test(ivy): mock the filesystem in ngcc main() integration tests (#25557)

Bazel does not like the filesystem being modified.
This commit a temporary mock filesystem that can be modified as needed.

PR Close #25557

packages/compiler-cli/test/ngcc/ngcc_spec.ts

@@ -6,75 +6,102 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
+import {existsSync, readFileSync, readdirSync, statSync} from 'fs';
+import * as mockFs from 'mock-fs';
 import {join} from 'path';
 
 import {mainNgcc} from '../../src/ngcc/src/main';
 
-import {TestSupport, isInBazel, setup} from '../test_support';
-
-const OUTPUT_PATH = 'node_modules_ngtsc';
-
-describe('ngcc behavioral tests', () => {
+describe('ngcc main()', () => {
   if (!isInBazel()) {
     // These tests should be excluded from the non-Bazel build.
     return;
   }
 
-  // Temporary local debugging aid. Set to `true` to turn on.
-  const preserveOutput = false;
-  const onSpecCompleted = (format: string) => {
-    if (preserveOutput) {
-      const {tmpdir} = require('os');
-      const {cp, mkdir, rm, set} = require('shelljs');
-
-      const tempRootDir = join(tmpdir(), 'ngcc-spec', format);
-      const outputDir = OUTPUT_PATH;
-
-      set('-e');
-      rm('-rf', tempRootDir);
-      mkdir('-p', tempRootDir);
-      cp('-R', join(support.basePath, outputDir), tempRootDir);
-
-      global.console.log(`Copied '${outputDir}' to '${tempRootDir}'.`);
-    }
-  };
-
-  let support: TestSupport;
-  beforeEach(() => support = setup());
+  beforeEach(createMockFileSystem);
+  afterEach(restoreRealFileSystem);
 
   it('should run ngcc without errors for fesm2015', () => {
-    const commonPath = join(support.basePath, 'node_modules/@angular/common');
+    const commonPath = join('/node_modules/@angular/common');
     const format = 'fesm2015';
-
-    expect(mainNgcc([format, commonPath, OUTPUT_PATH])).toBe(0);
-
-    onSpecCompleted(format);
+    expect(mainNgcc([format, commonPath])).toBe(0);
   });
 
   it('should run ngcc without errors for fesm5', () => {
-    const commonPath = join(support.basePath, 'node_modules/@angular/common');
+    const commonPath = join('/node_modules/@angular/common');
     const format = 'fesm5';
-
-    expect(mainNgcc([format, commonPath, OUTPUT_PATH])).toBe(0);
-
-    onSpecCompleted(format);
+    expect(mainNgcc([format, commonPath])).toBe(0);
   });
 
   it('should run ngcc without errors for esm2015', () => {
-    const commonPath = join(support.basePath, 'node_modules/@angular/common');
+    const commonPath = join('/node_modules/@angular/common');
     const format = 'esm2015';
-
-    expect(mainNgcc([format, commonPath, OUTPUT_PATH])).toBe(0);
-
-    onSpecCompleted(format);
+    expect(mainNgcc([format, commonPath])).toBe(0);
   });
 
   it('should run ngcc without errors for esm5', () => {
-    const commonPath = join(support.basePath, 'node_modules/@angular/common');
+    const commonPath = join('/node_modules/@angular/common');
     const format = 'esm5';
-
-    expect(mainNgcc([format, commonPath, OUTPUT_PATH])).toBe(0);
-
-    onSpecCompleted(format);
+    expect(mainNgcc([format, commonPath])).toBe(0);
   });
 });
+
+
+function createMockFileSystem() {
+  const packagesPath = join(process.env.TEST_SRCDIR, 'angular/packages');
+  mockFs({'/node_modules/@angular': loadPackages(packagesPath)});
+}
+
+function restoreRealFileSystem() {
+  mockFs.restore();
+}
+
+
+/**
+ * Load the built Angular packages into an in-memory structure.
+ * @param packagesPath the path to the folder containing the built packages.
+ */
+function loadPackages(packagesPath: string): Directory {
+  const packagesDirectory: Directory = {};
+  readdirSync(packagesPath).forEach(name => {
+    const packagePath = join(packagesPath, name);
+    if (!statSync(packagePath).isDirectory()) {
+      return;
+    }
+    const npmPackagePath = join(packagePath, 'npm_package');
+    if (!existsSync(npmPackagePath)) {
+      return;
+    }
+    packagesDirectory[name] = loadDirectory(npmPackagePath);
+  });
+  return packagesDirectory;
+}
+
+
+/**
+ * Load real files from the filesystem into an "in-memory" structure,
+ * which can be used with `mock-fs`.
+ * @param directoryPath the path to the directory we want to load.
+ */
+function loadDirectory(directoryPath: string): Directory {
+  const directory: Directory = {};
+
+  readdirSync(directoryPath).forEach(item => {
+    const itemPath = join(directoryPath, item);
+    if (statSync(itemPath).isDirectory()) {
+      directory[item] = loadDirectory(itemPath);
+    } else {
+      directory[item] = readFileSync(itemPath, 'utf-8');
+    }
+  });
+
+  return directory;
+}
+
+interface Directory {
+  [pathSegment: string]: string|Directory;
+}
+
+function isInBazel() {
+  return process.env.TEST_SRCDIR != null;
+}