feat(material/icon): Change icon font default to Material symbols from Material icons

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

@@ -6,25 +6,72 @@
  * found in the LICENSE file at https://angular.dev/license
  */
 
-import {Rule, SchematicContext} from '@angular-devkit/schematics';
+import {chain, Rule, SchematicContext, Tree} from '@angular-devkit/schematics';
 import {
+  appendHtmlElementToHead,
   createMigrationSchematicRule,
+  getProjectFromWorkspace,
+  getProjectIndexFiles,
+  getWorkspaceConfigGracefully,
   NullableDevkitMigration,
   TargetVersion,
 } from '@angular/cdk/schematics';
+import {getWorkspace} from '@schematics/angular/utility/workspace';
 
 import {materialUpgradeData} from './upgrade-data';
 
 const materialMigrations: NullableDevkitMigration[] = [];
 
 /** Entry point for the migration schematics with target of Angular Material v20 */
 export function updateToV20(): Rule {
-  return createMigrationSchematicRule(
-    TargetVersion.V20,
-    materialMigrations,
-    materialUpgradeData,
-    onMigrationComplete,
-  );
+  return chain([
+    createMigrationSchematicRule(
+      TargetVersion.V20,
+      materialMigrations,
+      materialUpgradeData,
+      onMigrationComplete,
+    ),
+    // Updating to the new Material Symbols isn't a migration within materialMigrations since
+    // the index files are never visited within the migration schematic rule. The
+    // migrate() function within the update-tool only visits files referenced in
+    // typescript files which excludes the index template files:
+    // https://github.com/angular/components/blob/main/src/cdk/schematics/update-tool/index.ts#L71.
+    updateIconFontToMaterialSymbolsRule(),
+  ]);
+}
+
+/**
+ * Finds the index files and adds the import for Material Symbols font if needed. As of v20,
+ * Material Symbols becomes the default font icon since Material Icons is deprecated. This
+ * rule ensures the Material Symbols font is imported for existing applications.
+ * @returns Rule that adds the import for the Material Symbols icon font to the index files
+ */
+function updateIconFontToMaterialSymbolsRule(): Rule {
+  return async (tree: Tree, context: SchematicContext) => {
+    const workspace = await getWorkspaceConfigGracefully(tree);
+    const projectNames = workspace!.projects.keys();
+
+    let indexFiles: string[] = [];
+    for (const projectName of projectNames) {
+      const project = getProjectFromWorkspace(await getWorkspace(tree), projectName);
+      indexFiles = [...indexFiles, ...getProjectIndexFiles(project)];
+    }
+
+    const materialSymbolsFont =
+      'https://fonts.googleapis.com/icon?family=Material+Symbols+Outlined';
+    for (const indexFile of indexFiles) {
+      // Add Material Symbols font if not imported in index file. References to the deprecated
+      // Material Icons are not removed since some applications may have manual overrides in their
+      // component styles that still reference it.
+      if (!tree.read(indexFile)?.includes(materialSymbolsFont)) {
+        appendHtmlElementToHead(
+          tree,
+          indexFile,
+          `<link href="${materialSymbolsFont}" rel="stylesheet">`,
+        );
+      }
+    }
+  };
 }
 
 /** Function that will be called when the migration completed. */

src/material/schematics/ng-update/test-cases/v20-mat-symbols-icon-font.spec.ts

@@ -0,0 +1,87 @@
+import {UnitTestTree} from '@angular-devkit/schematics/testing';
+import {createTestCaseSetup} from '@angular/cdk/schematics/testing';
+import {MIGRATION_PATH} from '../../paths';
+
+const INDEX_HTML_FILE_PATH = '/projects/cdk-testing/src/index.html';
+
+describe('v20 material symbols icon font migration', () => {
+  let tree: UnitTestTree;
+  let writeFile: (filename: string, content: string) => void;
+  let runMigration: () => Promise<unknown>;
+
+  function stripWhitespace(content: string): string {
+    return content.replace(/\s/g, '');
+  }
+
+  beforeEach(async () => {
+    const testSetup = await createTestCaseSetup('migration-v20', MIGRATION_PATH, []);
+    tree = testSetup.appTree;
+    writeFile = testSetup.writeFile;
+    runMigration = testSetup.runFixers;
+  });
+
+  it('should add Material Symbols font to index html file', async () => {
+    writeFile(
+      INDEX_HTML_FILE_PATH,
+      `
+        <!doctype html>
+        <html lang="en">
+          <head>
+            <link rel="preconnect" href="https://fonts.gstatic.com">
+            <link href="https://fonts.googleapis.com/icon?family=Material+Icons" rel="stylesheet">
+          </head>
+          <body></body>
+        </html>
+      `,
+    );
+
+    await runMigration();
+
+    expect(stripWhitespace(tree.readText(INDEX_HTML_FILE_PATH))).toBe(
+      stripWhitespace(`
+        <!doctype html>
+        <html lang="en">
+          <head>
+            <link rel="preconnect" href="https://fonts.gstatic.com">
+            <link href="https://fonts.googleapis.com/icon?family=Material+Icons" rel="stylesheet">
+            <link href="https://fonts.googleapis.com/icon?family=Material+Symbols+Outlined" rel="stylesheet">
+          </head>
+          <body></body>
+        </html>
+    `),
+    );
+  });
+
+  it('should not add Material Symbols font to index html file if it is already imported', async () => {
+    writeFile(
+      INDEX_HTML_FILE_PATH,
+      `
+        <!doctype html>
+        <html lang="en">
+          <head>
+            <link rel="preconnect" href="https://fonts.gstatic.com">
+            <link href="https://fonts.googleapis.com/icon?family=Material+Icons" rel="stylesheet">
+            <link href="https://fonts.googleapis.com/icon?family=Material+Symbols+Outlined" rel="stylesheet">
+          </head>
+          <body></body>
+        </html>
+      `,
+    );
+
+    await runMigration();
+
+    expect(stripWhitespace(tree.readText(INDEX_HTML_FILE_PATH))).toBe(
+      stripWhitespace(`
+        <!doctype html>
+        <html lang="en">
+          <head>
+            <link rel="preconnect" href="https://fonts.gstatic.com">
+            <link href="https://fonts.googleapis.com/icon?family=Material+Icons" rel="stylesheet">
+            <link href="https://fonts.googleapis.com/icon?family=Material+Symbols+Outlined" rel="stylesheet">
+          </head>
+          <body></body>
+        </html>
+    `),
+    );
+  });
+});