
        .lines()
        .find(|line| line.trim_start().starts_with("# digest:"))
        .unwrap_or_else(|| {
            panic!(
                "the declaration names the field `taxonomy vendor` reads, and it names none of \
                 these:\n{declaration}"
            )
        });
    let version = maintained_version();
    let pinned = declaration
        .replace(commented, &format!("  digest: {digest}"))
        .replace("  version: 0.0.0\n", &format!("  version: {version}\n"));
    assert!(
        pinned.contains(&format!("  digest: {digest}\n")),
        "the commented line is replaced by the pin:\n{pinned}"
    );
    root.write(".headwater/taxonomy.yml", &pinned);

    let (code, stderr) = root.run(&["taxonomy", "vendor"], Some(&artifact));
    assert_eq!(
        code,
        Some(0),
        "`headwater taxonomy vendor` accepts the artifact the declaration pins:\n{stderr}"
    );
    assert_eq!(
        declared_version_at(
            &root
                .at
                .join(".headwater/packages/headwater-standard/package.yml")
        ),
        version,
        "the vendored package is the one the declaration pins"
    );
    root
}

/// The example the overlay prints under `INTERVIEW 2`, lifted out of the file
/// `init` wrote and given back with the comment prefix and the common indent
/// removed.
///
/// # Why it is read rather than typed
///
/// The case below runs these lines. A case that retyped them would pass forever
/// whatever the template said, which is the defect `OVERLAY` above has on its
/// own: a string literal held against a copy of itself. Reading them here makes
/// the template the thing under test.
///
/// The example lines are the ones this block indents past its prose: a comment
/// line of the block carries one space after the `#`, and an example line
/// carries three or more. The panic is the second half of the mechanism —
/// a template that stopped printing an example would otherwise hand back an
/// empty patch, and the case would then be asserting something else.
fn the_interview_2_example(overlay: &str) -> String {
    let block: Vec<&str> = overlay
        .lines()
        .skip_while(|line| !line.starts_with("# INTERVIEW 2"))
        .skip(1)
        .take_while(|line| !line.starts_with("# INTERVIEW"))
        .collect();
    let example: Vec<&str> = block
        .iter()
        .filter_map(|line| line.strip_prefix('#'))
        .filter(|rest| rest.starts_with("   "))
        .collect();
    assert!(
        !example.is_empty(),
        "the overlay prints an example under `INTERVIEW 2`, and it prints none of these:\n{overlay}"
    );
    let indent = example
        .iter()
        .map(|line| line.len() - line.trim_start().len())
        .min()
        .expect("the example is not empty");
    example
        .iter()
        .map(|line| format!("{}\n", &line[indent..]))
        .collect()
}

/// The example the overlay hands an adopter resolves.
///
/// # The defect this case exists for
///
/// [#659]. `INTERVIEW 2` asks the corpus what identifies a document, and the
/// example under it was the only answer an adopter reading that file ever saw.
/// It answered nothing twice over: it declared a scheme of its own and never
/// the namespace that `headwater/standard` leaves to the corpus, so `resolve`
/// refused with `carries no namespace after resolution`; and it stated
/// `kinds.<kind>.identifier` under `add` over a kind the package already gives
/// an identifier, which `resolve` refuses on its own terms. Neither refusal
/// moves the other, so the example had to be repaired in both places at once.
///
/// The case that precedes this one is [#641]'s, and it stops one refusal short:
/// it asserts `resolve` is past the version and lets the namespace refusal
/// stand, because that refusal is by design. This case is the continuation. It
/// performs the overlay's own instruction and asserts `resolve` writes a lock.
///
/// # Why it extracts rather than retypes
///
/// See `the_interview_2_example`. Reverting the template to the example this
/// case was written against fails here with the refusal above, which is the
/// discriminator a retyped copy would not have.
///
/// [#641]: https://github.com/headwater-ai/headwater/issues/641
/// [#659]: https://github.com/headwater-ai/headwater/issues/659
#[test]
fn the_overlay_example_the_interview_prints_reaches_a_lock() {
    let root = a_root_the_vendor_route_reached("interview-example");

    let overlay = root.read(".headwater/overlay.yml");
    assert!(
        overlay.trim_end_matches('\n').ends_with("add: {}"),
        "the overlay ends with the line the example replaces:\n{overlay}"
    );
    let patched = format!(
        "{}{}",
        overlay.trim_end_matches('\n').trim_end_matches("add: {}"),
        the_interview_2_example(&overlay)
    );
    root.write(".headwater/overlay.yml", &patched);

    let (code, stderr) = root.run(&["taxonomy", "resolve"], None);
    assert_eq!(
        code,
        Some(0),
        "the example `INTERVIEW 2` prints resolves:\n{stderr}\nthe overlay it was run \
         against:\n{patched}"
    );
}

/// The argument `taxonomy vendor` takes, as the interface contract states it.
///
/// `docs/interfaces/headwater-taxonomy.md` is the contract for the verb, so the
/// placeholder `init` prints is held to that row rather than to a copy of it in
/// this file. A contract that renames the argument moves this case with it.
fn the_vendor_argument_the_contract_states() -> String {
    let contract =
        std::fs::read_to_string(repository().join("docs/interfaces/headwater-taxonomy.md"))
            .expect("the interface contract reads");
    let rows: Vec<String> = contract
        .lines()
        .filter_map(|line| line.strip_prefix("| `vendor <"))
        .filter_map(|rest| {
            rest.split_once('>')
                .map(|(argument, _)| argument.to_string())
        })
        .collect();
    assert_eq!(
        rows.len(),
        1,
        "the contract states one `vendor` row, and it states {}",
        rows.len()
    );
    rows[0].clone()
}

/// Every argument placeholder that follows `headwater taxonomy vendor` in `text`.
fn vendor_placeholders(text: &str) -> Vec<String> {
    let squeezed = text
        .lines()
        .map(|line| line.trim_start().trim_start_matches('#').trim())
        .collect::<Vec<_>>()
        .join(" ");
    squeezed
        .match_indices("headwater taxonomy vendor <")
        .filter_map(|(at, marker)| {
            squeezed[at + marker.len()..]
                .split_once('>')
                .map(|(argument, _)| argument.to_string())
        })
        .collect()
}

/// Pack a published artifact directory into the zip `release-taxonomy.yml`
/// uploads: every member at the root of the archive, deflated.
///
/// A copy of the helper of the same name in `publish.rs`. Two targets of one
/// crate share no module unless one is written for them, and `tests/common`
/// carries nothing about a published artifact.
#[cfg(feature = "fetch")]
fn zipped(artifact: &Path) -> Vec<u8> {
    use std::io::Write;
    let mut members = Vec::new();
    let mut pending = vec![artifact.to_path_buf()];
    while let Some(dir) = pending.pop() {
        for entry in std::fs::read_dir(&dir).expect("the artifact directory reads") {
            let path = entry.expect("the entry reads").path();
            if path.is_dir() {
                pending.push(path);
            } else {
                members.push(path);
            }
        }
    }
    members.sort();
    let mut writer = zip::ZipWriter::new(std::io::Cursor::new(Vec::new()));
    let options = zip::write::SimpleFileOptions::default()
        .compression_method(zip::CompressionMethod::Deflated);
    for path in members {
        let name = path
            .strip_prefix(artifact)
            .expect("under the artifact")
            .to_str()
            .expect("the path is UTF-8")
            .replace('\\', "/");
        writer.start_file(name, options).expect("the member starts");
        writer
            .write_all(&std::fs::read(&path).expect("the member reads"))
            .expect("the member writes");
    }
    writer.finish().expect("the archive closes").into_inner()
}

/// Serve `body` at `/<name>` on 127.0.0.1 for as long as the test process
/// lives, and give back the location. `headwater-fetch` takes plain `http`
/// to a loopback host alone, so the suite reaches no other host.
#[cfg(feature = "fetch")]
fn serve(name: &str, body: Vec<u8>) -> String {
    use std::io::{Read, Write};
    let listener = std::net::TcpListener::bind("127.0.0.1:0").expect("a loopback port binds");
    let location = format!(
        "http://{}/{name}",
        listener.local_addr().expect("the port reads")
    );
    let wanted = format!("/{name}");
    std::thread::spawn(move || {
        for stream in listener.incoming() {
            let Ok(mut stream) = stream else { continue };
            let mut request = [0_u8; 4096];
            let read = stream.read(&mut request).unwrap_or(0);
            let line = String::from_utf8_lossy(&request[..read]).to_string();
            let found = line.split_whitespace().nth(1) == Some(wanted.as_str());
            let (head, payload): (String, &[u8]) = if found {
                (
                    format!(
                        "HTTP/1.1 200 OK\r\nContent-Length: {}\r\nConnection: close\r\n\r\n",
                        body.len()
                    ),
                    &body,
                )
            } else {
                (
                    "HTTP/1.1 404 Not Found\r\nContent-Length: 0\r\nConnection: close\r\n\r\n"
                        .to_string(),
                    &[],
                )
            };
            let _ = stream.write_all(head.as_bytes());
            let _ = stream.write_all(payload);
        }
    });
    location
}

/// The vendor route `init` names takes the location a release publishes.
///
/// # Why this case exists
///
/// `HW-OBL-0085` recorded that this engine fetched no package, and `init`
/// said so in both messages of its no-package arm. [#959] gave
/// `taxonomy vendor` a location, so that sentence became false and the remedy
/// named `<dir>` alone. An adopter with no copy of the artifact on disk read
/// that they had to fetch and unpack it by other means. This is the #271 and
/// [#641] failure again: the first verb an adopter runs states a remedy that
/// does not match the binary in front of them.
///
/// # What it asserts
///
/// Both messages name the argument the interface contract states for the
/// verb. The case then takes that route as a reader would. It pins the digest
/// in the field the declaration names, and it vendors from a zip served on
/// 127.0.0.1 in the place of the placeholder. `taxonomy resolve` then gets
/// past the version, as the case above asserts for the directory form.
///
/// [#641]: https://github.com/headwater-ai/headwater/issues/641
/// [#959]: https://github.com/headwater-ai/headwater/issues/959
#[cfg(feature = "fetch")]
#[test]
fn the_vendor_route_init_names_takes_the_location_a_release_publishes() {
    let root = Root::over("vendor-location");
    let artifact = root.beside("artifact");
    let digest = publish_maintained_source_into(&artifact);

    let output = Command::new(env!("CARGO_BIN_EXE_headwater"))
        .args(["init", "--root"])
        .arg(&root.at)
        .output()
        .expect("the binary runs");
    assert_eq!(
        output.status.code(),
        Some(0),
        "`headwater init` writes both files"
    );
    let report = String::from_utf8_lossy(&output.stdout).into_owned();
    let declaration = root.read(".headwater/taxonomy.yml");

    let argument = the_vendor_argument_the_contract_states();
    for (name, text) in [
        ("the printed report", &report),
        ("the declaration", &declaration),
    ] {
        assert_eq!(
            vendor_placeholders(text),
            vec![argument.clone()],
            "{name} names `headwater taxonomy vendor <{argument}>`, the argument the contract \
             states:\n{text}"
        );
        assert!(
            !text.contains("fetches one"),
            "{name} no longer says that nothing fetches a package:\n{text}"
        );
    }

    let version = maintained_version();
    let commented = declaration
        .lines()
        .find(|line| line.trim_start().starts_with("# digest:"))
        .expect("the declaration names the field `taxonomy vendor` reads");
    let pinned = declaration
        .replace(commented, &format!("  digest: {digest}"))
        .replace("  version: 0.0.0\n", &format!("  version: {version}\n"));
    root.write(".headwater/taxonomy.yml", &pinned);

    let location = serve(
        &format!("headwater-standard-{version}.zip"),
        zipped(&artifact),
    );
    let (code, stderr) = root.run(&["taxonomy", "vendor", location.as_str()], None);
    assert_eq!(
        code,
        Some(0),
        "`headwater taxonomy vendor <{argument}>` accepts the location a release \
         publishes:\n{stderr}"
    );
    assert_eq!(
        declared_version_at(
            &root
                .at
                .join(".headwater/packages/headwater-standard/package.yml")
        ),
        version,
        "the fetched package is the one the declaration pins"
    );

    let (_, stderr) = root.run(&["taxonomy", "resolve"], None);
    assert!(
        !stderr.contains("this takes headwater/standard"),
        "`headwater taxonomy resolve` is past the version after a fetch:\n{stderr}"
    );
}