fix(@angular-devkit/build-angular): empty output directory instead of removing

packages/angular_devkit/build_angular/src/builders/browser/specs/output-path_spec.ts

@@ -21,7 +21,7 @@ describe('Browser Builder output path', () => {
   });
   afterEach(async () => host.restore().toPromise());
 
-  it('deletes output path', async () => {
+  it('deletes output path content', async () => {
     // Write a file to the output path to later verify it was deleted.
     await host
       .write(join(host.root(), 'dist/file.txt'), virtualFs.stringToFileBuffer('file'))
@@ -34,14 +34,14 @@ describe('Browser Builder output path', () => {
     const run = await architect.scheduleTarget(target);
     const output = await run.result;
     expect(output.success).toBe(false);
-    expect(await host.exists(join(host.root(), 'dist')).toPromise()).toBe(false);
+    expect(await host.exists(join(host.root(), 'dist/file.txt')).toPromise()).toBe(false);
     await run.stop();
   });
 
-  it('deletes output path and unlink symbolic link', async () => {
+  it('deletes output path content and unlink symbolic link', async () => {
     // Write a file to the output path to later verify it was deleted.
     host.writeMultipleFiles({
-      'src-link/dummy.txt': '',
+      'src-link/a.txt': '',
       'dist/file.txt': virtualFs.stringToFileBuffer('file'),
     });
 
@@ -63,8 +63,8 @@ describe('Browser Builder output path', () => {
     const output = await run.result;
     expect(output.success).toBe(false);
 
-    expect(await host.exists(join(host.root(), 'dist')).toPromise()).toBe(false);
-    expect(await host.exists(join(host.root(), 'src-link')).toPromise()).toBe(true);
+    expect(await host.exists(join(host.root(), 'dist/file.txt')).toPromise()).toBe(false);
+    expect(await host.exists(join(host.root(), 'src-link/a.txt')).toPromise()).toBe(true);
     await run.stop();
   });
 

packages/angular_devkit/build_angular/src/utils/delete-output-dir.ts

@@ -7,7 +7,7 @@
  */
 
 import * as fs from 'fs';
-import { resolve } from 'path';
+import { join, resolve } from 'path';
 
 /**
  * Delete an output directory, but error out if it's the root of the project.
@@ -18,5 +18,19 @@ export function deleteOutputDir(root: string, outputPath: string): void {
     throw new Error('Output path MUST not be project root directory!');
   }
 
-  fs.rmSync(resolvedOutputPath, { force: true, recursive: true, maxRetries: 3 });
+  // Avoid removing the actual directory to avoid errors in cases where the output
+  // directory is mounted or symlinked. Instead the contents are removed.
+  let entries;
+  try {
+    entries = fs.readdirSync(resolvedOutputPath);
+  } catch (error) {
+    if (error instanceof Error && 'code' in error && error.code === 'ENOENT') {
+      return;
+    }
+    throw error;
+  }
+
+  for (const entry of entries) {
+    fs.rmSync(join(resolvedOutputPath, entry), { force: true, recursive: true, maxRetries: 3 });
+  }
 }