fixup! perf(@angular/build): optimize library dts bundling and enable dts tree-shaking

Author: alan-agius4

packages/angular/build/src/builders/library/pipeline/bundler.ts

@@ -360,7 +360,7 @@ async function executeMultiBundle(
     cwd: workspaceRoot,
     tsconfig: false,
     plugins,
-    treeshake: isDts ? { moduleSideEffects: false } : false,
+    treeshake: isDts,
     resolve: { symlinks: !preserveSymlinks },
     checks: { circularDependency: false, pluginTimings: false },
     onLog(level, log) {

packages/angular/build/src/builders/library/pipeline/bundler_spec.ts

@@ -127,6 +127,47 @@ describe('bundleEntryPoints', () => {
     );
   });
 
+  it('should preserve declare global and module augmentations in side-effect .d.ts imports', async () => {
+    const primaryEntry: NormalizedEntryPoint = {
+      subpath: '.',
+      name: 'my-lib',
+      displayName: 'my-lib',
+      bundleName: 'my-lib',
+      entryFilePath: `${workspaceRoot}/src/public-api.ts`,
+      isPrimary: true,
+    };
+    const entryPoints = new Map<string, NormalizedEntryPoint>([['my-lib', primaryEntry]]);
+
+    const esmFiles = new Map<string, string>([
+      [`${workspaceRoot}/src/public-api.js`, 'export const a = 1;'],
+    ]);
+    const dtsFiles = new Map<string, string>([
+      [
+        `${workspaceRoot}/src/globals.d.ts`,
+        'export {};\ndeclare global {\n  interface Window {\n    myCustomGlobal: boolean;\n  }\n}\n',
+      ],
+      [
+        `${workspaceRoot}/src/augment.d.ts`,
+        "declare module '@angular/core' {\n  interface Component {\n    augmentedProp?: string;\n  }\n}\nexport {};\n",
+      ],
+      [
+        `${workspaceRoot}/src/public-api.d.ts`,
+        'import "./globals.js";\nexport * from "./augment.js";\nexport declare const a = 1;\n',
+      ],
+    ]);
+
+    const output = await bundleEntryPoints(
+      [{ entryPoint: primaryEntry, hasEsmChanges: true, hasDtsChanges: true }],
+      esmFiles,
+      dtsFiles,
+      createOptions(entryPoints),
+    );
+
+    const dtsFile = output.filesToEmit.find((f) => f.path === 'types/my-lib.d.ts');
+    expect(dtsFile?.contents).toContain('myCustomGlobal');
+    expect(dtsFile?.contents).toContain('augmentedProp');
+  });
+
   it('should preserve legal comments in emitted FESM2022 .mjs bundles', async () => {
     const primaryEntry: NormalizedEntryPoint = {
       subpath: '.',