fix(material/core): prevent updates to v17 if project uses legacy components

These changes add a schematic that will log a fatal error and prevent the app from updating to v17 if it's using legacy components. Legacy components have been deleted in v17 so the app won't build if it updates.

Author: crisbeto

guides/v15-mdc-migration.md

@@ -1,6 +1,6 @@
 # Migrating to MDC-based Angular Material Components
 
-In Angular Material v15, many of the components have been refactored to be based on the official
+In Angular Material v15 and later, many of the components have been refactored to be based on the official
 [Material Design Components for Web (MDC)](https://github.com/material-components/material-components-web).
 The components from the following imports have been refactored:
 
@@ -81,22 +81,22 @@ practices before migrating.
   component. Using component harnesses makes your tests easier to understand and more robust to
   changes in Angular Material
 
-### 1. Update to Angular Material v15
+### 1. Update to Angular Material v16
 
 Angular Material includes a schematic to help migrate applications to use the new MDC-based
-components. To get started, upgrade your application to Angular Material 15.
+components. To get started, upgrade your application to Angular Material 16.
 
 ```shell
-ng update @angular/material@15
+ng update @angular/material@16
 ```
 
 As part of this update, a schematic will run to automatically move your application to use the
 "legacy" imports containing the old component implementations. This provides a quick path to getting
-your application running on v15 with minimal manual changes.
+your application running on v16 with minimal manual changes.
 
 ### 2. Run the migration tool
 
-After upgrading to v15, you can run the migration tool to switch from the legacy component
+After upgrading to v16, you can run the migration tool to switch from the legacy component
 implementations to the new MDC-based ones.
 
 ```shell

src/material/schematics/migration.json

@@ -3,7 +3,7 @@
   "schematics": {
     "migration-v17": {
       "version": "17.0.0-0",
-      "description": "Updates the Angular Material to v17",
+      "description": "Updates Angular Material to v17",
       "factory": "./ng-update/index_bundled#updateToV17"
     }
   }

src/material/schematics/ng-update/BUILD.bazel

@@ -69,6 +69,7 @@ ts_library(
         "//src/cdk/schematics",
         "//src/cdk/schematics/testing",
         "//src/material/schematics:paths",
+        "@npm//@angular-devkit/core",
         "@npm//@angular-devkit/schematics",
         "@npm//@bazel/runfiles",
         "@npm//@types/jasmine",

src/material/schematics/ng-update/index.ts

@@ -13,18 +13,24 @@ import {
   TargetVersion,
 } from '@angular/cdk/schematics';
 
+import {legacyImportsError} from './migrations/legacy-imports-error';
 import {materialUpgradeData} from './upgrade-data';
 import {ThemeBaseMigration} from './migrations/theme-base-v17';
 
 const materialMigrations: NullableDevkitMigration[] = [ThemeBaseMigration];
 
 /** Entry point for the migration schematics with target of Angular Material v17 */
 export function updateToV17(): Rule {
-  return createMigrationSchematicRule(
-    TargetVersion.V17,
-    materialMigrations,
-    materialUpgradeData,
-    onMigrationComplete,
+  // We pass the v17 migration rule as a callback, instead of using `chain()`, because the
+  // legacy imports error only logs an error message, it doesn't actually interrupt the migration
+  // process and we don't want to execute migrations if there are leftover legacy imports.
+  return legacyImportsError(
+    createMigrationSchematicRule(
+      TargetVersion.V17,
+      materialMigrations,
+      materialUpgradeData,
+      onMigrationComplete,
+    ),
   );
 }
 

src/material/schematics/ng-update/migrations/legacy-imports-error.ts

@@ -0,0 +1,81 @@
+/**
+ * @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 {Rule, SchematicContext, Tree} from '@angular-devkit/schematics';
+import {NodePackageInstallTask} from '@angular-devkit/schematics/tasks';
+import * as ts from 'typescript';
+
+/**
+ * "Migration" that logs an error and prevents further migrations
+ * from running if the project is using legacy components.
+ * @param onSuccess Rule to run if there are no legacy imports.
+ */
+export function legacyImportsError(onSuccess: Rule): Rule {
+  return async (tree: Tree, context: SchematicContext) => {
+    const filesUsingLegacyImports = new Set<string>();
+
+    tree.visit(path => {
+      if (!path.endsWith('.ts')) {
+        return;
+      }
+
+      const content = tree.readText(path);
+      const sourceFile = ts.createSourceFile(path, content, ts.ScriptTarget.Latest);
+
+      sourceFile.forEachChild(function walk(node) {
+        const isImportOrExport = ts.isImportDeclaration(node) || ts.isExportDeclaration(node);
+
+        if (
+          isImportOrExport &&
+          node.moduleSpecifier &&
+          ts.isStringLiteralLike(node.moduleSpecifier) &&
+          node.moduleSpecifier.text.startsWith('@angular/material/legacy-')
+        ) {
+          filesUsingLegacyImports.add(path);
+        }
+
+        node.forEachChild(walk);
+      });
+    });
+
+    // If there are no legacy imports left, we can continue with the migrations.
+    if (filesUsingLegacyImports.size === 0) {
+      return onSuccess;
+    }
+
+    // At this point the project is already at v17 so we need to downgrade it back
+    // to v16 and run `npm install` again. Ideally we would also throw an error here
+    // to interrupt the update process, but that would interrupt `npm install` as well.
+    if (tree.exists('package.json')) {
+      let packageJson: Record<string, any> | null = null;
+
+      try {
+        packageJson = JSON.parse(tree.readText('package.json')) as Record<string, any>;
+      } catch {}
+
+      if (packageJson !== null && packageJson['dependencies']) {
+        packageJson['dependencies']['@angular/material'] = '^16.2.0';
+        tree.overwrite('package.json', JSON.stringify(packageJson, null, 2));
+        context.addTask(new NodePackageInstallTask());
+      }
+    }
+
+    const errorMessage =
+      `Cannot update to Angular Material v17, because the project is using the legacy ` +
+      `Material components\nthat have been deleted. While Angular Material v16 is compatible with ` +
+      `Angular v17, it is recommended\nto switch away from the legacy components as soon as possible, ` +
+      `because they no longer receive bug fixes,\naccessibility improvements and new features.\n\n` +
+      `Read more about migrating away from legacy components: https://material.angular.io/guide/mdc-migration\n\n` +
+      `Files in the project using legacy Material components:\n` +
+      Array.from(filesUsingLegacyImports, path => ' - ' + path).join('\n') +
+      '\n';
+
+    context.logger.fatal(errorMessage);
+    return;
+  };
+}

src/material/schematics/ng-update/test-cases/legacy-imports-error.spec.ts

@@ -0,0 +1,83 @@
+import {createTestCaseSetup} from '@angular/cdk/schematics/testing';
+import {UnitTestTree} from '@angular-devkit/schematics/testing';
+import {logging} from '@angular-devkit/core';
+import {MIGRATION_PATH} from '../../paths';
+
+describe('legacy imports error', () => {
+  const PATH = 'projects/material-testing/';
+  let runFixers: () => Promise<unknown>;
+  let tree: UnitTestTree;
+  let writeFile: (path: string, content: string) => void;
+  let fatalLogs: string[];
+
+  beforeEach(async () => {
+    const setup = await createTestCaseSetup('migration-v17', MIGRATION_PATH, []);
+    runFixers = setup.runFixers;
+    writeFile = setup.writeFile;
+    tree = setup.appTree;
+    fatalLogs = [];
+    setup.runner.logger.subscribe((entry: logging.LogEntry) => {
+      if (entry.level === 'fatal') {
+        fatalLogs.push(entry.message);
+      }
+    });
+  });
+
+  afterEach(() => {
+    runFixers = tree = writeFile = fatalLogs = null!;
+  });
+
+  it('should log a fatal message if the app imports a legacy import', async () => {
+    writeFile(
+      `${PATH}/src/app/app.module.ts`,
+      `
+      import {NgModule} from '@angular/core';
+      import {MatLegacyButtonModule} from '@angular/material/legacy-button';
+
+      @NgModule({
+        imports: [MatLegacyButtonModule],
+      })
+      export class AppModule {}
+    `,
+    );
+
+    await runFixers();
+
+    expect(fatalLogs.length).toBe(1);
+    expect(fatalLogs[0]).toContain(
+      'Cannot update to Angular Material v17, ' +
+        'because the project is using the legacy Material components',
+    );
+  });
+
+  it('should downgrade the app to v16 if it contains legacy imports', async () => {
+    writeFile(
+      `${PATH}/package.json`,
+      `{
+        "name": "test",
+        "version": "0.0.0",
+        "dependencies": {
+          "@angular/material": "^17.0.0"
+        }
+      }`,
+    );
+
+    writeFile(
+      `${PATH}/src/app/app.module.ts`,
+      `
+      import {NgModule} from '@angular/core';
+      import {MatLegacyButtonModule} from '@angular/material/legacy-button';
+
+      @NgModule({
+        imports: [MatLegacyButtonModule],
+      })
+      export class AppModule {}
+    `,
+    );
+
+    await runFixers();
+
+    const content = JSON.parse(tree.readText('/package.json')) as Record<string, any>;
+    expect(content['dependencies']['@angular/material']).toBe('^16.2.0');
+  });
+});