feat(material/schematics): initial setup for template migrations (#24515)

* feat(material/schematics): initial setup for template migrations

* created TemplateMigration for migrating templates
* added it to the migrations for the mdc-migration schematic

Author: wagnermaciel

src/material/schematics/ng-generate/mdc-migration/BUILD.bazel

@@ -16,6 +16,7 @@ ts_library(
     deps = [
         "//src/cdk/schematics",
         "@npm//@angular-devkit/schematics",
+        "@npm//@angular/compiler",
         "@npm//@types/node",
         "@npm//postcss",
         "@npm//postcss-scss",

src/material/schematics/ng-generate/mdc-migration/index.ts

@@ -10,6 +10,7 @@ import {Rule, SchematicContext, Tree} from '@angular-devkit/schematics';
 import {Schema} from './schema';
 import {DevkitFileSystem, UpdateProject, findStylesheetFiles} from '@angular/cdk/schematics';
 import {ThemingStylesMigration} from './rules/theming-styles';
+import {TemplateMigration} from './rules/template-migration';
 import {MIGRATORS} from './rules';
 import {dirname} from 'path';
 import {StyleMigrator} from './rules/style-migrator';
@@ -78,7 +79,7 @@ export default function (options: Schema): Rule {
     const additionalStylesheetPaths = findStylesheetFiles(tree, migrationDir);
     const project = new UpdateProject(context, program, fileSystem, new Set(), context.logger);
     const {hasFailures} = project.migrate(
-      [ThemingStylesMigration],
+      [ThemingStylesMigration, TemplateMigration],
       null,
       migrators,
       additionalStylesheetPaths,

src/material/schematics/ng-generate/mdc-migration/rules/components/test-setup-helper.ts

@@ -12,6 +12,7 @@ import {runfiles} from '@bazel/runfiles';
 const TS_CONFIG = '/projects/material/tsconfig.app.json';
 
 export const THEME_FILE = '/projects/material/src/theme.scss';
+export const TEMPLATE_FILE = '/projects/material/src/app/app.component.html';
 
 export function createNewTestRunner(): SchematicTestRunner {
   return new SchematicTestRunner(

src/material/schematics/ng-generate/mdc-migration/rules/template-migration.spec.ts

@@ -0,0 +1,23 @@
+import {createTestApp, patchDevkitTreeToExposeTypeScript} from '@angular/cdk/schematics/testing';
+import {SchematicTestRunner, UnitTestTree} from '@angular-devkit/schematics/testing';
+import {createNewTestRunner, migrateComponent, TEMPLATE_FILE} from './components/test-setup-helper';
+
+describe('template migrations', () => {
+  let runner: SchematicTestRunner;
+  let cliAppTree: UnitTestTree;
+
+  async function runMigrationTest(oldFileContent: string, newFileContent: string) {
+    cliAppTree.overwrite(TEMPLATE_FILE, oldFileContent);
+    const tree = await migrateComponent('card', runner, cliAppTree);
+    expect(tree.readContent(TEMPLATE_FILE)).toBe(newFileContent);
+  }
+
+  beforeEach(async () => {
+    runner = createNewTestRunner();
+    cliAppTree = patchDevkitTreeToExposeTypeScript(await createTestApp(runner));
+  });
+
+  it('should do nothing yet', async () => {
+    await runMigrationTest('<h1>Hello</h1>', '<h1>Hello</h1>');
+  });
+});

src/material/schematics/ng-generate/mdc-migration/rules/template-migration.ts

@@ -0,0 +1,56 @@
+/**
+ * @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 {Migration, ResolvedResource} from '@angular/cdk/schematics';
+import {SchematicContext} from '@angular-devkit/schematics';
+import {StyleMigrator} from './style-migrator';
+import * as compiler from '@angular/compiler';
+
+/**
+ * Traverses the given tree of nodes and runs the given callbacks for each Element node encountered.
+ *
+ * Note that updates to the start tags of html element should be done in the postorder callback,
+ * and updates to the end tags of html elements should be done in the preorder callback to avoid
+ * issues with line collisions.
+ *
+ * @param nodes The nodes of the ast from a parsed template.
+ * @param preorderCallback A function that gets run for each Element node in a preorder traversal.
+ * @param postorderCallback A function that gets run for each Element node in a postorder traversal.
+ */
+function visitElements(
+  nodes: compiler.TmplAstNode[],
+  preorderCallback: (node: compiler.TmplAstElement) => void = () => {},
+  postorderCallback: (node: compiler.TmplAstElement) => void = () => {},
+): void {
+  for (let i = 0; i < nodes.length; i++) {
+    const node = nodes[i];
+    if (node instanceof compiler.TmplAstElement) {
+      preorderCallback(node);
+      visitElements(node.children, preorderCallback, postorderCallback);
+      postorderCallback(node);
+    }
+  }
+}
+
+export class TemplateMigration extends Migration<StyleMigrator[], SchematicContext> {
+  enabled = true;
+
+  override visitTemplate(template: ResolvedResource) {
+    const ast = compiler.parseTemplate(template.content, template.filePath, {
+      preserveWhitespaces: true,
+      preserveLineEndings: true,
+      leadingTriviaChars: [],
+    });
+
+    visitElements(ast.nodes, node => {
+      // TODO(wagnermaciel): implement the migration updates.
+    });
+
+    this.fileSystem.overwrite(template.filePath, template.content);
+  }
+}