perf(@ngtools/webpack): use precalculated dependencies in unused file check

This change uses the newly introduced precalculated file dependencies for each TypeScript file instead of querying TypeScript for the SourceFile's dependencies when performing the unused file check at the end of the build cycle. This change removes the need to recalculate the dependencies for each TypeScript file present in the Webpack compilation.

Author: clydin

packages/ngtools/webpack/src/ivy/plugin.ts

@@ -276,15 +276,12 @@ export class AngularWebpackPlugin {
         const currentUnused = new Set(
           allProgramFiles
             .filter((sourceFile) => !sourceFile.isDeclarationFile)
-            .map((sourceFile) => sourceFile.fileName),
+            .map((sourceFile) => normalizePath(sourceFile.fileName)),
         );
         modules.forEach(({ resource }: compilation.Module & { resource?: string }) => {
-          const sourceFile = resource && builder.getSourceFile(resource);
-          if (!sourceFile) {
-            return;
+          if (resource) {
+            this.markResourceUsed(normalizePath(resource), currentUnused);
           }
-
-          builder.getAllDependencies(sourceFile).forEach((dep) => currentUnused.delete(dep));
         });
         for (const unused of currentUnused) {
           if (previousUnused && previousUnused.has(unused)) {
@@ -304,6 +301,24 @@ export class AngularWebpackPlugin {
     });
   }
 
+  private markResourceUsed(
+    normalizedResourcePath: string,
+    currentUnused: Set<string>,
+  ): void {
+    if (!currentUnused.has(normalizedResourcePath)) {
+      return;
+    }
+
+    currentUnused.delete(normalizedResourcePath);
+    const dependencies = this.fileDependencies.get(normalizedResourcePath);
+    if (!dependencies) {
+      return;
+    }
+    for (const dependency of dependencies) {
+      this.markResourceUsed(normalizePath(dependency), currentUnused);
+    }
+  }
+
   private async rebuildRequiredFiles(
     modules: Iterable<compilation.Module>,
     compilation: WebpackCompilation,
@@ -654,7 +669,7 @@ export class AngularWebpackPlugin {
       }
 
       const dependencies = [
-        ...this.fileDependencies.get(filePath) || [],
+        ...(this.fileDependencies.get(filePath) || []),
         ...getExtraDependencies(sourceFile),
       ].map(externalizePath);