fix: avoid rebuilt unnecessary files on windows

package.json

@@ -42,31 +42,31 @@
   },
   "dependencies": {
     "clone": "^2.1.2",
-    "less": "^3.11.1",
+    "less": "^3.11.3",
     "loader-utils": "^2.0.0",
-    "schema-utils": "^2.6.6"
+    "schema-utils": "^2.7.0"
   },
   "devDependencies": {
-    "@babel/cli": "^7.8.4",
-    "@babel/core": "^7.9.6",
-    "@babel/preset-env": "^7.9.6",
+    "@babel/cli": "^7.10.1",
+    "@babel/core": "^7.10.2",
+    "@babel/preset-env": "^7.10.2",
     "@commitlint/cli": "^8.3.5",
     "@commitlint/config-conventional": "^8.3.4",
     "@webpack-contrib/defaults": "^6.3.0",
     "@webpack-contrib/eslint-config-webpack": "^3.0.0",
     "babel-jest": "^26.0.1",
     "cross-env": "^7.0.2",
     "del": "^5.1.0",
-    "del-cli": "^3.0.0",
-    "eslint": "^6.8.0",
+    "del-cli": "^3.0.1",
+    "eslint": "^7.2.0",
     "eslint-config-prettier": "^6.11.0",
-    "eslint-plugin-import": "^2.20.2",
+    "eslint-plugin-import": "^2.21.2",
     "eslint-plugin-prettier": "^3.1.3",
     "husky": "^4.2.5",
     "inspect-loader": "^1.0.0",
     "jest": "^26.0.1",
-    "lint-staged": "^10.2.2",
-    "memfs": "^3.1.2",
+    "lint-staged": "^10.2.9",
+    "memfs": "^3.2.0",
     "npm-run-all": "^4.1.5",
     "prettier": "^2.0.5",
     "standard-version": "^8.0.0",

src/LessError.js

@@ -1,3 +1,5 @@
+import path from 'path';
+
 class LessError extends Error {
   constructor(error) {
     super();
@@ -6,7 +8,9 @@ class LessError extends Error {
       '\n',
       ...LessError.getFileExcerptIfPossible(error),
       error.message.charAt(0).toUpperCase() + error.message.slice(1),
-      `      Error in ${error.filename} (line ${error.line}, column ${error.column})`,
+      `      Error in ${path.normalize(error.filename)} (line ${
+        error.line
+      }, column ${error.column})`,
     ].join('\n');
 
     this.hideStack = true;

src/index.js

@@ -1,3 +1,5 @@
+import path from 'path';
+
 import { getOptions } from 'loader-utils';
 import validateOptions from 'schema-utils';
 
@@ -35,13 +37,19 @@ function lessLoader(source) {
   getLessImplementation(options.implementation)
     .render(data, lessOptions)
     .then(({ css, map, imports }) => {
-      imports.forEach(this.addDependency, this);
+      imports.forEach((item) => {
+        // `less` return forward slashes on windows when `webpack` resolver return an absolute windows path in `WebpackFileManager`
+        // Ref: https://github.com/webpack-contrib/less-loader/issues/357
+        this.addDependency(path.normalize(item));
+      });
 
       callback(null, css, typeof map === 'string' ? JSON.parse(map) : map);
     })
     .catch((lessError) => {
       if (lessError.filename) {
-        this.addDependency(lessError.filename);
+        // `less` return forward slashes on windows when `webpack` resolver return an absolute windows path in `WebpackFileManager`
+        // Ref: https://github.com/webpack-contrib/less-loader/issues/357
+        this.addDependency(path.normalize(lessError.filename));
       }
 
       callback(new LessError(lessError));

test/__snapshots__/loader.test.js.snap

@@ -323,6 +323,17 @@ exports[`loader should transform urls: errors 1`] = `Array []`;
 
 exports[`loader should transform urls: warnings 1`] = `Array []`;
 
+exports[`loader should watch imports correctly: css 1`] = `
+"a {
+  color: red;
+}
+"
+`;
+
+exports[`loader should watch imports correctly: errors 1`] = `Array []`;
+
+exports[`loader should watch imports correctly: warnings 1`] = `Array []`;
+
 exports[`loader should work third-party plugins as fileLoader: css 1`] = `
 ".file-loader {
   background: coral;

test/fixtures/watch.less

@@ -0,0 +1 @@
+@import '~package/style.less';

test/helpers/getCodeFromLess.js

@@ -62,6 +62,14 @@ const pathMap = {
     'fixtures',
     'import-absolute-target.less'
   ),
+  '~package/style.less': path.resolve(
+    __dirname,
+    '..',
+    'fixtures',
+    'node_modules',
+    'package',
+    'style.less'
+  ),
 };
 
 class ResolvePlugin extends less.FileManager {

test/loader.test.js

@@ -461,4 +461,33 @@ describe('loader', () => {
     expect(getWarnings(stats)).toMatchSnapshot('warnings');
     expect(getErrors(stats)).toMatchSnapshot('errors');
   });
+
+  it('should watch imports correctly', async () => {
+    const testId = './watch.less';
+    const compiler = getCompiler(testId);
+    const stats = await compile(compiler);
+    const codeFromBundle = getCodeFromBundle(stats, compiler);
+    const codeFromLess = await getCodeFromLess(testId);
+    const { fileDependencies } = stats.compilation;
+
+    const fixtures = [
+      path.resolve(__dirname, 'fixtures', 'watch.less'),
+      path.resolve(
+        __dirname,
+        'fixtures',
+        'node_modules',
+        'package',
+        'style.less'
+      ),
+    ];
+
+    fixtures.forEach((fixture) => {
+      expect(fileDependencies.has(fixture)).toBe(true);
+    });
+
+    expect(codeFromBundle.css).toBe(codeFromLess.css);
+    expect(codeFromBundle.css).toMatchSnapshot('css');
+    expect(getWarnings(stats)).toMatchSnapshot('warnings');
+    expect(getErrors(stats)).toMatchSnapshot('errors');
+  });
 });