[Shallow] Implement callEffects option (facebook#15275)

packages/react-test-renderer/src/ReactShallowRenderer.js

@@ -91,6 +91,17 @@ function areHookInputsEqual(
   return true;
 }
 
+function doEffectInputsDiffer(
+  before: Array<mixed>,
+  after: Array<mixed> | void | null,
+) {
+  if (after == null || before.length !== after.length) {
+    return true;
+  }
+
+  return before.some((value, i) => after[i] !== value);
+}
+
 class Updater {
   constructor(renderer) {
     this._renderer = renderer;
@@ -172,12 +183,21 @@ function basicStateReducer<S>(state: S, action: BasicStateAction<S>): S {
   return typeof action === 'function' ? action(state) : action;
 }
 
+type ShallowRenderOptions = {
+  callEffects: boolean,
+};
+
+const isEffectHook = Symbol();
+
 class ReactShallowRenderer {
-  static createRenderer = function() {
-    return new ReactShallowRenderer();
+  static createRenderer = function(
+    options: ShallowRenderOptions = {callEffects: false},
+  ) {
+    return new ReactShallowRenderer(options);
   };
 
-  constructor() {
+  constructor(options: ShallowRenderOptions) {
+    this._options = options;
     this._reset();
   }
 
@@ -199,6 +219,7 @@ class ReactShallowRenderer {
     this._numberOfReRenders = 0;
   }
 
+  _options: ShallowRenderOptions;
   _context: null | Object;
   _newState: null | Object;
   _instance: any;
@@ -308,6 +329,54 @@ class ReactShallowRenderer {
       );
     };
 
+    const useGenericEffect = (
+      create: () => (() => void) | void,
+      inputs: Array<mixed> | void | null,
+      isLayoutEffect: boolean,
+    ) => {
+      this._validateCurrentlyRenderingComponent();
+      this._createWorkInProgressHook();
+
+      if (this._workInProgressHook !== null) {
+        if (this._workInProgressHook.memoizedState == null) {
+          this._workInProgressHook.memoizedState = {
+            isEffectHook,
+            isLayoutEffect,
+            create,
+            inputs,
+            cleanup: null,
+            run: true,
+          };
+        } else {
+          const {memoizedState} = this._workInProgressHook;
+          this._workInProgressHook.memoizedState = {
+            isEffectHook,
+            isLayoutEffect,
+            create,
+            inputs,
+            cleanup: memoizedState.cleanup,
+            run:
+              inputs == null ||
+              doEffectInputsDiffer(inputs, memoizedState.inputs),
+          };
+        }
+      }
+    };
+
+    const useEffect = (
+      create: () => (() => void) | void,
+      inputs: Array<mixed> | void | null,
+    ) => {
+      useGenericEffect(create, inputs, false);
+    };
+
+    const useLayoutEffect = (
+      create: () => (() => void) | void,
+      inputs: Array<mixed> | void | null,
+    ) => {
+      useGenericEffect(create, inputs, true);
+    };
+
     const useMemo = <T>(
       nextCreate: () => T,
       deps: Array<mixed> | void | null,
@@ -374,9 +443,9 @@ class ReactShallowRenderer {
         return readContext(context);
       },
       useDebugValue: noOp,
-      useEffect: noOp,
+      useEffect: this._options.callEffects ? useEffect : noOp,
       useImperativeHandle: noOp,
-      useLayoutEffect: noOp,
+      useLayoutEffect: this._options.callEffects ? useLayoutEffect : noOp,
       useMemo,
       useReducer,
       useRef,
@@ -619,6 +688,7 @@ class ReactShallowRenderer {
             ReactCurrentDispatcher.current = prevDispatcher;
           }
           this._finishHooks(element, context);
+          this._callEffectsIfDesired();
         }
       }
     }
@@ -679,6 +749,36 @@ class ReactShallowRenderer {
     // because DOM refs are not available.
   }
 
+  _callEffectsIfDesired() {
+    if (!this._options.callEffects) {
+      return;
+    }
+
+    this._callEffects(true);
+    this._callEffects(false);
+  }
+
+  _callEffects(callLayoutEffects: boolean) {
+    for (
+      let hook = this._firstWorkInProgressHook;
+      hook !== null;
+      hook = hook.next
+    ) {
+      const {memoizedState} = hook;
+      if (
+        memoizedState != null &&
+        memoizedState.isEffectHook === isEffectHook &&
+        memoizedState.isLayoutEffect === callLayoutEffects &&
+        memoizedState.run
+      ) {
+        if (memoizedState.cleanup) {
+          memoizedState.cleanup();
+        }
+        memoizedState.cleanup = memoizedState.create();
+      }
+    }
+  }
+
   _updateClassComponent(
     elementType: Function,
     element: ReactElement,

packages/react-test-renderer/src/__tests__/ReactShallowRendererHooks-test.js

@@ -231,7 +231,7 @@ describe('ReactShallowRenderer with hooks', () => {
     );
   });
 
-  it('should not trigger effects', () => {
+  it('should not trigger effects by default', () => {
     let effectsCalled = [];
 
     function SomeComponent({defaultName}) {
@@ -252,6 +252,36 @@ describe('ReactShallowRenderer with hooks', () => {
     expect(effectsCalled).toEqual([]);
   });
 
+  describe('when callEffects option is used', () => {
+    it('should trigger effects after render', () => {
+      let happenings = [];
+
+      function SomeComponent({defaultName}) {
+        // Will be triggered *after* the layout effect.
+        React.useEffect(() => {
+          happenings.push('call effect');
+        });
+
+        React.useLayoutEffect(() => {
+          happenings.push('call layout effect');
+        });
+
+        happenings.push('render');
+
+        return <div>Hello world</div>;
+      }
+
+      const shallowRenderer = createRenderer({callEffects: true});
+      shallowRenderer.render(<SomeComponent />);
+
+      expect(happenings).toEqual([
+        'render',
+        'call layout effect',
+        'call effect',
+      ]);
+    });
+  });
+
   it('should work with useRef', () => {
     function SomeComponent() {
       const randomNumberRef = React.useRef({number: Math.random()});