Improve performance of isPathIgnored() utility

[ybiquitous]

Which issue, if any, is this issue related to?

None.

Is there anything in the PR that needs further explanation?

This change delays the getFileIgnorer() call until needed. getFileIgnorer() internally uses fs.readFileSync() which is a blocking I/O and possibly slow.

stylelint/lib/utils/getFileIgnorer.js

Line 30 in 0bc53af

const ignoreText = fs.readFileSync(absoluteIgnoreFilePath, 'utf8');

Benchmark

script

// bench.js
const Benchmark = require('benchmark');
const createStylelint = require('./lib/createStylelint');
const isPathIgnored = require('./lib/isPathIgnored');

const config = {
	ignoreFiles: ['**/*.css', '!**/invalid-hex.css'],
	rules: { 'block-no-empty': true },
};
const stylelint = createStylelint({ config });

const suite = new Benchmark.Suite();

suite
	.add('isPathIgnored', function () {
		isPathIgnored(stylelint, 'a.css');
	})
	.on('complete', function (event) {
		console.log(String(event.target));
	})
	.run({ async: true });

Commit	Result
0bc53af (main branch)	isPathIgnored x 42,235 ops/sec ±2.42% (70 runs sampled)
b6cea75 (this branch)	isPathIgnored x 2,966,362 ops/sec ±1.39% (77 runs sampled)

Environment:

• OS: macOS 13.2.1 (Apple M1 Pro)
• Node.js: 19.8.1

[changeset-bot]

🦋 Changeset detected

Latest commit: c055ba8

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
stylelint	Patch

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[ybiquitous]

[note] Clarify using LinterOptions.

[ybiquitous]

[note] Reduce the ignorer.add() call.

[mattxwang]

LGTM, and thank you for the incremental improvements elsewhere in getFileIgnorer.

I'm surprised that this is in the ballpark of a 75x speedup!

[ybiquitous]

Thanks for the review!