Enable production source maps for index.js, fix CSS sourcemaps (#27291)

Previously, the production build never output sourcemaps. Now we emit
one file for `index.js` because it is the most likely one where we need
to be able to better debug reported issues like
https://github.com/go-gitea/gitea/issues/27213. This will currently
increase the binary size of gitea by around 700kB which is what the
gzipped source map file has.

Also, I fixed the CSS sourcemap generation which was broken since the
introduction of lightningcss.

3 files changed, 30 insertions, 11 deletions

diff --git a/docs/content/installation/from-source.en-us.md b/docs/content/installation/from-source.en-us.md
index ef720f0824..f6a95e8d0c 100644
--- a/docs/content/installation/from-source.en-us.md
+++ b/docs/content/installation/from-source.en-us.md
@@ -128,8 +128,6 @@ If pre-built frontend files are present it is possible to only build the backend
 TAGS="bindata" make backend
 ```
 
-Webpack source maps are by default enabled in development builds and disabled in production builds. They can be enabled by setting the `ENABLE_SOURCEMAP=true` environment variable.
-
 ## Test
 
 After following the steps above, a `gitea` binary will be available in the working directory.
@@ -260,3 +258,11 @@ GOARCH=amd64 \
 TAGS="bindata sqlite sqlite_unlock_notify" \
 make build
 ```
+
+## Source Maps
+
+By default, gitea generates reduced source maps for frontend files to conserve space. This can be controlled with the `ENABLE_SOURCEMAP` environment variable:
+
+- `ENABLE_SOURCEMAP=true` generates all source maps, the default for development builds
+- `ENABLE_SOURCEMAP=reduced` generates limited source maps, the default for production builds
+- `ENABLE_SOURCEMAP=false` generates no source maps
diff --git a/docs/content/installation/from-source.zh-cn.md b/docs/content/installation/from-source.zh-cn.md
index 260ccbee3c..74f76652db 100644
--- a/docs/content/installation/from-source.zh-cn.md
+++ b/docs/content/installation/from-source.zh-cn.md
@@ -100,8 +100,6 @@ TAGS="bindata sqlite sqlite_unlock_notify" make build
 TAGS="bindata" make backend
 ```
 
-在开发构建中，默认启用 Webpack 源映射，在生产构建中禁用。可以通过设置`ENABLE_SOURCEMAP=true`环境变量来启用它们。
-
 ## 测试
 
 按照上述步骤完成后，工作目录中将会有一个`gitea`二进制文件。可以从该目录进行测试，或将其移动到带有测试数据的目录中。当手动从命令行启动 Gitea 时，可以通过按下`Ctrl + C`来停止程序。
@@ -221,3 +219,11 @@ GOARCH=amd64 \
 TAGS="bindata sqlite sqlite_unlock_notify" \
 make build
 ```
+
+## 源映射
+
+默认情况下，gitea 会为前端文件生成精简的源映射以节省空间。 这可以通过“ENABLE_SOURCEMAP”环境变量进行控制：
+
+- `ENABLE_SOURCEMAP=true` 生成所有源映射，这是开发版本的默认设置
+- `ENABLE_SOURCEMAP=reduced` 生成有限的源映射，这是生产版本的默认设置
+- `ENABLE_SOURCEMAP=false` 不生成源映射
diff --git a/webpack.config.js b/webpack.config.js
index f95296c380..448dc64003 100644
--- a/webpack.config.js
+++ b/webpack.config.js
@@ -28,11 +28,15 @@ for (const path of glob('web_src/css/themes/*.css')) {
 
 const isProduction = env.NODE_ENV !== 'development';
 
-let sourceMapEnabled;
+// ENABLE_SOURCEMAP accepts the following values:
+// true - all enabled, the default in development
+// reduced - minimal sourcemaps, the default in production
+// false - all disabled
+let sourceMaps;
 if ('ENABLE_SOURCEMAP' in env) {
-  sourceMapEnabled = env.ENABLE_SOURCEMAP === 'true';
+  sourceMaps = ['true', 'false'].includes(env.ENABLE_SOURCEMAP) ? env.ENABLE_SOURCEMAP : 'reduced';
 } else {
-  sourceMapEnabled = !isProduction;
+  sourceMaps = isProduction ? 'reduced' : 'true';
 }
 
 const filterCssImport = (url, ...args) => {
@@ -105,7 +109,9 @@ export default {
         css: !LightningCssMinifyPlugin,
         legalComments: 'none',
       }),
-      LightningCssMinifyPlugin && new LightningCssMinifyPlugin(),
+      LightningCssMinifyPlugin && new LightningCssMinifyPlugin({
+        sourceMap: sourceMaps === 'true',
+      }),
     ],
     splitChunks: {
       chunks: 'async',
@@ -143,7 +149,7 @@ export default {
           {
             loader: 'css-loader',
             options: {
-              sourceMap: sourceMapEnabled,
+              sourceMap: sourceMaps === 'true',
               url: {filter: filterCssImport},
               import: {filter: filterCssImport},
             },
@@ -181,9 +187,10 @@ export default {
       filename: 'css/[name].css',
       chunkFilename: 'css/[name].[contenthash:8].css',
     }),
-    sourceMapEnabled && (new SourceMapDevToolPlugin({
+    sourceMaps !== 'false' && new SourceMapDevToolPlugin({
       filename: '[file].[contenthash:8].map',
-    })),
+      ...(sourceMaps === 'reduced' && {include: /^js\/index\.js$/}),
+    }),
     new MonacoWebpackPlugin({
       filename: 'js/monaco-[name].[contenthash:8].worker.js',
     }),