Fix tightly-coupled dependency on Stylelint's internal module `lib/ut…

…ils/getOsEol` (#66)

This change aims to make changes easier by removing the dependency on an internal module.

Summary:
- Change the `os.EOL` property by the before/all hooks instead of mocking.
- Add a file for `setupFilesAfterEnv`.
- Delay requiring `stylelint` in `getTestRule()`.

See also:
- https://github.com/stylelint/stylelint/blob/0dbed54626e87786c2ef2e4ccd4c27d04c8a6918/lib/utils/getOsEol.js
- https://jestjs.io/docs/configuration/#setupfilesafterenv-array

CHANGELOG.md

@@ -1,5 +1,9 @@
 # Changelog
 
+## Head
+
+- Fixed: tightly-coupled dependency on Stylelint's internal module `lib/utils/getOsEol`.
+
 ## 6.1.0
 
 - Added: support for custom unfixable error messages.

__tests__/__snapshots__/index.test.js.snap

@@ -3,6 +3,7 @@
 exports[`should contain expected keys 1`] = `
 [
   "setupFiles",
+  "setupFilesAfterEnv",
   "testEnvironment",
 ]
 `;

getTestRule.js

@@ -2,8 +2,6 @@
 
 const util = require('util');
 
-const { lint } = require('stylelint'); // eslint-disable-line n/no-unpublished-require -- Avoid auto-install of `stylelint` peer dependency.
-
 /**
  * @typedef {import('.').TestCase} TestCase
  * @typedef {import('.').TestSchema} TestSchema
@@ -12,6 +10,14 @@ const { lint } = require('stylelint'); // eslint-disable-line n/no-unpublished-r
 /** @type {import('.').getTestRule} */
 module.exports = function getTestRule(options = {}) {
 	return function testRule(schema) {
+		/** @type {import('stylelint').lint} */
+		let lint;
+
+		beforeAll(() => {
+			// eslint-disable-next-line n/no-unpublished-require -- Avoid auto-install of `stylelint` peer dependency.
+			lint = require('stylelint').lint;
+		});
+
 		describe(`${schema.ruleName}`, () => {
 			const stylelintConfig = {
 				plugins: options.plugins || schema.plugins,

jest-preset.js

@@ -2,5 +2,6 @@
 
 module.exports = {
 	setupFiles: [require.resolve('./jest-setup.js')],
+	setupFilesAfterEnv: [require.resolve('./jest-setup-after-env.js')],
 	testEnvironment: 'node',
 };

jest-setup-after-env.js

@@ -0,0 +1,18 @@
+'use strict';
+
+const os = require('os');
+
+const eolDescriptor = Object.getOwnPropertyDescriptor(os, 'EOL');
+
+if (!eolDescriptor) {
+	throw new TypeError('`os` must have an `EOL` property');
+}
+
+beforeAll(() => {
+	// NOTE: `jest.replaceProperty()` is unavailable for a read-only property.
+	Object.defineProperty(os, 'EOL', { ...eolDescriptor, value: '\n' });
+});
+
+afterAll(() => {
+	Object.defineProperty(os, 'EOL', eolDescriptor);
+});

jest-setup.js

@@ -1,8 +1,5 @@
 'use strict';
 
-// Mock should be before stylelint required. Even if it's required inside other modules
-jest.mock('stylelint/lib/utils/getOsEol', () => () => '\n');
-
 const getTestRule = require('./getTestRule');
 
 global.testRule = getTestRule();

package.json

@@ -17,6 +17,7 @@
     "getTestRule.js",
     "jest-preset.js",
     "jest-setup.js",
+    "jest-setup-after-env.js",
     "index.d.ts"
   ],
   "scripts": {