Use Rule.oneOf to resolve correct loader (#2747)

* Use oneOf to resolve correct loader

* Add html and json fallthrough again

* Use oneOf to resolve correct loader in dev

* Document file-loaders `js` exclusion

* Remove `jsx` from exclusion in prod config

Author: Furizaa

packages/react-scripts/config/webpack.config.dev.js

@@ -150,97 +150,95 @@ module.exports = {
         ],
         include: paths.appSrc,
       },
-      // ** ADDING/UPDATING LOADERS **
-      // The "file" loader handles all assets unless explicitly excluded.
-      // The `exclude` list *must* be updated with every change to loader extensions.
-      // When adding a new loader, you must add its `test`
-      // as a new entry in the `exclude` list for "file" loader.
-
-      // "file" loader makes sure those assets get served by WebpackDevServer.
-      // When you `import` an asset, you get its (virtual) filename.
-      // In production, they would get copied to the `build` folder.
-      {
-        exclude: [
-          /\.html$/,
-          /\.(js|jsx)$/,
-          /\.css$/,
-          /\.json$/,
-          /\.bmp$/,
-          /\.gif$/,
-          /\.jpe?g$/,
-          /\.png$/,
-        ],
-        loader: require.resolve('file-loader'),
-        options: {
-          name: 'static/media/[name].[hash:8].[ext]',
-        },
-      },
-      // "url" loader works like "file" loader except that it embeds assets
-      // smaller than specified limit in bytes as data URLs to avoid requests.
-      // A missing `test` is equivalent to a match.
-      {
-        test: [/\.bmp$/, /\.gif$/, /\.jpe?g$/, /\.png$/],
-        loader: require.resolve('url-loader'),
-        options: {
-          limit: 10000,
-          name: 'static/media/[name].[hash:8].[ext]',
-        },
-      },
-      // Process JS with Babel.
       {
-        test: /\.(js|jsx)$/,
-        include: paths.appSrc,
-        loader: require.resolve('babel-loader'),
-        options: {
-          // @remove-on-eject-begin
-          babelrc: false,
-          presets: [require.resolve('babel-preset-react-app')],
-          // @remove-on-eject-end
-          // This is a feature of `babel-loader` for webpack (not Babel itself).
-          // It enables caching results in ./node_modules/.cache/babel-loader/
-          // directory for faster rebuilds.
-          cacheDirectory: true,
-        },
-      },
-      // "postcss" loader applies autoprefixer to our CSS.
-      // "css" loader resolves paths in CSS and adds assets as dependencies.
-      // "style" loader turns CSS into JS modules that inject <style> tags.
-      // In production, we use a plugin to extract that CSS to a file, but
-      // in development "style" loader enables hot editing of CSS.
-      {
-        test: /\.css$/,
-        use: [
-          require.resolve('style-loader'),
+        // "oneOf" will traverse all following loaders until one will
+        // match the requirements. When no loader matches it will fall
+        // back to the "file" loader at the end of the loader list.
+        oneOf: [
+          // "url" loader works like "file" loader except that it embeds assets
+          // smaller than specified limit in bytes as data URLs to avoid requests.
+          // A missing `test` is equivalent to a match.
           {
-            loader: require.resolve('css-loader'),
+            test: [/\.bmp$/, /\.gif$/, /\.jpe?g$/, /\.png$/],
+            loader: require.resolve('url-loader'),
             options: {
-              importLoaders: 1,
+              limit: 10000,
+              name: 'static/media/[name].[hash:8].[ext]',
             },
           },
+          // Process JS with Babel.
           {
-            loader: require.resolve('postcss-loader'),
+            test: /\.(js|jsx)$/,
+            include: paths.appSrc,
+            loader: require.resolve('babel-loader'),
             options: {
-              // Necessary for external CSS imports to work
-              // https://github.com/facebookincubator/create-react-app/issues/2677
-              ident: 'postcss',
-              plugins: () => [
-                require('postcss-flexbugs-fixes'),
-                autoprefixer({
-                  browsers: [
-                    '>1%',
-                    'last 4 versions',
-                    'Firefox ESR',
-                    'not ie < 9', // React doesn't support IE8 anyway
+              // @remove-on-eject-begin
+              babelrc: false,
+              presets: [require.resolve('babel-preset-react-app')],
+              // @remove-on-eject-end
+              // This is a feature of `babel-loader` for webpack (not Babel itself).
+              // It enables caching results in ./node_modules/.cache/babel-loader/
+              // directory for faster rebuilds.
+              cacheDirectory: true,
+            },
+          },
+          // "postcss" loader applies autoprefixer to our CSS.
+          // "css" loader resolves paths in CSS and adds assets as dependencies.
+          // "style" loader turns CSS into JS modules that inject <style> tags.
+          // In production, we use a plugin to extract that CSS to a file, but
+          // in development "style" loader enables hot editing of CSS.
+          {
+            test: /\.css$/,
+            use: [
+              require.resolve('style-loader'),
+              {
+                loader: require.resolve('css-loader'),
+                options: {
+                  importLoaders: 1,
+                },
+              },
+              {
+                loader: require.resolve('postcss-loader'),
+                options: {
+                  // Necessary for external CSS imports to work
+                  // https://github.com/facebookincubator/create-react-app/issues/2677
+                  ident: 'postcss',
+                  plugins: () => [
+                    require('postcss-flexbugs-fixes'),
+                    autoprefixer({
+                      browsers: [
+                        '>1%',
+                        'last 4 versions',
+                        'Firefox ESR',
+                        'not ie < 9', // React doesn't support IE8 anyway
+                      ],
+                      flexbox: 'no-2009',
+                    }),
                   ],
-                  flexbox: 'no-2009',
-                }),
-              ],
+                },
+              },
+            ],
+          },
+          // "file" loader makes sure those assets get served by WebpackDevServer.
+          // When you `import` an asset, you get its (virtual) filename.
+          // In production, they would get copied to the `build` folder.
+          // This loader don't uses a "test" so it will catch all modules
+          // that fall through the other loaders.
+          {
+            // Exclude `js` files to keep "css" loader working as it injects
+            // it's runtime that would otherwise processed through "file" loader.
+            // Also exclude `html` and `json` extensions so they get processed
+            // by webpacks internal loaders.
+            exclude: [/\.js$/, /\.html$/, /\.json$/],
+            loader: require.resolve('file-loader'),
+            options: {
+              name: 'static/media/[name].[hash:8].[ext]',
             },
           },
         ],
       },
       // ** STOP ** Are you adding a new loader?
-      // Remember to add the new extension(s) to the "file" loader exclusion list.
+      // Make sure to add the new loader(s) before the "file" loader.
     ],
   },
   plugins: [

packages/react-scripts/config/webpack.config.prod.js

@@ -152,109 +152,107 @@ module.exports = {
         ],
         include: paths.appSrc,
       },
-      // ** ADDING/UPDATING LOADERS **
-      // The "file" loader handles all assets unless explicitly excluded.
-      // The `exclude` list *must* be updated with every change to loader extensions.
-      // When adding a new loader, you must add its `test`
-      // as a new entry in the `exclude` list in the "file" loader.
-
-      // "file" loader makes sure those assets end up in the `build` folder.
-      // When you `import` an asset, you get its filename.
-      {
-        exclude: [
-          /\.html$/,
-          /\.(js|jsx)$/,
-          /\.css$/,
-          /\.json$/,
-          /\.bmp$/,
-          /\.gif$/,
-          /\.jpe?g$/,
-          /\.png$/,
-        ],
-        loader: require.resolve('file-loader'),
-        options: {
-          name: 'static/media/[name].[hash:8].[ext]',
-        },
-      },
-      // "url" loader works just like "file" loader but it also embeds
-      // assets smaller than specified size as data URLs to avoid requests.
-      {
-        test: [/\.bmp$/, /\.gif$/, /\.jpe?g$/, /\.png$/],
-        loader: require.resolve('url-loader'),
-        options: {
-          limit: 10000,
-          name: 'static/media/[name].[hash:8].[ext]',
-        },
-      },
-      // Process JS with Babel.
-      {
-        test: /\.(js|jsx)$/,
-        include: paths.appSrc,
-        loader: require.resolve('babel-loader'),
-        options: {
-          // @remove-on-eject-begin
-          babelrc: false,
-          presets: [require.resolve('babel-preset-react-app')],
-          // @remove-on-eject-end
-          compact: true,
-        },
-      },
-      // The notation here is somewhat confusing.
-      // "postcss" loader applies autoprefixer to our CSS.
-      // "css" loader resolves paths in CSS and adds assets as dependencies.
-      // "style" loader normally turns CSS into JS modules injecting <style>,
-      // but unlike in development configuration, we do something different.
-      // `ExtractTextPlugin` first applies the "postcss" and "css" loaders
-      // (second argument), then grabs the result CSS and puts it into a
-      // separate file in our build process. This way we actually ship
-      // a single CSS file in production instead of JS code injecting <style>
-      // tags. If you use code splitting, however, any async bundles will still
-      // use the "style" loader inside the async code so CSS from them won't be
-      // in the main CSS file.
       {
-        test: /\.css$/,
-        loader: ExtractTextPlugin.extract(
-          Object.assign(
-            {
-              fallback: require.resolve('style-loader'),
-              use: [
-                {
-                  loader: require.resolve('css-loader'),
-                  options: {
-                    importLoaders: 1,
-                    minimize: true,
-                    sourceMap: true,
-                  },
-                },
+        // "oneOf" will traverse all following loaders until one will
+        // match the requirements. When no loader matches it will fall
+        // back to the "file" loader at the end of the loader list.
+        oneOf: [
+          // "url" loader works just like "file" loader but it also embeds
+          // assets smaller than specified size as data URLs to avoid requests.
+          {
+            test: [/\.bmp$/, /\.gif$/, /\.jpe?g$/, /\.png$/],
+            loader: require.resolve('url-loader'),
+            options: {
+              limit: 10000,
+              name: 'static/media/[name].[hash:8].[ext]',
+            },
+          },
+          // Process JS with Babel.
+          {
+            test: /\.(js|jsx)$/,
+            include: paths.appSrc,
+            loader: require.resolve('babel-loader'),
+            options: {
+              // @remove-on-eject-begin
+              babelrc: false,
+              presets: [require.resolve('babel-preset-react-app')],
+              // @remove-on-eject-end
+              compact: true,
+            },
+          },
+          // The notation here is somewhat confusing.
+          // "postcss" loader applies autoprefixer to our CSS.
+          // "css" loader resolves paths in CSS and adds assets as dependencies.
+          // "style" loader normally turns CSS into JS modules injecting <style>,
+          // but unlike in development configuration, we do something different.
+          // `ExtractTextPlugin` first applies the "postcss" and "css" loaders
+          // (second argument), then grabs the result CSS and puts it into a
+          // separate file in our build process. This way we actually ship
+          // a single CSS file in production instead of JS code injecting <style>
+          // tags. If you use code splitting, however, any async bundles will still
+          // use the "style" loader inside the async code so CSS from them won't be
+          // in the main CSS file.
+          {
+            test: /\.css$/,
+            loader: ExtractTextPlugin.extract(
+              Object.assign(
                 {
-                  loader: require.resolve('postcss-loader'),
-                  options: {
-                    // Necessary for external CSS imports to work
-                    // https://github.com/facebookincubator/create-react-app/issues/2677
-                    ident: 'postcss',
-                    plugins: () => [
-                      require('postcss-flexbugs-fixes'),
-                      autoprefixer({
-                        browsers: [
-                          '>1%',
-                          'last 4 versions',
-                          'Firefox ESR',
-                          'not ie < 9', // React doesn't support IE8 anyway
+                  fallback: require.resolve('style-loader'),
+                  use: [
+                    {
+                      loader: require.resolve('css-loader'),
+                      options: {
+                        importLoaders: 1,
+                        minimize: true,
+                        sourceMap: true,
+                      },
+                    },
+                    {
+                      loader: require.resolve('postcss-loader'),
+                      options: {
+                        // Necessary for external CSS imports to work
+                        // https://github.com/facebookincubator/create-react-app/issues/2677
+                        ident: 'postcss',
+                        plugins: () => [
+                          require('postcss-flexbugs-fixes'),
+                          autoprefixer({
+                            browsers: [
+                              '>1%',
+                              'last 4 versions',
+                              'Firefox ESR',
+                              'not ie < 9', // React doesn't support IE8 anyway
+                            ],
+                            flexbox: 'no-2009',
+                          }),
                         ],
-                        flexbox: 'no-2009',
-                      }),
-                    ],
-                  },
+                      },
+                    },
+                  ],
                 },
-              ],
+                extractTextPluginOptions
+              )
+            ),
+            // Note: this won't work without `new ExtractTextPlugin()` in `plugins`.
+          },
+          // "file" loader makes sure assets end up in the `build` folder.
+          // When you `import` an asset, you get its filename.
+          // This loader don't uses a "test" so it will catch all modules
+          // that fall through the other loaders.
+          {
+            loader: require.resolve('file-loader'),
+            // Exclude `js` files to keep "css" loader working as it injects
+            // it's runtime that would otherwise processed through "file" loader.
+            // Also exclude `html` and `json` extensions so they get processed
+            // by webpacks internal loaders.
+            exclude: [/\.js$/, /\.html$/, /\.json$/],
+            options: {
+              name: 'static/media/[name].[hash:8].[ext]',
             },
-            extractTextPluginOptions
-          )
-        ),
-        // Note: this won't work without `new ExtractTextPlugin()` in `plugins`.
+          },
+          // ** STOP ** Are you adding a new loader?
+          // Make sure to add the new loader(s) before the "file" loader.
+        ],
       },
-      // ** STOP ** Are you adding a new loader?
-      // Remember to add the new extension(s) to the "file" loader exclusion list.
     ],
   },
   plugins: [