fix(material/schematics): not migrating elements with template direct…

…ives

The MDC migration wasn't traversing into template elements which meant that it wouldn't migrate elements with an `*ngIf` or an `*ngFor` on them.

Fixes #25824.

integration/mdc-migration/golden/src/app/components/chips/chips.component.html

@@ -15,12 +15,12 @@ <h2>Chips example</h2>
 <mat-form-field class="example-chip-list" appearance="fill">
     <mat-label>Favorite Fruits</mat-label>
     <mat-chip-grid #fruitChipList aria-label="Fruit selection">
-        <mat-chip *ngFor="let fruit of fruits" (removed)="remove(fruit)">
+        <mat-chip-row *ngFor="let fruit of fruits" (removed)="remove(fruit)">
             {{fruit.name}}
             <button matChipRemove>
                 <mat-icon>cancel</mat-icon>
             </button>
-        </mat-chip>
+        </mat-chip-row>
         <input placeholder="New fruit..."
             [matChipInputFor]="fruitChipList"
             [matChipInputSeparatorKeyCodes]="separatorKeysCodes"

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

@@ -93,4 +93,66 @@ describe('chips template migrator', () => {
   it('should update standalone chips', async () => {
     await runMigrationTest('<mat-chip></mat-chip>', '<mat-chip-option></mat-chip-option>');
   });
+
+  it('should update mat-chip with an *ngFor', async () => {
+    await runMigrationTest(
+      `
+        <mat-chip-list>
+          <mat-chip *ngFor="let chip of chips">{{chip}}</mat-chip>
+        </mat-chip-list>
+      `,
+      `
+        <mat-chip-listbox>
+          <mat-chip-option *ngFor="let chip of chips">{{chip}}</mat-chip-option>
+        </mat-chip-listbox>
+      `,
+    );
+  });
+
+  it('should update a chip listbox with a nested ng-container', async () => {
+    await runMigrationTest(
+      `
+        <mat-chip-list>
+          <ng-container *ngFor="let category of categories">
+            <ng-container *ngIf="category === 'something'">
+              <mat-chip *ngFor="let chip of category.chips" [selectable]="false">{{chip}}</mat-chip>
+            </ng-container>
+          </ng-container>
+        </mat-chip-list>
+      `,
+      `
+        <mat-chip-listbox>
+          <ng-container *ngFor="let category of categories">
+            <ng-container *ngIf="category === 'something'">
+              <mat-chip-option *ngFor="let chip of category.chips" [selectable]="false">{{chip}}</mat-chip-option>
+            </ng-container>
+          </ng-container>
+        </mat-chip-listbox>
+      `,
+    );
+  });
+
+  it('should update a chip with an *ngIf', async () => {
+    await runMigrationTest(
+      '<mat-chip *ngIf="isShown"></mat-chip>',
+      '<mat-chip-option *ngIf="isShown"></mat-chip-option>',
+    );
+  });
+
+  it('should update a chip grid with an *ngFor', async () => {
+    await runMigrationTest(
+      `
+        <mat-chip-list #chipList>
+          <mat-chip *ngFor="let chip of chips">{{chip}}</mat-chip>
+          <input type="text" matInput [matChipInputFor]="chipList">
+        </mat-chip-list>
+      `,
+      `
+        <mat-chip-grid #chipList>
+          <mat-chip-row *ngFor="let chip of chips">{{chip}}</mat-chip-row>
+          <input type="text" matInput [matChipInputFor]="chipList">
+        </mat-chip-grid>
+      `,
+    );
+  });
 });

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

@@ -48,6 +48,49 @@ function runClearAttributeTest(html: string, result: string): void {
 }
 
 describe('#visitElements', () => {
+  describe('visitElements', () => {
+    it('should traverse elements with an *ngFor', () => {
+      const visitedElements: string[] = [];
+      const template = `
+        <parent>
+          <child *ngFor="let c of children">
+            <grandchild *ngFor="let g of c.children"></grandchild>
+          </child>
+        </parent>
+      `;
+
+      visitElements(parseTemplate(template).nodes, node => visitedElements.push(node.name));
+      expect(visitedElements).toEqual(['parent', 'child', 'grandchild']);
+    });
+
+    it('should traverse elements inside ng-container', () => {
+      const visitedElements: string[] = [];
+      const template = `
+        <ng-container>
+          <parent>
+            <ng-container>
+              <child>
+                <ng-container>
+                  <grandchild></grandchild>
+                </ng-container>
+              </child>
+            </ng-container>
+          </parent>
+        </ng-container>
+      `;
+
+      visitElements(parseTemplate(template).nodes, node => visitedElements.push(node.name));
+      expect(visitedElements).toEqual([
+        'ng-container',
+        'parent',
+        'ng-container',
+        'child',
+        'ng-container',
+        'grandchild',
+      ]);
+    });
+  });
+
   describe('tag name replacements', () => {
     it('should handle basic cases', async () => {
       runTagNameDuplicationTest('<a></a>', '<aa></aa>');

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

@@ -10,6 +10,7 @@ import {
   ParsedTemplate,
   TmplAstElement,
   TmplAstNode,
+  TmplAstTemplate,
   parseTemplate as parseTemplateUsingCompiler,
 } from '@angular/compiler';
 
@@ -32,9 +33,18 @@ export function visitElements(
   nodes.reverse();
   for (let i = 0; i < nodes.length; i++) {
     const node = nodes[i];
-    if (node instanceof TmplAstElement) {
+    const isElement = node instanceof TmplAstElement;
+
+    if (isElement) {
       preorderCallback(node);
+    }
+
+    // Descend both into elements and templates in order to cover cases like `*ngIf` and `*ngFor`.
+    if (isElement || node instanceof TmplAstTemplate) {
       visitElements(node.children, preorderCallback, postorderCallback);
+    }
+
+    if (isElement) {
       postorderCallback(node);
     }
   }
@@ -46,8 +56,8 @@ export function visitElements(
  *
  * For more details, see https://github.com/angular/angular/blob/4332897baa2226ef246ee054fdd5254e3c129109/packages/compiler-cli/src/ngtsc/annotations/component/src/resources.ts#L230.
  *
- * @param html text of the template to parse
- * @param filePath URL to use for source mapping of the parsed template
+ * @param template text of the template to parse
+ * @param templateUrl URL to use for source mapping of the parsed template
  * @returns the updated template html.
  */
 export function parseTemplate(template: string, templateUrl: string = ''): ParsedTemplate {