feat(@schematics/angular): migrate fakeAsync's flush behavior when used in beforeEach

Author: yjaaidi

packages/schematics/angular/refactor/jasmine-vitest/transformers/fake-async-test.ts

@@ -107,13 +107,30 @@ function _transformFakeAsyncCall(
     `Transformed \`fakeAsync\` to \`vi.useFakeTimers\`.`,
   );
 
+  let statements = callbackBody.statements;
+
+  // Append `vi.runOnlyPendingTimersAsync()` as the last statement of `beforeEach` to mimic flush behavior.
+  if (
+    ts.isCallExpression(node.parent) &&
+    ts.isIdentifier(node.parent.expression) &&
+    node.parent.expression.text === 'beforeEach' &&
+    !_isFakeAsyncFlushDisabled(node)
+  ) {
+    statements = ts.factory.createNodeArray([
+      ...statements,
+      ts.factory.createExpressionStatement(
+        ts.factory.createAwaitExpression(createViCallExpression(ctx, 'runOnlyPendingTimersAsync')),
+      ),
+    ]);
+  }
+
   return ts.factory.createArrowFunction(
     [ts.factory.createModifier(ts.SyntaxKind.AsyncKeyword)],
     fakeAsyncCallback.typeParameters,
     fakeAsyncCallback.parameters,
     undefined,
     ts.factory.createToken(ts.SyntaxKind.EqualsGreaterThanToken),
-    ts.factory.createBlock(callbackBody.statements),
+    ts.factory.createBlock(statements),
   );
 }
 
@@ -177,6 +194,25 @@ function _createFakeTimersHookStatements(ctx: RefactorContext): ts.Statement[] {
   ];
 }
 
+/**
+ * Detects if the `flush` option is set to false in the `fakeAsync` call expression.
+ * e.g. `fakeAsync(() => { ... }, { flush: false })`
+ */
+function _isFakeAsyncFlushDisabled(fakeAsyncCallExpression: ts.CallExpression): boolean {
+  const options = fakeAsyncCallExpression.arguments[1];
+
+  return (
+    options &&
+    ts.isObjectLiteralExpression(options) &&
+    options.properties.some(
+      (property) =>
+        ts.isPropertyAssignment(property) &&
+        property.name.getText() === 'flush' &&
+        property.initializer.getText() === 'false',
+    )
+  );
+}
+
 interface CurrentOutermostDescribeContext {
   isUsingFakeAsync: boolean;
 }

packages/schematics/angular/refactor/jasmine-vitest/transformers/fake-async-test_spec.ts

@@ -154,28 +154,79 @@ describe('transformFakeAsyncTest', () => {
     },
     {
       description:
-        'should transform fakeAsync test to `vi.useFakeTimers()` in `beforeEach`, `afterEach`, `beforeAll`, `afterAll`',
+        'should transform fakeAsync test to `vi.useFakeTimers()` in `beforeEach` and preserve flush behavior',
       input: `
           import { fakeAsync } from '@angular/core/testing';
 
           describe('My fakeAsync suite', () => {
-            beforeAll(fakeAsync(() => {
-              console.log('beforeAll');
+          
+            let count = 0;
+            beforeEach(fakeAsync(() => {
+              setTimeout(() => ++count, 100);
             }));
 
-            afterAll(fakeAsync(() => {
-              console.log('afterAll');
+            it('works', fakeAsync(() => {
+              expect(count).toBe(1);
             }));
+          });
+      `,
+      expected: `
+          describe('My fakeAsync suite', () => {
+            beforeEach(() => {
+              vi.useFakeTimers({ advanceTimeDelta: 1, shouldAdvanceTime: true });
+            });
+            afterEach(() => {
+              vi.useRealTimers();
+            });
 
-            beforeEach(fakeAsync(() => {
-              console.log('beforeEach');
-            }));
+            let count = 0;
+            beforeEach(async () => {
+              setTimeout(() => ++count, 100);
+              await vi.runOnlyPendingTimersAsync();
+            });
+
+            it('works', async () => {
+              expect(count).toBe(1);
+            });
+          });
+      `,
+    },
+    {
+      description: 'should transform fakeAsync test to `vi.useFakeTimers()` in `afterEach`',
+      input: `
+          import { fakeAsync } from '@angular/core/testing';
 
+          describe('My fakeAsync suite', () => {
             afterEach(fakeAsync(() => {
               console.log('afterEach');
             }));
           });
         `,
+      expected: `
+          describe('My fakeAsync suite', () => {
+            beforeEach(() => {
+              vi.useFakeTimers({ advanceTimeDelta: 1, shouldAdvanceTime: true });
+            });
+            afterEach(() => {
+              vi.useRealTimers();
+            });
+            afterEach(async () => {
+              console.log('afterEach');
+            });
+          });
+        `,
+    },
+    {
+      description: 'should transform fakeAsync test to `vi.useFakeTimers()` in `beforeAll`',
+      input: `
+          import { fakeAsync } from '@angular/core/testing';
+
+          describe('My fakeAsync suite', () => {
+            beforeAll(fakeAsync(() => {
+              console.log('beforeAll');
+            }));
+          });
+        `,
       expected: `
           describe('My fakeAsync suite', () => {
             beforeEach(() => {
@@ -187,17 +238,30 @@ describe('transformFakeAsyncTest', () => {
             beforeAll(async () => {
               console.log('beforeAll');
             });
+          });
+        `,
+    },
+    {
+      description: 'should transform fakeAsync test to `vi.useFakeTimers()` in `afterAll`',
+      input: `
+          import { fakeAsync } from '@angular/core/testing';
 
-            afterAll(async () => {
+          describe('My fakeAsync suite', () => {
+            afterAll(fakeAsync(() => {
               console.log('afterAll');
+            }));
+          });
+        `,
+      expected: `
+          describe('My fakeAsync suite', () => {
+            beforeEach(() => {
+              vi.useFakeTimers({ advanceTimeDelta: 1, shouldAdvanceTime: true });
             });
-
-            beforeEach(async () => {
-              console.log('beforeEach');
+            afterEach(() => {
+              vi.useRealTimers();
             });
-
-            afterEach(async () => {
-              console.log('afterEach');
+            afterAll(async () => {
+              console.log('afterAll');
             });
           });
         `,
@@ -240,6 +304,65 @@ describe('transformFakeAsyncTest', () => {
           });
         `,
     },
+    {
+      description: 'should not append `vi.runOnlyPendingTimersAsync()` in `test` or `afterEach`',
+      input: `
+          import { fakeAsync } from '@angular/core/testing';
+
+          describe('My fakeAsync suite', () => {
+            afterEach(fakeAsync(() => {
+              console.log('afterEach');
+            }));
+
+            it('works', fakeAsync(() => {
+              expect(1).toBe(1);
+            }));
+          });
+      `,
+      expected: `
+          describe('My fakeAsync suite', () => {
+            beforeEach(() => {
+              vi.useFakeTimers({ advanceTimeDelta: 1, shouldAdvanceTime: true });
+            });
+            afterEach(() => {
+              vi.useRealTimers();
+            });
+            afterEach(async () => {
+              console.log('afterEach');
+            });
+
+            it('works', async () => {
+              expect(1).toBe(1);
+            });
+          });
+      `,
+    },
+    {
+      description:
+        'should not append `vi.runOnlyPendingTimersAsync()` if `flush` option is set to false',
+      input: `
+          import { fakeAsync } from '@angular/core/testing';
+
+          describe('My fakeAsync suite', () => {
+            beforeEach(fakeAsync(() => {
+              console.log('beforeEach');
+            }, {flush: false}));
+          });
+      `,
+      expected: `
+          describe('My fakeAsync suite', () => {
+            beforeEach(() => {
+              vi.useFakeTimers({ advanceTimeDelta: 1, shouldAdvanceTime: true });
+            });
+            afterEach(() => {
+              vi.useRealTimers();
+            });
+            beforeEach(async () => {
+              console.log('beforeEach');
+            });
+          });
+      `,
+    },
   ];
 
   testCases.forEach(({ description, input, expected }) => {