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ci: add prettier workflow #18

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f16b794
ci: add workflow for prettier write
hesreallyhim Jun 9, 2026
30899f1
refactor: extract prettier logic into action file
hesreallyhim Jun 9, 2026
6913286
refactor: least privilege
hesreallyhim Jun 9, 2026
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369 changes: 369 additions & 0 deletions .github/actions/prettier-format/action.yml
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name: Format with Prettier
description: Detects project tooling, runs Prettier, and emits a patch when files change.

inputs:
path:
description: File, directory, or quoted glob to format.
required: false
default: .
package-manager:
description: Package manager to use.
required: false
default: auto
node-version:
description: Node.js version. Use auto to read project metadata.
required: false
default: auto
formatter:
description: How to run Prettier.
required: false
default: prettier
script-name:
description: Optional package.json script to run when formatter is package-script.
required: false
default: ""
working-directory:
description: Directory containing the repository to format.
required: false
default: .

outputs:
changed:
description: Whether Prettier changed the working tree.
value: ${{ steps.diff.outputs.changed }}
patch_path:
description: Path to the generated patch when changed is true.
value: ${{ steps.diff.outputs.patch_path }}

runs:
using: composite
steps:
- name: Detect Node.js version
id: node
shell: bash
env:
INPUT_NODE_VERSION: ${{ inputs.node-version }}
WORKING_DIRECTORY: ${{ inputs.working-directory }}
run: |
set -euo pipefail
cd "$WORKING_DIRECTORY"

node_version="$INPUT_NODE_VERSION"

if [ "$node_version" = "auto" ] || [ -z "$node_version" ]; then
node_version=""

for version_file in .nvmrc .node-version; do
if [ -f "$version_file" ]; then
node_version="$(grep -v '^[[:space:]]*$' "$version_file" | grep -v '^[[:space:]]*#' | head -n 1 | tr -d '[:space:]')"
if [ -n "$node_version" ]; then
echo "Detected Node.js version from $version_file: $node_version"
break
fi
fi
done

if [ -z "$node_version" ] && [ -f .npmrc ]; then
node_version="$(
awk -F= '
/^[[:space:]]*(node-version|node_version|use-node-version)[[:space:]]*=/ {
value=$2
gsub(/^[[:space:]]+|[[:space:]]+$/, "", value)
print value
exit
}
' .npmrc
)"
if [ -n "$node_version" ]; then
echo "Detected Node.js version from .npmrc: $node_version"
fi
fi

if [ -z "$node_version" ] && [ -f package.json ]; then
node_version="$(
node <<'NODE'
const fs = require('node:fs');

try {
const packageJson = JSON.parse(fs.readFileSync('package.json', 'utf8'));
const spec = String(packageJson.engines?.node || '').trim();
const match = spec.match(/(?<!\d)(\d{2,})(?:\.\d+)?(?:\.\d+)?/);
console.log(match ? match[1] : spec);
} catch {
console.log('');
}
NODE
)"
if [ -n "$node_version" ]; then
echo "Detected Node.js version from package.json engines.node: $node_version"
fi
fi

if [ -z "$node_version" ]; then
node_version="24"
echo "Defaulting Node.js version to $node_version"
fi
fi

echo "node_version=$node_version" >> "$GITHUB_OUTPUT"

- name: Set up Node.js
uses: actions/setup-node@48b55a011bda9f5d6aeb4c2d9c7362e8dae4041e # v6.4.0
with:
node-version: ${{ steps.node.outputs.node_version }}
package-manager-cache: false

- name: Select Prettier command
id: prettier
shell: bash
env:
INPUT_FORMATTER: ${{ inputs.formatter }}
INPUT_SCRIPT_NAME: ${{ inputs.script-name }}
INPUT_PATH: ${{ inputs.path }}
WORKING_DIRECTORY: ${{ inputs.working-directory }}
run: |
set -euo pipefail
cd "$WORKING_DIRECTORY"

node <<'NODE' >> "$GITHUB_OUTPUT"
const fs = require('node:fs');

const formatter = process.env.INPUT_FORMATTER || 'auto';
const requestedScript = process.env.INPUT_SCRIPT_NAME || '';
const targetPath = process.env.INPUT_PATH || '.';

if (!['auto', 'prettier', 'package-script'].includes(formatter)) {
console.error(`Invalid formatter: ${formatter}`);
process.exit(1);
}

let packageJson = {};
try {
packageJson = JSON.parse(fs.readFileSync('package.json', 'utf8'));
} catch {}

const scripts = packageJson.scripts || {};
const prettierSpec =
packageJson.devDependencies?.prettier ||
packageJson.dependencies?.prettier ||
packageJson.optionalDependencies?.prettier ||
'';
const prettierPackage = prettierSpec ? `prettier@${prettierSpec}` : 'prettier';

function hasPrettierWrite(command) {
return /\bprettier\b/.test(command) && /(^|\s)--write(\s|$)/.test(command);
}

function isFormattingOnly(command) {
if (!hasPrettierWrite(command)) return false;

if (/[;&|`<>]/.test(command)) return false;

const withoutPrettier = command.replace(/\bprettier\b/g, '').toLowerCase();

return !/\b(eslint|lint-staged|tsc|vitest|jest|mocha|ava|node|npm|pnpm|yarn|bash|sh|biome|rome)\b/.test(withoutPrettier);
}

const preferredNames = [
'format',
'format:fix',
'prettier',
'prettier:write',
'prettier:fix',
'fix:format',
'lint:format'
];

const candidates = Object.entries(scripts)
.filter(([, command]) => isFormattingOnly(String(command)))
.sort(([a], [b]) => {
const ai = preferredNames.indexOf(a);
const bi = preferredNames.indexOf(b);
return (ai === -1 ? Number.MAX_SAFE_INTEGER : ai) - (bi === -1 ? Number.MAX_SAFE_INTEGER : bi) || a.localeCompare(b);
});

if (requestedScript) {
const command = scripts[requestedScript];
if (!command) {
console.error(`package.json script not found: ${requestedScript}`);
process.exit(1);
}
if (!isFormattingOnly(String(command))) {
console.error(`Refusing to run script "${requestedScript}" because it is not a single-purpose prettier --write script.`);
process.exit(1);
}

console.log('kind=script');
console.log(`script_name=${requestedScript}`);
console.log(`prettier_package=${prettierPackage}`);
process.exit(0);
}

if (formatter === 'package-script') {
if (candidates.length === 0) {
console.error('No single-purpose prettier --write package.json script was found.');
process.exit(1);
}

console.log('kind=script');
console.log(`script_name=${candidates[0][0]}`);
console.log(`prettier_package=${prettierPackage}`);
process.exit(0);
}

if (formatter === 'auto' && targetPath === '.' && candidates.length > 0) {
console.log('kind=script');
console.log(`script_name=${candidates[0][0]}`);
console.log(`prettier_package=${prettierPackage}`);
process.exit(0);
}

console.log('kind=direct');
console.log('script_name=');
console.log(`prettier_package=${prettierPackage}`);
NODE

- name: Detect package manager
id: pm
if: ${{ steps.prettier.outputs.kind == 'script' }}
shell: bash
env:
INPUT_PACKAGE_MANAGER: ${{ inputs.package-manager }}
WORKING_DIRECTORY: ${{ inputs.working-directory }}
run: |
set -euo pipefail
cd "$WORKING_DIRECTORY"

manager="$INPUT_PACKAGE_MANAGER"

if [ "$manager" = "auto" ] || [ -z "$manager" ]; then
manager="$(
node <<'NODE'
const fs = require('node:fs');

let packageJson = {};
try {
packageJson = JSON.parse(fs.readFileSync('package.json', 'utf8'));
} catch {}

const candidates = [
String(packageJson.packageManager || ''),
String(packageJson.devEngines?.packageManager?.name || ''),
String(packageJson.devEngines?.packageManager || '')
];

for (const candidate of candidates) {
if (candidate.startsWith('pnpm@') || candidate === 'pnpm') {
console.log('pnpm');
process.exit(0);
}
if (candidate.startsWith('yarn@') || candidate === 'yarn') {
console.log('yarn');
process.exit(0);
}
if (candidate.startsWith('npm@') || candidate === 'npm') {
console.log('npm');
process.exit(0);
}
}

if (fs.existsSync('pnpm-lock.yaml')) {
console.log('pnpm');
} else if (fs.existsSync('yarn.lock')) {
console.log('yarn');
} else {
console.log('npm');
}
NODE
)"
fi

case "$manager" in
npm|pnpm|yarn) ;;
*)
echo "Unsupported package manager: $manager" >&2
exit 1
;;
esac

echo "manager=$manager" >> "$GITHUB_OUTPUT"
echo "Detected package manager: $manager"

- name: Enable Corepack
if: ${{ steps.prettier.outputs.kind == 'script' && (steps.pm.outputs.manager == 'pnpm' || steps.pm.outputs.manager == 'yarn') }}
shell: bash
run: corepack enable

- name: Install dependencies for package script
if: ${{ steps.prettier.outputs.kind == 'script' }}
shell: bash
env:
PACKAGE_MANAGER: ${{ steps.pm.outputs.manager }}
HUSKY: "0"
WORKING_DIRECTORY: ${{ inputs.working-directory }}
run: |
set -euo pipefail
cd "$WORKING_DIRECTORY"

case "$PACKAGE_MANAGER" in
npm)
if [ -f package-lock.json ] || [ -f npm-shrinkwrap.json ]; then
npm ci
else
npm install
fi
;;
pnpm)
pnpm install --frozen-lockfile
;;
yarn)
yarn install --immutable || yarn install --frozen-lockfile
;;
esac

- name: Run Prettier
shell: bash
env:
PACKAGE_MANAGER: ${{ steps.pm.outputs.manager }}
PRETTIER_PACKAGE: ${{ steps.prettier.outputs.prettier_package }}
PRETTIER_KIND: ${{ steps.prettier.outputs.kind }}
SCRIPT_NAME: ${{ steps.prettier.outputs.script_name }}
TARGET_PATH: ${{ inputs.path }}
WORKING_DIRECTORY: ${{ inputs.working-directory }}
run: |
set -euo pipefail
cd "$WORKING_DIRECTORY"

if [ "$PRETTIER_KIND" = "script" ]; then
case "$PACKAGE_MANAGER" in
npm) npm run "$SCRIPT_NAME" ;;
pnpm) pnpm run "$SCRIPT_NAME" ;;
yarn) yarn run "$SCRIPT_NAME" ;;
esac
exit 0
fi

npm exec --yes --package "$PRETTIER_PACKAGE" -- prettier --write --ignore-unknown -- "$TARGET_PATH"

- name: Create patch
id: diff
shell: bash
env:
WORKING_DIRECTORY: ${{ inputs.working-directory }}
run: |
set -euo pipefail
cd "$WORKING_DIRECTORY"

patch_path="$RUNNER_TEMP/prettier.patch"

if git diff --quiet; then
echo "changed=false" >> "$GITHUB_OUTPUT"
echo "patch_path=$patch_path" >> "$GITHUB_OUTPUT"
echo "No Prettier changes."
exit 0
fi

git status --short
git diff --binary > "$patch_path"
echo "changed=true" >> "$GITHUB_OUTPUT"
echo "patch_path=$patch_path" >> "$GITHUB_OUTPUT"
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