fix(@schematics/angular): only run emitDecoratorMetadata removal migration in safe workspaces

Removal of `emitDecoratorMetadata` might cause runtime errors on projects which don't use the Angular Compiler to compile TypeScript code and therefore dependent on Decorators metadata during runtime.  One such example of these builders is `@nrwl/jest`.

(cherry picked from commit 7521a87)

Author: alan-agius4

packages/schematics/angular/migrations/update-12/remove-emit-decorator-metadata.ts

@@ -9,6 +9,7 @@
 import { join } from '@angular-devkit/core';
 import { DirEntry, Rule } from '@angular-devkit/schematics';
 import { JSONFile } from '../../utility/json-file';
+import { allWorkspaceTargets, getWorkspace } from '../../utility/workspace';
 
 function* visitJsonFiles(directory: DirEntry): IterableIterator<string> {
   for (const path of directory.subfiles) {
@@ -29,7 +30,26 @@ function* visitJsonFiles(directory: DirEntry): IterableIterator<string> {
 }
 
 export default function (): Rule {
-  return (tree) => {
+  return async (tree, { logger }) => {
+    const workspace = await getWorkspace(tree);
+    const hasThirdPartyBuilders = [...allWorkspaceTargets(workspace)].some(([, target]) => {
+      const { builder } = target;
+
+      return !(
+        builder.startsWith('@angular-devkit/build-angular') ||
+        builder.startsWith('@nguniversal/builders')
+      );
+    });
+
+    if (hasThirdPartyBuilders) {
+      logger.warn(
+        'Skipping migration as the workspace uses third-party builders which may ' +
+          'require "emitDecoratorMetadata" TypeScript compiler option.',
+      );
+
+      return;
+    }
+
     for (const path of visitJsonFiles(tree.root)) {
       const content = tree.read(path);
       if (content?.toString().includes('"emitDecoratorMetadata"')) {

packages/schematics/angular/migrations/update-12/remove-emit-decorator-metadata_spec.ts

@@ -9,6 +9,7 @@
 import { EmptyTree } from '@angular-devkit/schematics';
 import { SchematicTestRunner, UnitTestTree } from '@angular-devkit/schematics/testing';
 import { parse as parseJson } from 'jsonc-parser';
+import { Builders } from '../../utility/workspace-models';
 
 describe('Migration to remove "emitDecoratorMetadata" compiler option', () => {
   const schematicName = 'remove-emit-decorator-metadata';
@@ -26,6 +27,28 @@ describe('Migration to remove "emitDecoratorMetadata" compiler option', () => {
   let tree: UnitTestTree;
   beforeEach(() => {
     tree = new UnitTestTree(new EmptyTree());
+    tree.create(
+      '/angular.json',
+      JSON.stringify(
+        {
+          version: 1,
+          projects: {
+            app: {
+              root: '',
+              sourceRoot: 'src',
+              prefix: 'app',
+              architect: {
+                browser: {
+                  builder: Builders.Browser,
+                },
+              },
+            },
+          },
+        },
+        undefined,
+        2,
+      ),
+    );
   });
 
   it(`should rename 'emitDecoratorMetadata' when set to false`, async () => {
@@ -88,4 +111,45 @@ describe('Migration to remove "emitDecoratorMetadata" compiler option', () => {
     const { options } = readJsonFile(newTree, '/foo.json');
     expect(options['emitDecoratorMetadata']).toBeTrue();
   });
+
+  it(`should not remove 'emitDecoratorMetadata' when one of the builders is a third-party`, async () => {
+    tree.create(
+      '/tsconfig.json',
+      JSON.stringify(
+        {
+          compilerOptions: {
+            emitDecoratorMetadata: true,
+            strict: true,
+          },
+        },
+        undefined,
+        2,
+      ),
+    );
+    tree.overwrite(
+      '/angular.json',
+      JSON.stringify(
+        {
+          version: 1,
+          projects: {
+            app: {
+              root: '',
+              sourceRoot: 'src',
+              prefix: 'app',
+              architect: {
+                browser: {
+                  builder: '@nrwl/jest',
+                },
+              },
+            },
+          },
+        },
+        undefined,
+        2,
+      ),
+    );
+    const newTree = await schematicRunner.runSchematicAsync(schematicName, {}, tree).toPromise();
+    const { compilerOptions } = readJsonFile(newTree, '/tsconfig.json');
+    expect(compilerOptions['emitDecoratorMetadata']).toBeTrue();
+  });
 });