fix(@ngtools/webpack): don't warn on unused ngsummary

Fix #15626 (comment)

(cherry picked from commit 9b91163)

Author: filipesilva

packages/angular_devkit/build_angular/test/browser/unused-files-warning_spec_large.ts

@@ -66,6 +66,40 @@ describe('Browser Builder unused files warnings', () => {
     await run.stop();
   });
 
+  it('should not show warning when excluded files are unused', async () => {
+    if (veEnabled) {
+      // TODO: https://github.com/angular/angular-cli/issues/15056
+      pending('Only supported in Ivy.');
+
+      return;
+    }
+
+    const ignoredFiles = {
+      'src/file.d.ts': 'export type MyType = number;',
+      'src/file.ngsummary.ts': 'export const hello = 42;',
+      'src/file.ngfactory.ts': 'export const hello = 42;',
+      'src/file.ngstyle.ts': 'export const hello = 42;',
+      'src/file.ng_typecheck__.ts': 'export const hello = 42;',
+    };
+
+    host.writeMultipleFiles(ignoredFiles);
+
+    host.replaceInFile(
+      'src/tsconfig.app.json',
+      '"main.ts"',
+      `"main.ts", ${Object.keys(ignoredFiles).map(f => `"${f.replace('src/', '')}"`).join(',')}`,
+    );
+
+    const logger = new TestLogger('unused-files-warnings');
+    const run = await architect.scheduleTarget(targetSpec, undefined, { logger });
+    const output = await run.result as BrowserBuilderOutput;
+    expect(output.success).toBe(true);
+    expect(logger.includes(warningMessageSuffix)).toBe(false);
+    logger.clear();
+
+    await run.stop();
+  });
+
   it('should not show warning when type files are used', async () => {
     if (veEnabled) {
       // TODO: https://github.com/angular/angular-cli/issues/15056

packages/ngtools/webpack/src/angular_compiler_plugin.ts

@@ -611,7 +611,7 @@ export class AngularCompilerPlugin {
     //   JS file example `@angular/core/core.ngfactory.ts`.
     // - .d.ts files might not have a correspondent JS file due to bundling.
     // - __ng_typecheck__.ts will never be requested.
-    const fileExcludeRegExp = /(\.(d|ngfactory|ngstyle)\.ts|ng_typecheck__\.ts)$/;
+    const fileExcludeRegExp = /(\.(d|ngfactory|ngstyle|ngsummary)\.ts|ng_typecheck__\.ts)$/;
 
     // Start with a set of all the source file names we care about.
     const unusedSourceFileNames = new Set(