Add support for .postcss files

fixtures/css/postcss_extension.postcss

@@ -0,0 +1 @@
+@import "autoprefixer_test.css";

fixtures/vuejs-css-modules/App.vue

@@ -1,5 +1,5 @@
 <template>
-  <div id="app" class="red large justified lowercase" :class="[$css.italic, $scss.bold, $less.underline, $stylus.rtl]"></div>
+  <div id="app" class="red large justified lowercase block" :class="[$css.italic, $scss.bold, $less.underline, $stylus.rtl, $postcss.hidden]"></div>
 </template>
 
 <style>
@@ -25,6 +25,13 @@
     text-transform: lowercase
 </style>
 
+<style lang="postcss">
+  .block {
+    display: block;
+  }
+</style>
+
+
 <style module="$css">
   .italic {
     font-style: italic;
@@ -46,4 +53,10 @@
 <style lang="styl" module="$stylus">
   .rtl
     direction: rtl;
+</style>
+
+<style lang="postcss" module="$postcss">
+  .hidden {
+    visibility: hidden;
+  }
 </style>

lib/config-generator.js

@@ -236,6 +236,15 @@ class ConfigGenerator {
             return applyOptionsCallback(this.webpackConfig.loaderConfigurationCallbacks[name], defaultRules);
         };
 
+        // When the PostCSS loader is enabled, allow to use
+        // files with the `.postcss` extension. It also
+        // makes it possible to use `lang="postcss"` in Vue
+        // files.
+        const cssExtensions = ['css'];
+        if (this.webpackConfig.usePostCssLoader) {
+            cssExtensions.push('postcss');
+        }
+
         let rules = [
             applyRuleConfigurationCallback('javascript', {
                 // match .js and .jsx
@@ -246,9 +255,9 @@ class ConfigGenerator {
             applyRuleConfigurationCallback('css', {
                 resolve: {
                     mainFields: ['style', 'main'],
-                    extensions: ['.css'],
+                    extensions: cssExtensions.map(ext => `.${ext}`),
                 },
-                test: /\.css$/,
+                test: new RegExp(`\\.(${cssExtensions.join('|')})$`),
                 oneOf: [
                     {
                         resourceQuery: /module/,

test/config-generator.js

@@ -1052,7 +1052,7 @@ describe('The config-generator function', () => {
             });
 
             const webpackConfig = configGenerator(config);
-            const rule = findRule(/\.css$/, webpackConfig.module.rules);
+            const rule = findRule(/\.(css)$/, webpackConfig.module.rules);
 
             expect(rule.camelCase).to.be.true;
         });
@@ -1210,4 +1210,42 @@ describe('The config-generator function', () => {
             expect(rule.use[0].options.fooBar).to.be.equal('fooBar');
         });
     });
+
+    describe('enablePostCssLoader() makes the CSS rule process .postcss file', () => {
+        it('without enablePostCssLoader()', () => {
+            const config = createConfig();
+            config.outputPath = '/tmp/output/public-path';
+            config.publicPath = '/public-path';
+            config.enableSingleRuntimeChunk();
+            config.addEntry('main', './main');
+            // do not call disableImagesLoader
+
+            const actualConfig = configGenerator(config);
+
+            expect(function() {
+                findRule(/\.(css)$/, actualConfig.module.rules);
+            }).not.to.throw();
+            expect(function() {
+                findRule(/\.(css|postcss)$/, actualConfig.module.rules);
+            }).to.throw();
+        });
+
+        it('with enablePostCssLoader()', () => {
+            const config = createConfig();
+            config.outputPath = '/tmp/output/public-path';
+            config.publicPath = '/public-path';
+            config.addEntry('main', './main');
+            config.enableSingleRuntimeChunk();
+            config.enablePostCssLoader();
+
+            const actualConfig = configGenerator(config);
+
+            expect(function() {
+                findRule(/\.(css)$/, actualConfig.module.rules);
+            }).to.throw();
+            expect(function() {
+                findRule(/\.(css|postcss)$/, actualConfig.module.rules);
+            }).to.not.throw();
+        });
+    });
 });

test/functional.js

@@ -948,6 +948,7 @@ module.exports = {
             // load a file that @import's another file, so that we can
             // test that @import resources are parsed through postcss
             config.addStyleEntry('styles', ['./css/imports_autoprefixer.css']);
+            config.addStyleEntry('postcss', './css/postcss_extension.postcss');
             config.enablePostCssLoader();
 
             testSetup.runWebpack(config, (webpackAssert) => {
@@ -957,6 +958,14 @@ module.exports = {
                     '-webkit-full-screen'
                 );
 
+                // check that the .postcss file was also processed
+                // correctly (it also @import the autoprefixer_test.css
+                // file)
+                webpackAssert.assertOutputFileContains(
+                    'postcss.css',
+                    '-webkit-full-screen'
+                );
+
                 done();
             });
         });
@@ -1421,7 +1430,7 @@ module.exports = {
             });
         });
 
-        it('Vue.js supports CSS/Sass/Less/Stylus modules', (done) => {
+        it('Vue.js supports CSS/Sass/Less/Stylus/PostCSS modules', (done) => {
             const appDir = testSetup.createTestAppDir();
             const config = testSetup.createWebpackConfig(appDir, 'www/build', 'dev');
             config.enableSingleRuntimeChunk();
@@ -1437,6 +1446,18 @@ module.exports = {
                 options.localIdentName = '[local]_foo';
             });
 
+            // Enable the PostCSS loader so we can use `lang="postcss"`
+            config.enablePostCssLoader();
+            fs.writeFileSync(
+                path.join(appDir, 'postcss.config.js'),
+                `
+module.exports = {
+  plugins: [
+    require('autoprefixer')()
+  ]
+}                            `
+            );
+
             testSetup.runWebpack(config, (webpackAssert) => {
                 expect(config.outputPath).to.be.a.directory().with.deep.files([
                     'main.js',
@@ -1457,11 +1478,13 @@ module.exports = {
                 expectClassDeclaration('large'); // Standard SCSS
                 expectClassDeclaration('justified'); // Standard Less
                 expectClassDeclaration('lowercase'); // Standard Stylus
+                expectClassDeclaration('block'); // Standard Postcss
 
                 expectClassDeclaration('italic_foo'); // CSS Module
                 expectClassDeclaration('bold_foo'); // SCSS Module
                 expectClassDeclaration('underline_foo'); // Less Module
                 expectClassDeclaration('rtl_foo'); // Stylus Module
+                expectClassDeclaration('hidden_foo'); // Stylus Module
 
                 testSetup.requestTestPage(
                     path.join(config.getContext(), 'www'),
@@ -1474,11 +1497,13 @@ module.exports = {
                         browser.assert.hasClass('#app', 'large'); // Standard SCSS
                         browser.assert.hasClass('#app', 'justified'); // Standard Less
                         browser.assert.hasClass('#app', 'lowercase'); // Standard Stylus
+                        browser.assert.hasClass('#app', 'block'); // Standard Stylus
 
                         browser.assert.hasClass('#app', 'italic_foo'); // CSS module
                         browser.assert.hasClass('#app', 'bold_foo'); // SCSS module
                         browser.assert.hasClass('#app', 'underline_foo'); // Less module
                         browser.assert.hasClass('#app', 'rtl_foo'); // Stylus module
+                        browser.assert.hasClass('#app', 'hidden_foo'); // Stylus module
 
                         done();
                     }