perf(@angular-devkit/build-angular): remove Webpack Stats.toJson usage in analytics plugin

Webpack's Stats.toJson function is an expensive operation and is recommended to be avoided where possible. In the case of the analytics plugin, the chunks and assets can be accessed directly from the Webpack compilation.

Author: clydin

packages/angular_devkit/build_angular/src/webpack/plugins/analytics.ts

@@ -196,16 +196,17 @@ export class NgBuildAnalyticsPlugin {
     }
   }
 
-  // We can safely disable no any here since we know the format of the JSON output from webpack.
-  // tslint:disable-next-line:no-any
-  protected _collectBundleStats(json: any) {
-    json.chunks
+  protected _collectBundleStats(compilation: compilation.Compilation) {
+    // `compilation.chunks` is a Set in Webpack 5
+    const chunks = Array.from(compilation.chunks);
+
+    chunks
       .filter((chunk: { rendered?: boolean }) => chunk.rendered)
-      .forEach((chunk: { files: string[], initial?: boolean, entry?: boolean }) => {
-        const asset = json.assets.find((x: { name: string }) => x.name == chunk.files[0]);
-        const size = asset ? asset.size : 0;
+      .forEach((chunk: { files: string[]; canBeInitial(): boolean }) => {
+        const asset = compilation.assets[chunk.files[0]];
+        const size = asset ? asset.size() : 0;
 
-        if (chunk.entry || chunk.initial) {
+        if (chunk.canBeInitial()) {
           this._stats.initialChunkSize += size;
         } else {
           this._stats.lazyChunkCount++;
@@ -215,24 +216,26 @@ export class NgBuildAnalyticsPlugin {
         this._stats.totalChunkSize += size;
       });
 
-    json.assets
+    Object.entries<{ size(): number }>(compilation.assets)
       // Filter out chunks. We only count assets that are not JS.
-      .filter((a: { name: string }) => {
-        return json.chunks.every((chunk: { files: string[] }) => chunk.files[0] != a.name);
+      .filter(([name]) => {
+        return chunks.every((chunk: { files: string[] }) => chunk.files[0] != name);
       })
-      .forEach((a: { size?: number }) => {
-        this._stats.assetSize += (a.size || 0);
+      .forEach(([, asset]) => {
+        this._stats.assetSize += asset.size();
         this._stats.assetCount++;
       });
 
-    for (const asset of json.assets) {
-      if (asset.name == 'polyfill') {
-        this._stats.polyfillSize += asset.size || 0;
+    for (const [name, asset] of Object.entries<{ size(): number }>(compilation.assets)) {
+      if (name == 'polyfill') {
+        this._stats.polyfillSize += asset.size();
       }
     }
-    for (const chunk of json.chunks) {
+    for (const chunk of compilation.chunks) {
       if (chunk.files[0] && chunk.files[0].endsWith('.css')) {
-        this._stats.cssSize += chunk.size || 0;
+        const asset = compilation.assets[chunk.files[0]];
+        const size = asset ? asset.size() : 0;
+        this._stats.cssSize += size;
       }
     }
   }
@@ -276,7 +279,7 @@ export class NgBuildAnalyticsPlugin {
 
   protected _done(stats: Stats) {
     this._collectErrors(stats);
-    this._collectBundleStats(stats.toJson());
+    this._collectBundleStats(stats.compilation);
     if (this._built) {
       this._reportRebuildMetrics(stats);
     } else {