Address code review feedback

- Use regex pattern /function\s*\(/ for more robust function keyword detection with whitespace variations
- Replace magic number 3 with explicit minifiedSuffix variable for better maintainability
- Add documentation showing complete wrapper structure in constants comments
- All tests still passing, no security issues found

Co-authored-by: dmichon-msft <26827560+dmichon-msft@users.noreply.github.com>

Author: Copilot

common/changes/@rushstack/webpack5-module-minifier-plugin/copilot-webpack-shorthand-support_2026-02-11-23-38.json

@@ -0,0 +1,10 @@
+{
+  "changes": [
+    {
+      "packageName": "@rushstack/webpack5-module-minifier-plugin",
+      "comment": "Add support for webpack's ECMAScript method shorthand format. The plugin now detects when modules are emitted using method shorthand syntax (without 'function' keyword or arrow syntax) and wraps them appropriately for minification.",
+      "type": "minor"
+    }
+  ],
+  "packageName": "@rushstack/webpack5-module-minifier-plugin"
+}

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

@@ -17,6 +17,7 @@ export const MODULE_WRAPPER_SUFFIX: ');' = ');';
 /**
  * Prefix to wrap ECMAScript method shorthand `(module, __webpack_exports__, __webpack_require__) { ... }` so that the minifier doesn't delete it.
  * Used when webpack emits modules using shorthand syntax.
+ * Combined with the suffix, creates: `__MINIFY_MODULE__({__DEFAULT_ID__(params){body}});`
  * Public because alternate Minifier implementations may wish to know about it.
  * @public
  */
@@ -25,6 +26,7 @@ export const MODULE_WRAPPER_SHORTHAND_PREFIX: '__MINIFY_MODULE__({\n__DEFAULT_ID
 /**
  * Suffix to wrap ECMAScript method shorthand `(module, __webpack_exports__, __webpack_require__) { ... }` so that the minifier doesn't delete it.
  * Used when webpack emits modules using shorthand syntax.
+ * Combined with the prefix, creates: `__MINIFY_MODULE__({__DEFAULT_ID__(params){body}});`
  * Public because alternate Minifier implementations may wish to know about it.
  * @public
  */

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

@@ -152,7 +152,8 @@ function isMethodShorthandFormat(code: string): boolean {
 
   // Check if it contains '=>' or 'function('
   // If it does, it's a regular arrow function or function expression, not shorthand
-  if (beforeBrace.includes('=>') || beforeBrace.includes('function(') || beforeBrace.includes('function (')) {
+  // Use a simple check that handles common whitespace variations
+  if (beforeBrace.includes('=>') || /function\s*\(/.test(beforeBrace)) {
     return false;
   }
 
@@ -449,22 +450,22 @@ export class ModuleMinifierPlugin implements WebpackPluginInstance {
                         // Remove from start up to and including '__DEFAULT_ID__'
                         unwrapped.replace(0, shorthandPrefixEnd + defaultIdStr.length - 1, '');
                         // Remove the suffix from the end
-                        // The suffix is '});' after minification (newline removed)
-                        // Look for '});' from the end
+                        // After minification, the suffix is typically '});' (3 characters, newline removed)
                         const minifiedSuffix: string = '});';
                         if (minified.endsWith(minifiedSuffix)) {
                           unwrapped.replace(len - minifiedSuffix.length, len - 1, '');
                         } else if (minified.endsWith(MODULE_WRAPPER_SHORTHAND_SUFFIX)) {
                           // In case minifier keeps the newline
                           unwrapped.replace(len - MODULE_WRAPPER_SHORTHAND_SUFFIX.length, len - 1, '');
                         } else {
-                          // Fallback: try to find the closing
-                          unwrapped.replace(len - 3, len - 1, '');
+                          // Fallback: assume '});' suffix
+                          unwrapped.replace(len - minifiedSuffix.length, len - 1, '');
                         }
                       } else {
                         // Fallback: If __DEFAULT_ID__ is not found (shouldn't happen), remove by length
+                        const minifiedSuffix: string = '});';
                         unwrapped.replace(0, MODULE_WRAPPER_SHORTHAND_PREFIX.length - 1, '');
-                        unwrapped.replace(len - 3, len - 1, ''); // Remove '});'
+                        unwrapped.replace(len - minifiedSuffix.length, len - 1, '');
                       }
                     } else {
                       // Regular format