fix(ng-update): properly handle update from different working directory

src/cdk/schematics/ng-update/devkit-migration-rule.ts

@@ -6,7 +6,7 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import {Rule, SchematicContext, Tree} from '@angular-devkit/schematics';
+import {Rule, SchematicContext, SchematicsException, Tree} from '@angular-devkit/schematics';
 import {NodePackageInstallTask} from '@angular-devkit/schematics/tasks';
 import {WorkspaceProject} from '@schematics/angular/utility/workspace-models';
 import {sync as globSync} from 'glob';
@@ -17,6 +17,7 @@ import {MigrationCtor} from '../update-tool/migration';
 import {TargetVersion} from '../update-tool/target-version';
 import {WorkspacePath} from '../update-tool/file-system';
 import {getTargetTsconfigPath, getWorkspaceConfigGracefully} from '../utils/project-tsconfig-paths';
+import {getWorkspaceFileSystemPath} from '../utils/workspace-fs-path';
 
 import {DevkitFileSystem} from './devkit-file-system';
 import {DevkitContext, DevkitMigration, DevkitMigrationCtor} from './devkit-migration';
@@ -70,12 +71,21 @@ export function createMigrationSchematicRule(
       return;
     }
 
+    const workspaceFsPath = getWorkspaceFileSystemPath(tree);
+
+    // The workspace path could be `null` if the CLI changed the internals of the
+    // virtual file system tree. We would want users to create an issue for this
+    // if we for some reason did not catch the internal API change.
+    if (workspaceFsPath === null) {
+      throw new SchematicsException(
+        'Could not determine workspace file system path. Please report an issue ' +
+        'in the Angular Components repository with details on your Angular CLI version.');
+    }
+
     // Keep track of all project source files which have been checked/migrated. This is
     // necessary because multiple TypeScript projects can contain the same source file and
     // we don't want to check these again, as this would result in duplicated failure messages.
     const analyzedFiles = new Set<WorkspacePath>();
-    // The CLI uses the working directory as the base directory for the virtual file system tree.
-    const workspaceFsPath = process.cwd();
     const fileSystem = new DevkitFileSystem(tree, workspaceFsPath);
     const projectNames = Object.keys(workspace.projects);
     const migrations: NullableDevkitMigration[] = [...cdkMigrations, ...extraMigrations];
@@ -124,11 +134,11 @@ export function createMigrationSchematicRule(
     /** Runs the migrations for the specified workspace project. */
     function runMigrations(project: WorkspaceProject, projectName: string,
                            tsconfigPath: string, isTestTarget: boolean) {
-      const projectRootFsPath = join(workspaceFsPath, project.root);
-      const tsconfigFsPath = join(workspaceFsPath, tsconfigPath);
+      const projectRootFsPath = join(workspaceFsPath!, project.root);
+      const tsconfigFsPath = join(workspaceFsPath!, tsconfigPath);
       const program = UpdateProject.createProgramFromTsconfig(tsconfigFsPath, fileSystem);
       const updateContext: DevkitContext = {
-        workspaceFsPath,
+        workspaceFsPath: workspaceFsPath!,
         isTestTarget,
         projectName,
         project,

src/cdk/schematics/ng-update/test-cases/misc/working-directory.spec.ts

@@ -0,0 +1,30 @@
+import {join} from 'path';
+import {MIGRATION_PATH} from '../../../index.spec';
+import {createTestCaseSetup} from '../../../testing';
+
+describe('ng-update working directory', () => {
+
+  it('should migrate project if working directory is not workspace root', async () => {
+    const {runFixers, writeFile, removeTempDir, tempPath, appTree} = await createTestCaseSetup(
+      'migration-v6', MIGRATION_PATH, []);
+    const stylesheetPath = 'projects/cdk-testing/src/test-cases/global-stylesheets-test.scss';
+
+    // Write a stylesheet that will be captured by the migration.
+    writeFile(stylesheetPath, `
+      [cdkPortalHost] {
+        color: red;
+      }
+    `);
+
+    // We want to switch into a given project directory. This means that the devkit
+    // file system tree is at workspace root while the working directory is not the
+    // workspace directory as previously assumed. See the following issue for more details:
+    // https://github.com/angular/components/issues/19779
+    await runFixers(join(tempPath, 'projects/cdk-testing'));
+
+    expect(appTree.readContent(stylesheetPath)).not
+      .toContain('[cdkPortalHost]', 'Expected migration to change stylesheet contents.');
+
+    removeTempDir();
+  });
+});

src/cdk/schematics/testing/test-case-setup.ts

@@ -104,10 +104,10 @@ export async function createTestCaseSetup(migrationName: string, collectionPath:
 
   writeFile(testAppTsconfigPath, JSON.stringify(testAppTsconfig, null, 2));
 
-  const runFixers = async function() {
-    // Switch to the new temporary directory to simulate that "ng update" is ran
-    // from within the project.
-    process.chdir(tempPath);
+  const runFixers = async function(workingDir = tempPath) {
+    // Switch to the given working directory. By default, switches to the workspace
+    // root to simulate the common `ng update` usage pattern.
+    process.chdir(workingDir);
 
     // Patch "executePostTasks" to do nothing. This is necessary since
     // we cannot run the node install task in unit tests. Rather we just

src/cdk/schematics/utils/workspace-fs-path.ts

@@ -0,0 +1,30 @@
+/**
+ * @license
+ * Copyright Google LLC 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 {getSystemPath} from '@angular-devkit/core';
+import {HostDirEntry, HostTree, Tree} from '@angular-devkit/schematics';
+
+/**
+ * Gets the workspace file system path from the given tree. Returns
+ * `null` if the path could not be determined.
+ */
+// TODO: Remove this once we have a fully virtual TypeScript compiler host: COMP-387
+export function getWorkspaceFileSystemPath(tree: Tree): string|null {
+  if (!(tree.root instanceof HostDirEntry)) {
+    return null;
+  }
+  const hostTree = tree.root['_tree'];
+  if (!(hostTree instanceof HostTree) || hostTree['_backend'] === undefined) {
+    return null;
+  }
+  const backend = hostTree['_backend'];
+  if (backend['_root'] !== undefined) {
+    return getSystemPath(backend['_root']);
+  }
+  return null;
+}