fix(@schematics/angular): do not drop callThrough() on existing spies in refactor-jasmine-vitest

packages/schematics/angular/refactor/jasmine-vitest/transformers/jasmine-spy.ts

@@ -95,6 +95,19 @@ function isChainedWithAnd(node: ts.Node): boolean {
   return false;
 }
 
+function isSpyCreation(node: ts.Expression): boolean {
+  const expression = unwrapExpression(node);
+  if (!ts.isCallExpression(expression)) {
+    return false;
+  }
+
+  if (ts.isIdentifier(expression.expression)) {
+    return expression.expression.text === 'spyOn' || expression.expression.text === 'spyOnProperty';
+  }
+
+  return isJasmineCallExpression(expression, 'createSpy');
+}
+
 function transformPrimarySpy(node: ts.CallExpression, refactorCtx: RefactorContext): ts.Node {
   const { sourceFile, reporter, pendingVitestValueImports } = refactorCtx;
   if (
@@ -224,6 +237,16 @@ function transformSpyStrategy(node: ts.CallExpression, refactorCtx: RefactorCont
           newMethodName = 'mockImplementation';
           break;
         case 'callThrough':
+          if (!isSpyCreation(spyCall)) {
+            // On an existing spy, `.and.callThrough()` restores the original implementation,
+            // so it is not redundant and cannot be dropped.
+            const category = 'callThrough-on-existing-spy';
+            reporter.recordTodo(category, sourceFile, node);
+            addTodoComment(node, category);
+
+            return node;
+          }
+
           reporter.reportTransformation(
             sourceFile,
             node,

packages/schematics/angular/refactor/jasmine-vitest/transformers/jasmine-spy_spec.ts

@@ -48,6 +48,23 @@ describe('Jasmine to Vitest Transformer - transformSpies', () => {
       input: `spyOn(service, 'myMethod').and.callThrough();`,
       expected: `vi.spyOn(service, 'myMethod');`,
     },
+    {
+      description: 'should remove .and.callThrough() on a wrapped spyOn call',
+      input: `(spyOn(service, 'myMethod')!).and.callThrough();`,
+      expected: `(vi.spyOn(service, 'myMethod')!);`,
+    },
+    {
+      description: 'should add a TODO for .and.callThrough() on an existing spy',
+      input: `mySpy.and.callThrough();`,
+      expected: `// TODO: vitest-migration: Vitest does not have a direct equivalent for .and.callThrough() on an existing spy. Please migrate this manually, for example with spy.mockReset(), which restores the original implementation but also clears the recorded calls. See: https://vitest.dev/api/mock.html#mockreset
+mySpy.and.callThrough();`,
+    },
+    {
+      description: 'should add a TODO for .and.callThrough() on a spy returned by a call',
+      input: `getSpy().and.callThrough();`,
+      expected: `// TODO: vitest-migration: Vitest does not have a direct equivalent for .and.callThrough() on an existing spy. Please migrate this manually, for example with spy.mockReset(), which restores the original implementation but also clears the recorded calls. See: https://vitest.dev/api/mock.html#mockreset
+getSpy().and.callThrough();`,
+    },
     {
       description: 'should transform jasmine.createSpy("name") to vi.fn().mockName("name")',
       input: `const mySpy = jasmine.createSpy('mySpy');`,

packages/schematics/angular/refactor/jasmine-vitest/utils/todo-notes.ts

@@ -158,6 +158,13 @@ export const TODO_NOTES = {
       `Unsupported spy strategy ".and.${context.name}()" found. Please migrate this manually.`,
     url: 'https://vitest.dev/api/mocked.html#mock',
   },
+  'callThrough-on-existing-spy': {
+    message:
+      'Vitest does not have a direct equivalent for .and.callThrough() on an existing spy.' +
+      ' Please migrate this manually, for example with spy.mockReset(), which restores' +
+      ' the original implementation but also clears the recorded calls.',
+    url: 'https://vitest.dev/api/mock.html#mockreset',
+  },
   'mostRecent-without-args': {
     message:
       'Direct usage of mostRecent() is not supported.' +