yml671 B

GitHub Actions Composite Action Definition

An action.yml-shaped composite action definition with typed inputs, a declared output bound to a step output, and a branding block. Distinct from a workflow file, and a common blind spot in workflow linters that only understand .github/workflows.

Config testing Config parsing Editor testing

Preview — first 31 linesyml

name: Restore build cache
description: Composite action that restores a build cache and reports whether it hit.
author: Novus Examples

inputs:
  key-prefix:
    description: Prefix for the cache key
    required: false
    default: build
  path:
    description: Directory to cache
    required: true

outputs:
  cache-hit:
    description: "true when the cache was restored"
    value: ${{ steps.probe.outputs.hit }}

runs:
  using: composite
  steps:
    - id: probe
      shell: bash
      run: echo "hit=false" >> "$GITHUB_OUTPUT"
    - shell: bash
      run: echo "restoring ${{ inputs.path }} for ${{ inputs.key-prefix }}"

branding:
  icon: archive
  color: blue

Specifications

System: GitHub Actions
Kind: composite action
Inputs: 2
Outputs: 1
Steps: 2

Testing contract

Expected to pass

Scenario: Parse an action definition rather than a workflow and bind its output to a step id
Expected result: The document is recognised as a composite action, and cache-hit resolves to steps.probe.outputs.hit

What is a .yml file?

YML is an alternate file extension for YAML, a human-readable data-serialization format based on indentation, key-value mappings, and lists. The content and parsing rules are identical to .yaml; only the extension differs. It is widely used for CI and application configuration files.

How to use this file

Use an example YML file to test that config loaders treat .yml and .yaml identically, and to exercise indentation, comment, and multi-document parsing.

How to use this file for testing

“GitHub Actions Composite Action Definition” is a deterministic Novus Examples fixture for Config testing, Config parsing, Editor testing. TOML, INI, YAML, .env, and dotfile configuration samples with nested sections and typed values — for testing config parsers, loaders, and environment tooling.

Documented properties for this file: YML · 671 bytes. Compare results against paired or grouped companions on this page when present (clean↔damaged, searchable↔scanned, or format twins) so scores stay reproducible across runs.

Download the file once, keep the path stable in CI or local scripts, and treat the spec table as the contract: dimensions, seeds, field lists, and roles are intentional. Corrupt or invalid samples are labelled as such — expect parsers to fail loudly rather than silently accept them.

Pipeline and infrastructure fixtures are inert configuration: steps reference fictional images and scripts, and nothing here executes. Run your linter, schema validator, migrator, or policy engine against them, and expect the deprecated-syntax and intentionally invalid variants to be rejected.

Point your config loader at the file and assert it reads the documented sections and typed values, including any deliberately-tricky nesting or comments.

Code examples

import yaml  # pip install pyyaml

with open("composite-action.yml") as f:
    data = yaml.safe_load(f)
print(data)

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