[webpack5-module-minifier-plugin] Inline short license comments

common/changes/@rushstack/webpack5-module-minifier-plugin/inline-short-licenses_2026-10-26-19-30.json

@@ -0,0 +1,10 @@
+{
+  "changes": [
+    {
+      "packageName": "@rushstack/webpack5-module-minifier-plugin",
+      "comment": "Add an opt-in `inlineShortLicenses` option to inline complete license comments when they are smaller than the companion-file reference banner, and preserve license banners for chunks containing only inlined modules.",
+      "type": "minor"
+    }
+  ],
+  "packageName": "@rushstack/webpack5-module-minifier-plugin"
+}

common/reviews/api/webpack5-module-minifier-plugin.api.md

@@ -22,7 +22,7 @@ export const CHUNK_MODULE_REGEX: RegExp;
 export const CHUNK_MODULE_TOKEN: '__WEBPACK_CHUNK_MODULE__';
 
 // @public
-export function generateLicenseFileForAsset(compilation: Compilation, asset: IAssetInfo): string;
+export function generateLicenseFileForAsset(compilation: Compilation, asset: IAssetInfo, inlineShortLicenses?: boolean): string;
 
 // @public
 export interface IAssetInfo {
@@ -75,6 +75,7 @@ export interface IModuleMinifierPluginHooks {
 
 // @public
 export interface IModuleMinifierPluginOptions {
+    inlineShortLicenses?: boolean;
     minifier: IModuleMinifier;
     sourceMap?: boolean;
 }

webpack/webpack5-module-minifier-plugin/README.md

@@ -55,6 +55,26 @@ optimization: {
 }
 ```
 
+## License comments
+
+By default, the plugin extracts license comments into a companion `.LICENSE.txt`
+asset and adds a reference banner to the JavaScript chunk.
+
+Set `inlineShortLicenses: true` in the `ModuleMinifierPlugin` options to inline
+the complete license text when it is smaller than that banner. The comparison
+uses UTF-8 byte lengths after deduplicating all license comments in the chunk.
+Equal-size and larger notices remain in companion assets.
+
+```js
+new ModuleMinifierPlugin({
+  minifier: new LocalMinifier(),
+  inlineShortLicenses: true
+});
+```
+
+The decision is made before emitting the companion asset. Inlined comments
+participate in source-map generation, module-position metadata, and content hashes.
+
 ## Links
 
 - [CHANGELOG.md](

webpack/webpack5-module-minifier-plugin/src/GenerateLicenseFileForAsset.ts

@@ -34,13 +34,19 @@ function getAllComments(modules: Iterable<Module>): Set<string> {
 }
 
 /**
- * Generates a companion asset containing all extracted comments. If it is non-empty, returns a banner comment directing users to said companion asset.
+ * Generates a companion asset containing all extracted comments and returns a banner directing users to it,
+ * or returns the comments themselves when short-license inlining is enabled and saves bytes.
  *
  * @param compilation - The webpack compilation
  * @param asset - The asset to process
+ * @param inlineShortLicenses - Inline the complete license text when it is smaller than the reference banner
  * @public
  */
-export function generateLicenseFileForAsset(compilation: Compilation, asset: IAssetInfo): string {
+export function generateLicenseFileForAsset(
+  compilation: Compilation,
+  asset: IAssetInfo,
+  inlineShortLicenses: boolean = false
+): string {
   // Extracted comments from the modules.
   const modules: Iterable<Module> = compilation.chunkGraph.getChunkModulesIterable(asset.chunk);
   const comments: Set<string> = getAllComments(modules);
@@ -50,14 +56,17 @@ export function generateLicenseFileForAsset(compilation: Compilation, asset: IAs
   let banner: string = '';
 
   if (comments.size) {
-    // There are license comments in this chunk, so generate the companion file and inject a banner
     const licenseSource: sources.ConcatSource = new compilation.compiler.webpack.sources.ConcatSource();
     comments.forEach((comment) => {
       licenseSource.add(comment);
     });
     const licenseFileName: string = `${assetName}.LICENSE.txt`;
-    compilation.emitAsset(licenseFileName, licenseSource);
     banner = `/*! For license information please see ${path.basename(licenseFileName)} */\n`;
+    if (inlineShortLicenses && licenseSource.size() < Buffer.byteLength(banner, 'utf8')) {
+      banner = licenseSource.source().toString();
+    } else {
+      compilation.emitAsset(licenseFileName, licenseSource);
+    }
   }
 
   return banner;

webpack/webpack5-module-minifier-plugin/src/ModuleMinifierPlugin.ts

@@ -54,7 +54,7 @@ const PLUGIN_NAME: 'ModuleMinifierPlugin' = 'ModuleMinifierPlugin';
 
 // Monotonically increasing identifier to be incremented any time the code generation logic changes
 // Will be applied to the webpack hash.
-const CODE_GENERATION_REVISION: number = 1;
+const CODE_GENERATION_REVISION: number = 2;
 // Match behavior of terser's "some" option
 // https://github.com/terser/terser/blob/d3d924fa9e4c57bbe286b811c6068bcc7026e902/lib/output.js#L175
 const LICENSE_COMMENT_REGEX: RegExp = /@preserve|@lic|@cc_on|^\**!/i;
@@ -93,7 +93,8 @@ function hashCodeFragment(code: string): string {
  */
 function defaultRehydrateAssets(
   dehydratedAssets: IDehydratedAssets,
-  compilation: Compilation
+  compilation: Compilation,
+  inlineShortLicenses: boolean
 ): IDehydratedAssets {
   const { assets, modules } = dehydratedAssets;
 
@@ -106,7 +107,8 @@ function defaultRehydrateAssets(
 
   // Now assets/modules contain fully minified code. Rehydrate.
   for (const [assetName, info] of assets) {
-    const banner: string = info.type === 'javascript' ? generateLicenseFileForAsset(compilation, info) : '';
+    const banner: string =
+      info.type === 'javascript' ? generateLicenseFileForAsset(compilation, info, inlineShortLicenses) : '';
 
     const replacementSource: sources.Source = rehydrateAsset(compilation, info, modules, banner, true);
     metadataByAssetFileName.set(assetName, {
@@ -188,7 +190,7 @@ export class ModuleMinifierPlugin implements WebpackPluginInstance {
       postProcessCodeFragment: new SyncWaterfallHook(['code', 'context'])
     };
 
-    const { minifier, sourceMap } = options;
+    const { minifier, sourceMap, inlineShortLicenses = false } = options;
 
     this.#optionsForHash = {
       ...options,
@@ -198,7 +200,11 @@ export class ModuleMinifierPlugin implements WebpackPluginInstance {
 
     this.#enhancers = [];
 
-    this.hooks.rehydrateAssets.tap(PLUGIN_NAME, defaultRehydrateAssets);
+    this.hooks.rehydrateAssets.tap(
+      PLUGIN_NAME,
+      (dehydratedAssets: IDehydratedAssets, compilation: Compilation): IDehydratedAssets =>
+        defaultRehydrateAssets(dehydratedAssets, compilation, inlineShortLicenses)
+    );
     this.minifier = minifier;
 
     this.#sourceMap = sourceMap;

webpack/webpack5-module-minifier-plugin/src/ModuleMinifierPlugin.types.ts

@@ -173,6 +173,15 @@ export interface IModuleMinifierPluginOptions {
    * Set to `false` for faster builds at the expense of debuggability.
    */
   sourceMap?: boolean;
+
+  /**
+   * Inline a chunk's deduplicated license comments instead of emitting a companion `.LICENSE.txt` asset
+   * when the complete license text is smaller than the reference banner, measured in UTF-8 bytes.
+   * Equal-size and larger notices remain external.
+   *
+   * @defaultValue `false`
+   */
+  inlineShortLicenses?: boolean;
 }
 
 /**

webpack/webpack5-module-minifier-plugin/src/RehydrateAsset.ts

@@ -26,15 +26,14 @@ export function rehydrateAsset(
   } = compilation.compiler;
 
   const assetCode: string = assetSource.source().toString();
+  const { CachedSource, ConcatSource, ReplaceSource } = sources;
 
   const tokenIndex: number = assetCode.indexOf(CHUNK_MODULE_TOKEN);
   if (tokenIndex < 0) {
-    // This is not a JS asset.
-    return assetSource;
+    // Chunks containing only inlined modules still need their license banner.
+    return banner ? new CachedSource(new ConcatSource(banner, assetSource)) : assetSource;
   }
 
-  const { CachedSource, ConcatSource, ReplaceSource } = sources;
-
   CHUNK_MODULE_REGEX.lastIndex = -1;
   let lastStart: number = 0;