fix: ngcc should not run in tsconfig.json directory

`ngcc` should be run in the directory where it is resolved to, not the
directory where `tsconfig.json` is located.

Fix #1039

Author: kyliau

scripts/test.sh

@@ -8,6 +8,10 @@ set -ex -o pipefail
   yarn
   yarn ngcc
 )
+(
+  cd integration/workspace
+  yarn
+)
 
 # Server unit tests
 yarn run test

server/src/ngcc.ts

@@ -7,7 +7,7 @@
  */
 
 import {fork} from 'child_process';
-import * as path from 'path';
+import {dirname, resolve} from 'path';
 
 function resolveNgccFrom(directory: string): string|null {
   try {
@@ -28,19 +28,25 @@ interface Progress {
  * run ngcc.
  */
 export async function resolveAndRunNgcc(tsconfig: string, progress: Progress): Promise<void> {
-  const directory = path.dirname(tsconfig);
+  const directory = dirname(tsconfig);
   const ngcc = resolveNgccFrom(directory);
   if (!ngcc) {
     throw new Error(`Failed to resolve ngcc from ${directory}`);
   }
+  const index = ngcc.lastIndexOf('node_modules');
+  // By default, ngcc assumes the node_modules directory that it needs to process
+  // is in the cwd. In our case, we should set cwd to the directory where ngcc
+  // is resolved to, not the directory where tsconfig.json is located. See
+  // https://github.com/angular/angular/blob/e23fd1f38205410e0ecb601ec73847cea2dea2a8/packages/compiler-cli/ngcc/src/command_line_options.ts#L18-L24
+  const cwd = index > 0 ? ngcc.slice(0, index) : process.cwd();
   const childProcess = fork(
       ngcc,
       [
         '--tsconfig',
         tsconfig,
       ],
       {
-        cwd: directory,
+        cwd: resolve(cwd),
       });
 
   let stderr = '';

server/src/tests/ngcc_spec.ts

@@ -0,0 +1,35 @@
+/**
+ * @license
+ * Copyright Google Inc. All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+
+import * as child_process from 'child_process';
+import {EventEmitter} from 'events';
+import {join, resolve} from 'path';
+
+import {resolveAndRunNgcc} from '../ngcc';
+
+const PACKAGE_ROOT = resolve(__dirname, '../../..');
+const WORKSPACE_ROOT = join(PACKAGE_ROOT, 'integration', 'workspace');
+const PROJECT = join(WORKSPACE_ROOT, 'projects', 'demo');
+
+describe('resolveAndRunNgcc', () => {
+  it('runs ngcc from node_modules where ngcc is resolved to', async () => {
+    const fakeChild = new EventEmitter();
+    const spy = spyOn(child_process, 'fork').and.returnValue(fakeChild as any);
+    // Note that tsconfig.json is in the project directory
+    const tsconfig = join(PROJECT, 'tsconfig.json');
+    const promise = resolveAndRunNgcc(tsconfig, {report() {}});
+    fakeChild.emit('close', 0 /* exit code */);
+    await expectAsync(promise).toBeResolved();
+    expect(spy.calls.count()).toBe(1);
+    // First arg is the ngcc binary, second arg is program arguments, third
+    // arg is fork options.
+    const {cwd} = spy.calls.argsFor(0)[2]!;
+    // cwd for ngcc should be in the workspace directory
+    expect(cwd).toBe(WORKSPACE_ROOT);
+  });
+});