Final cleanup: strictNullChecks compliance, template types, and indexOf pattern

- MockMinifier: Use local function with multiple returns for strictNullChecks compliance
- Constants: Use template string types for MODULE_WRAPPER_SHORTHAND_PREFIX/SUFFIX to show exact types in API docs
- ModuleMinifierPlugin: Change indexOf check from === -1 to < 0 (more concise, language-friendly)
- All 7 tests passing with zero syntax errors

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

Author: Copilot

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

@@ -112,10 +112,10 @@ export interface IRenderedModulePosition {
 export const MODULE_WRAPPER_PREFIX: '__MINIFY_MODULE__(';
 
 // @public
-export const MODULE_WRAPPER_SHORTHAND_PREFIX: string;
+export const MODULE_WRAPPER_SHORTHAND_PREFIX: `${typeof MODULE_WRAPPER_PREFIX}{__DEFAULT_ID__`;
 
 // @public
-export const MODULE_WRAPPER_SHORTHAND_SUFFIX: string;
+export const MODULE_WRAPPER_SHORTHAND_SUFFIX: `}${typeof MODULE_WRAPPER_SUFFIX}`;
 
 // @public
 export const MODULE_WRAPPER_SUFFIX: ');';

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

@@ -21,15 +21,15 @@ export const MODULE_WRAPPER_SUFFIX: ');' = ');';
  * Public because alternate Minifier implementations may wish to know about it.
  * @public
  */
-export const MODULE_WRAPPER_SHORTHAND_PREFIX: string = `${MODULE_WRAPPER_PREFIX}{__DEFAULT_ID__`;
+export const MODULE_WRAPPER_SHORTHAND_PREFIX: `${typeof MODULE_WRAPPER_PREFIX}{__DEFAULT_ID__` = `${MODULE_WRAPPER_PREFIX}{__DEFAULT_ID__`;
 /**
  * Suffix to wrap ECMAScript method shorthand `(module, __webpack_exports__, __webpack_require__) { ... }` so that the minifier doesn't delete it.
  * Used when webpack emits modules using shorthand syntax.
  * Combined with the prefix, creates: `__MINIFY_MODULE__({__DEFAULT_ID__(params){body}});`
  * Public because alternate Minifier implementations may wish to know about it.
  * @public
  */
-export const MODULE_WRAPPER_SHORTHAND_SUFFIX: string = `}${MODULE_WRAPPER_SUFFIX}`;
+export const MODULE_WRAPPER_SHORTHAND_SUFFIX: `}${typeof MODULE_WRAPPER_SUFFIX}` = `}${MODULE_WRAPPER_SUFFIX}`;
 
 /**
  * Token preceding a module id in the emitted asset so the minifier can operate on the Webpack runtime or chunk boilerplate in isolation

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

@@ -147,7 +147,7 @@ const FUNCTION_KEYWORD_REGEX: RegExp = /function\s*\(/;
 function isMethodShorthandFormat(code: string): boolean {
   // Find the position of the first opening brace
   const firstBraceIndex: number = code.indexOf('{');
-  if (firstBraceIndex === -1) {
+  if (firstBraceIndex < 0) {
     // No brace found, not a function format
     return false;
   }

webpack/webpack5-module-minifier-plugin/src/test/MockMinifier.ts

@@ -31,25 +31,29 @@ export class MockMinifier implements IModuleMinifier {
     const isModule: boolean = code.startsWith(MODULE_WRAPPER_PREFIX);
     const isShorthandModule: boolean = code.startsWith(MODULE_WRAPPER_SHORTHAND_PREFIX);
 
-    let processedCode: string;
-    if (isShorthandModule) {
-      // Handle shorthand format
-      // Add comment markers similar to regular format
-      const innerCode: string = code.slice(
-        MODULE_WRAPPER_SHORTHAND_PREFIX.length,
-        -MODULE_WRAPPER_SHORTHAND_SUFFIX.length
-      );
-      processedCode = `${MODULE_WRAPPER_SHORTHAND_PREFIX}\n// Begin Module Hash=${hash}\n${innerCode}\n// End Module\n${MODULE_WRAPPER_SHORTHAND_SUFFIX}`;
-    } else if (isModule) {
-      // Handle regular format
-      processedCode = `${MODULE_WRAPPER_PREFIX}\n// Begin Module Hash=${hash}\n${code.slice(
-        MODULE_WRAPPER_PREFIX.length,
-        -MODULE_WRAPPER_SUFFIX.length
-      )}\n// End Module${MODULE_WRAPPER_SUFFIX}`;
-    } else {
-      // Handle asset format
-      processedCode = `// Begin Asset Hash=${hash}\n${code}\n// End Asset`;
-    }
+    // Use local function to ensure processedCode is always initialized (strictNullChecks compliant)
+    const getProcessedCode = (): string => {
+      if (isShorthandModule) {
+        // Handle shorthand format
+        // Add comment markers similar to regular format
+        const innerCode: string = code.slice(
+          MODULE_WRAPPER_SHORTHAND_PREFIX.length,
+          -MODULE_WRAPPER_SHORTHAND_SUFFIX.length
+        );
+        return `${MODULE_WRAPPER_SHORTHAND_PREFIX}\n// Begin Module Hash=${hash}\n${innerCode}\n// End Module\n${MODULE_WRAPPER_SHORTHAND_SUFFIX}`;
+      } else if (isModule) {
+        // Handle regular format
+        return `${MODULE_WRAPPER_PREFIX}\n// Begin Module Hash=${hash}\n${code.slice(
+          MODULE_WRAPPER_PREFIX.length,
+          -MODULE_WRAPPER_SUFFIX.length
+        )}\n// End Module${MODULE_WRAPPER_SUFFIX}`;
+      } else {
+        // Handle asset format
+        return `// Begin Asset Hash=${hash}\n${code}\n// End Asset`;
+      }
+    };
+
+    const processedCode: string = getProcessedCode();
 
     callback({
       hash,