command_idempotent

Run a user-declared formatter/checker in its --check (idempotence) mode once: exit 0 ⇒ the tree is formatter-clean (silent); non-zero ⇒ violation(s). The sibling of generated_file_fresh — that rule diffs a generator's captured stdout against a committed file; this trusts a checker's own --check exit code. alint never runs a mutating formatter and never writes the tree. With files_from (stdout/stderr) the tool's own offender list is parsed into one violation per file (optional files_pattern regex, capture group 1 = path, for tools that wrap the path in a message like cargo fmt's Diff in <path> at line N); without it, one violation for the whole invocation. A non-zero exit is never swallowed into a pass. Single-shot, opt-in. Trust-gated like command (see below): declarable only in your own top-level config.

A completed non-zero checker exit is the configured policy verdict and remains a violation. A spawn or wait failure, or a timeout before the checker exits, produces a non-baselinable evaluation analysis failure instead.

As with generated_file_fresh, the optional workdir (the child's working directory, relative to the lint root) must stay inside the repository: an absolute path or a .. that climbs out is rejected when the config loads, and a workdir that resolves outside the repository through a symlink is refused at run time (reported as a spawn failure) instead of running the command there.

Options

Option	Type	Required	Default	Description
command	list of string	yes		Checker argv (no shell), run in its --check / idempotence mode; exit 0 = clean.
files_from	one of none | stdout | stderr		none	On failure, parse this stream into per-file violations (default: none = one violation for the whole invocation).
files_pattern	string		null	Regex whose capture group 1 is a file path, applied per output line (requires files_from; omit for bare-path listers).
timeout	integer (>= 1)		null	Checker timeout in seconds (default 120). On timeout the child is killed and one non-baselinable evaluation analysis failure is emitted.
workdir	string		null	Checker cwd, relative to the lint root (default: lint root).

Plus the common level, id, and when fields. This rule analyses the whole repository, so it takes no paths or expect_matches. This table is generated from the JSON Schema; option types and defaults are authoritative.

Example

A checker that flags an offending file

The rule fires on this repository:

• src/
• src/main.rs✗

  ✗ error fmt-clean

  src/main.rs: not formatter-clean

src/main.rs

fn main() {}

With this .alint.yml:

version: 1
rules:
  - id: fmt-clean
    kind: command_idempotent
    command: ["sh", "-c", "printf 'src/main.rs\\n'; exit 1"]
    files_from: stdout
    level: error

alint check reports:

--- src/main.rs ----------------------------------------------------------------
  x  error    fmt-clean
              src/main.rs: not formatter-clean

Summary (1 violation):
  x 1 error
  0 passing * 1 failing

A checker that exits clean

This repository is compliant:

• src/
• src/main.rs✓

src/main.rs

fn main() {}

With this .alint.yml:

version: 1
rules:
  - id: fmt-clean
    kind: command_idempotent
    command: ["sh", "-c", "exit 0"]
    level: error

alint check reports:

v All 1 rule(s) passed.