feat: add support for generator functions in specs (jestjs#5166)

* feat: add support for generator functions in specs

Fixes jestjs#2666

* docs: update changelog with PR link

CHANGELOG.md

@@ -1,14 +1,15 @@
 ## master
 
-None for now
-
 ### Fixes
 
 * `[babel-jest]` moduleFileExtensions not passed to babel transformer.
   ([#4637](https://github.com/facebook/jest/issues/4637))
 
 ### Features
 
+* `[jest-jasmine2]` Support generator functions as specs.
+  ([#5166](https://github.com/facebook/jest/pull/5166))
+
 ### Chore & Maintenance
 
 ## jest 22.0.1

docs/GlobalAPI.md

@@ -17,7 +17,8 @@ environment. You don't have to require or import anything to use them.
 ### `afterAll(fn, timeout)`
 
 Runs a function after all the tests in this file have completed. If the function
-returns a promise, Jest waits for that promise to resolve before continuing.
+returns a promise or is a generator, Jest waits for that promise to resolve
+before continuing.
 
 Optionally, you can provide a `timeout` (in milliseconds) for specifying how
 long to wait before aborting. _Note: The default timeout is 5 seconds._
@@ -63,8 +64,8 @@ If you want to run some cleanup after every test instead of after all tests, use
 ### `afterEach(fn, timeout)`
 
 Runs a function after each one of the tests in this file completes. If the
-function returns a promise, Jest waits for that promise to resolve before
-continuing.
+function returns a promise or is a generator, Jest waits for that promise to
+resolve before continuing.
 
 Optionally, you can provide a `timeout` (in milliseconds) for specifying how
 long to wait before aborting. _Note: The default timeout is 5 seconds._
@@ -110,7 +111,8 @@ If you want to run some cleanup just once, after all of the tests run, use
 ### `beforeAll(fn, timeout)`
 
 Runs a function before any of the tests in this file run. If the function
-returns a promise, Jest waits for that promise to resolve before running tests.
+returns a promise or is a generator, Jest waits for that promise to resolve
+before running tests.
 
 Optionally, you can provide a `timeout` (in milliseconds) for specifying how
 long to wait before aborting. _Note: The default timeout is 5 seconds._
@@ -154,8 +156,8 @@ use `beforeEach` instead.
 ### `beforeEach(fn, timeout)`
 
 Runs a function before each of the tests in this file runs. If the function
-returns a promise, Jest waits for that promise to resolve before running the
-test.
+returns a promise or is a generator, Jest waits for that promise to resolve
+before running the test.
 
 Optionally, you can provide a `timeout` (in milliseconds) for specifying how
 long to wait before aborting. _Note: The default timeout is 5 seconds._

integration_tests/__tests__/jasmine_async.test.js

@@ -141,4 +141,10 @@ describe('async jasmine', () => {
       expect.stringContaining('Expected value to be truthy, instead received'),
     );
   });
+
+  it('generator test', () => {
+    const result = runJest('jasmine_async', ['generator.test.js']);
+
+    expect(result.status).toBe(0);
+  });
 });

integration_tests/jasmine_async/__tests__/generator.test.js

@@ -0,0 +1,25 @@
+/**
+ * Copyright (c) 2014-present, Facebook, Inc. All rights reserved.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+'use strict';
+
+function* someFunc() {
+  return 3;
+}
+
+describe('generators', () => {
+  beforeEach(function*() {
+    // This shouldn't throw
+    yield someFunc();
+  });
+
+  it('in spec', function*() {
+    const data = yield someFunc();
+
+    expect(data).toBe(3);
+  });
+});

packages/jest-jasmine2/package.json

@@ -10,8 +10,10 @@
   "dependencies": {
     "callsites": "^2.0.0",
     "chalk": "^2.0.1",
+    "co": "^4.6.0",
     "expect": "^22.0.3",
     "graceful-fs": "^4.1.11",
+    "is-generator-fn": "^1.0.0",
     "jest-diff": "^22.0.3",
     "jest-matcher-utils": "^22.0.3",
     "jest-message-util": "^22.0.3",

packages/jest-jasmine2/src/jasmine_async.js

@@ -14,6 +14,9 @@
 
 import type {Global} from 'types/Global';
 
+import isGeneratorFn from 'is-generator-fn';
+import co from 'co';
+
 function isPromise(obj) {
   return obj && typeof obj.then === 'function';
 }
@@ -34,7 +37,8 @@ function promisifyLifeCycleFunction(originalFn, env) {
     // We make *all* functions async and run `done` right away if they
     // didn't return a promise.
     const asyncFn = function(done) {
-      const returnValue = fn.call({});
+      const wrappedFn = isGeneratorFn(fn) ? co.wrap(fn) : fn;
+      const returnValue = wrappedFn.call({});
 
       if (isPromise(returnValue)) {
         returnValue.then(done.bind(null, null), done.fail);
@@ -64,7 +68,8 @@ function promisifyIt(originalFn, env) {
     }
 
     const asyncFn = function(done) {
-      const returnValue = fn.call({});
+      const wrappedFn = isGeneratorFn(fn) ? co.wrap(fn) : fn;
+      const returnValue = wrappedFn.call({});
 
       if (isPromise(returnValue)) {
         returnValue.then(done.bind(null, null), done.fail);

yarn.lock

@@ -3988,6 +3988,10 @@ is-fullwidth-code-point@^2.0.0:
   version "2.0.0"
   resolved "https://registry.yarnpkg.com/is-fullwidth-code-point/-/is-fullwidth-code-point-2.0.0.tgz#a3b30a5c4f199183167aaab93beefae3ddfb654f"
 
+is-generator-fn@^1.0.0:
+  version "1.0.0"
+  resolved "https://registry.yarnpkg.com/is-generator-fn/-/is-generator-fn-1.0.0.tgz#969d49e1bb3329f6bb7f09089be26578b2ddd46a"
+
 is-glob@^2.0.0, is-glob@^2.0.1:
   version "2.0.1"
   resolved "https://registry.yarnpkg.com/is-glob/-/is-glob-2.0.1.tgz#d096f926a3ded5600f3fdfd91198cb0888c2d863"