fix(@ngtools/webpack): resources path normalizations

Compiler host `readResource` is always called with POSIX seperators. However the `denormalizePath` method doesn't convert forward slashes to back slashes which causes `getModifiedResourceFiles` to return an empty `Set`.

We were also assuming that `_changedFiles` is an FS path which was not the case as it's original type is `Path`

Fix #15012

Author: alan-agius4

packages/angular_devkit/build_angular/test/browser/rebuild_spec_large.ts

@@ -349,14 +349,6 @@ describe('Browser Builder rebuilds', () => {
   });
 
   it('rebuilds AOT factories', async () => {
-    // DISABLED_FOR_IVY - These should pass but require fixes for resource rebuilds
-    //                    https://github.com/angular/angular/pull/30954
-    if (ivyEnabled) {
-      pending('Broken in Ivy.');
-
-      return;
-    }
-
     host.writeMultipleFiles({
       'src/app/app.component.css': `
         @import './imported-styles.css';

packages/ngtools/webpack/src/compiler_host.ts

@@ -91,7 +91,7 @@ export class WebpackCompilerHost implements ts.CompilerHost {
     try {
       exists = this._syncHost.isFile(fullPath);
       if (exists) {
-        this._changedFiles.add(fullPath);
+        this._changedFiles.add(workaroundResolve(fullPath));
       }
     } catch {}
 
@@ -339,16 +339,15 @@ export class WebpackCompilerHost implements ts.CompilerHost {
   }
 
   readResource(fileName: string) {
-    this._readResourceFiles.add(fileName);
+    // These paths are meant to be used by the loader so we must denormalize them
+    const denormalizedFileName = workaroundResolve(fileName);
+    this._readResourceFiles.add(denormalizedFileName);
 
     if (this.directTemplateLoading && (fileName.endsWith('.html') || fileName.endsWith('.svg'))) {
       return this.readFile(fileName);
     }
 
     if (this._resourceLoader) {
-      // These paths are meant to be used by the loader so we must denormalize them.
-      const denormalizedFileName = this.denormalizePath(normalize(fileName));
-
       return this._resourceLoader.get(denormalizedFileName);
     } else {
       return this.readFile(fileName);
@@ -359,14 +358,15 @@ export class WebpackCompilerHost implements ts.CompilerHost {
     const modifiedFiles = new Set<string>();
 
     for (const changedFile of this._changedFiles) {
-      if (this._readResourceFiles.has(changedFile)) {
-        modifiedFiles.add(changedFile);
+      const denormalizedFileName = workaroundResolve(changedFile);
+      if (this._readResourceFiles.has(denormalizedFileName)) {
+        modifiedFiles.add(denormalizedFileName);
       }
 
       if (!this._resourceLoader) {
         continue;
       }
-      for (const resourcePath of this._resourceLoader.getAffectedResources(changedFile)) {
+      for (const resourcePath of this._resourceLoader.getAffectedResources(denormalizedFileName)) {
         modifiedFiles.add(resourcePath);
       }
     }