Rewrite SyntheticEvent tests using public APIs only (#11525)

* generate synthetics events using public API

* rewritten createEvent to use public APIs
* removed all references SyntheticEvent.release

In order to test under realistic circumstances I had to move
the expectations into a callback in mosts tests to overcome
the effects of event pooling.

* run prettier

* remove empty line

* don't use ReactTestUtils

* run prettier and fix linter issues

* remove duplicate test

* remove invalid calls to expect

The removed `expect` calls verified the correct behaviour based on
missing `preventDefault` and `stopPropagation` methods.
The was correct as we used plain objects to simulate events.
Since we switched to the public API we're using native events which
do have these methods.

* set event.defaultPrevented to undefined

This was missed when the test was first migrated.
When emulating IE8 not only has returnValue to be false.
In addition defaultPrevented must not be defined.

* run all tests and format code

* rename instance variable to node

* remove backtick

* only simulate IE in normalisation test

* include assignment in definition

* add missing `persist` test

* use method instead of field to prevent default

* expect properties to be unchanged on persisted event

* optimise tests that deal with event persitence

* declare and assign `event` on the same line if not reassigned later

packages/react-dom/src/events/__tests__/SyntheticEvent-test.js

@@ -9,79 +9,170 @@
 
 'use strict';
 
-var SyntheticEvent;
 var React;
 var ReactDOM;
 var ReactTestUtils;
 
 describe('SyntheticEvent', () => {
-  var createEvent;
+  var container;
 
   beforeEach(() => {
-    // TODO: can we express this test with only public API?
-    SyntheticEvent = require('events/SyntheticEvent').default;
     React = require('react');
     ReactDOM = require('react-dom');
     ReactTestUtils = require('react-dom/test-utils');
 
-    createEvent = function(nativeEvent) {
-      var target = require('../getEventTarget').default(nativeEvent);
-      return SyntheticEvent.getPooled({}, '', nativeEvent, target);
-    };
+    container = document.createElement('div');
+    document.body.appendChild(container);
+  });
+
+  afterEach(() => {
+    document.body.removeChild(container);
+    container = null;
   });
 
   it('should normalize `target` from the nativeEvent', () => {
-    var target = document.createElement('div');
-    var syntheticEvent = createEvent({srcElement: target});
+    var node;
+    var expectedCount = 0;
 
-    expect(syntheticEvent.target).toBe(target);
-    expect(syntheticEvent.type).toBe(undefined);
+    var eventHandler = syntheticEvent => {
+      expect(syntheticEvent.target).toBe(node);
+
+      expectedCount++;
+    };
+    node = ReactDOM.render(<div onClick={eventHandler} />, container);
+
+    var event = document.createEvent('Event');
+    event.initEvent('click', true, true);
+    // Emulate IE8
+    Object.defineProperty(event, 'target', {
+      get() {},
+    });
+    Object.defineProperty(event, 'srcElement', {
+      get() {
+        return node;
+      },
+    });
+    node.dispatchEvent(event);
+
+    expect(expectedCount).toBe(1);
   });
 
   it('should be able to `preventDefault`', () => {
-    var nativeEvent = {};
-    var syntheticEvent = createEvent(nativeEvent);
+    var node;
+    var expectedCount = 0;
 
-    expect(syntheticEvent.isDefaultPrevented()).toBe(false);
-    syntheticEvent.preventDefault();
-    expect(syntheticEvent.isDefaultPrevented()).toBe(true);
+    var eventHandler = syntheticEvent => {
+      expect(syntheticEvent.isDefaultPrevented()).toBe(false);
+      syntheticEvent.preventDefault();
+      expect(syntheticEvent.isDefaultPrevented()).toBe(true);
+      expect(syntheticEvent.defaultPrevented).toBe(true);
 
-    expect(syntheticEvent.defaultPrevented).toBe(true);
+      expectedCount++;
+    };
+    node = ReactDOM.render(<div onClick={eventHandler} />, container);
 
-    expect(nativeEvent.returnValue).toBe(false);
+    var event = document.createEvent('Event');
+    event.initEvent('click', true, true);
+    node.dispatchEvent(event);
+
+    expect(expectedCount).toBe(1);
   });
 
   it('should be prevented if nativeEvent is prevented', () => {
-    expect(createEvent({defaultPrevented: true}).isDefaultPrevented()).toBe(
-      true,
-    );
-    expect(createEvent({returnValue: false}).isDefaultPrevented()).toBe(true);
+    var node;
+    var expectedCount = 0;
+
+    var eventHandler = syntheticEvent => {
+      expect(syntheticEvent.isDefaultPrevented()).toBe(true);
+
+      expectedCount++;
+    };
+    node = ReactDOM.render(<div onClick={eventHandler} />, container);
+
+    var event;
+    event = document.createEvent('Event');
+    event.initEvent('click', true, true);
+    event.preventDefault();
+    node.dispatchEvent(event);
+
+    event = document.createEvent('Event');
+    event.initEvent('click', true, true);
+    // Emulate IE8
+    Object.defineProperty(event, 'defaultPrevented', {
+      get() {},
+    });
+    Object.defineProperty(event, 'returnValue', {
+      get() {
+        return false;
+      },
+    });
+    node.dispatchEvent(event);
+
+    expect(expectedCount).toBe(2);
   });
 
   it('should be able to `stopPropagation`', () => {
-    var nativeEvent = {};
-    var syntheticEvent = createEvent(nativeEvent);
+    var node;
+    var expectedCount = 0;
 
-    expect(syntheticEvent.isPropagationStopped()).toBe(false);
-    syntheticEvent.stopPropagation();
-    expect(syntheticEvent.isPropagationStopped()).toBe(true);
+    var eventHandler = syntheticEvent => {
+      expect(syntheticEvent.isPropagationStopped()).toBe(false);
+      syntheticEvent.stopPropagation();
+      expect(syntheticEvent.isPropagationStopped()).toBe(true);
 
-    expect(nativeEvent.cancelBubble).toBe(true);
+      expectedCount++;
+    };
+    node = ReactDOM.render(<div onClick={eventHandler} />, container);
+
+    var event = document.createEvent('Event');
+    event.initEvent('click', true, true);
+    node.dispatchEvent(event);
+
+    expect(expectedCount).toBe(1);
   });
 
   it('should be able to `persist`', () => {
-    var syntheticEvent = createEvent({});
+    var node;
+    var expectedCount = 0;
+    var syntheticEvent;
 
-    expect(syntheticEvent.isPersistent()).toBe(false);
-    syntheticEvent.persist();
-    expect(syntheticEvent.isPersistent()).toBe(true);
+    var eventHandler = e => {
+      expect(e.isPersistent()).toBe(false);
+      e.persist();
+      syntheticEvent = e;
+      expect(e.isPersistent()).toBe(true);
+
+      expectedCount++;
+    };
+    node = ReactDOM.render(<div onClick={eventHandler} />, container);
+
+    var event = document.createEvent('Event');
+    event.initEvent('click', true, true);
+    node.dispatchEvent(event);
+
+    expect(syntheticEvent.type).toBe('click');
+    expect(syntheticEvent.bubbles).toBe(true);
+    expect(syntheticEvent.cancelable).toBe(true);
+    expect(expectedCount).toBe(1);
   });
 
-  it('should be nullified if the synthetic event has called destructor and log warnings', () => {
+  it('should be nullified and log warnings if the synthetic event has not been persisted', () => {
     spyOn(console, 'error');
-    var target = document.createElement('div');
-    var syntheticEvent = createEvent({srcElement: target});
-    syntheticEvent.destructor();
+    var node;
+    var expectedCount = 0;
+    var syntheticEvent;
+
+    var eventHandler = e => {
+      syntheticEvent = e;
+
+      expectedCount++;
+    };
+    node = ReactDOM.render(<div onClick={eventHandler} />, container);
+
+    var event = document.createEvent('Event');
+    event.initEvent('click', true, true);
+    node.dispatchEvent(event);
+
     expect(syntheticEvent.type).toBe(null);
     expect(syntheticEvent.nativeEvent).toBe(null);
     expect(syntheticEvent.target).toBe(null);
@@ -95,14 +186,27 @@ describe('SyntheticEvent', () => {
         'keep the original synthetic event around, use event.persist(). ' +
         'See https://fb.me/react-event-pooling for more information.',
     );
+    expect(expectedCount).toBe(1);
   });
 
-  it('should warn when setting properties of a destructored synthetic event', () => {
+  it('should warn when setting properties of a synthetic event that has not been persisted', () => {
     spyOn(console, 'error');
-    var target = document.createElement('div');
-    var syntheticEvent = createEvent({srcElement: target});
-    syntheticEvent.destructor();
-    expect((syntheticEvent.type = 'MouseEvent')).toBe('MouseEvent');
+    var node;
+    var expectedCount = 0;
+    var syntheticEvent;
+
+    var eventHandler = e => {
+      syntheticEvent = e;
+
+      expectedCount++;
+    };
+    node = ReactDOM.render(<div onClick={eventHandler} />, container);
+
+    var event = document.createEvent('Event');
+    event.initEvent('click', true, true);
+    node.dispatchEvent(event);
+
+    syntheticEvent.type = 'MouseEvent';
     expectDev(console.error.calls.count()).toBe(1);
     expectDev(console.error.calls.argsFor(0)[0]).toBe(
       'Warning: This synthetic event is reused for performance reasons. If ' +
@@ -111,12 +215,25 @@ describe('SyntheticEvent', () => {
         'keep the original synthetic event around, use event.persist(). ' +
         'See https://fb.me/react-event-pooling for more information.',
     );
+    expect(expectedCount).toBe(1);
   });
 
-  it('should warn if the synthetic event has been released when calling `preventDefault`', () => {
+  it('should warn when calling `preventDefault` if the synthetic event has not been persisted', () => {
     spyOn(console, 'error');
-    var syntheticEvent = createEvent({});
-    SyntheticEvent.release(syntheticEvent);
+    var node;
+    var expectedCount = 0;
+    var syntheticEvent;
+
+    var eventHandler = e => {
+      syntheticEvent = e;
+      expectedCount++;
+    };
+    node = ReactDOM.render(<div onClick={eventHandler} />, container);
+
+    var event = document.createEvent('Event');
+    event.initEvent('click', true, true);
+    node.dispatchEvent(event);
+
     syntheticEvent.preventDefault();
     expectDev(console.error.calls.count()).toBe(1);
     expectDev(console.error.calls.argsFor(0)[0]).toBe(
@@ -126,12 +243,26 @@ describe('SyntheticEvent', () => {
         'keep the original synthetic event around, use event.persist(). ' +
         'See https://fb.me/react-event-pooling for more information.',
     );
+    expect(expectedCount).toBe(1);
   });
 
-  it('should warn if the synthetic event has been released when calling `stopPropagation`', () => {
+  it('should warn when calling `stopPropagation` if the synthetic event has not been persisted', () => {
     spyOn(console, 'error');
-    var syntheticEvent = createEvent({});
-    SyntheticEvent.release(syntheticEvent);
+    var node;
+    var expectedCount = 0;
+    var syntheticEvent;
+
+    var eventHandler = e => {
+      syntheticEvent = e;
+      expectedCount++;
+    };
+    node = ReactDOM.render(<div onClick={eventHandler} />, container);
+
+    var event = document.createEvent('Event');
+    event.initEvent('click', true, true);
+
+    node.dispatchEvent(event);
+
     syntheticEvent.stopPropagation();
     expectDev(console.error.calls.count()).toBe(1);
     expectDev(console.error.calls.argsFor(0)[0]).toBe(
@@ -141,6 +272,7 @@ describe('SyntheticEvent', () => {
         'keep the original synthetic event around, use event.persist(). ' +
         'See https://fb.me/react-event-pooling for more information.',
     );
+    expect(expectedCount).toBe(1);
   });
 
   // TODO: reenable this test. We are currently silencing these warnings when
@@ -153,8 +285,8 @@ describe('SyntheticEvent', () => {
     function assignEvent(e) {
       event = e;
     }
-    var instance = ReactDOM.render(<div onClick={assignEvent} />, element);
-    ReactTestUtils.Simulate.click(ReactDOM.findDOMNode(instance));
+    var node = ReactDOM.render(<div onClick={assignEvent} />, element);
+    ReactTestUtils.Simulate.click(ReactDOM.findDOMNode(node));
     expectDev(console.error.calls.count()).toBe(0);
 
     // access a property to cause the warning
@@ -172,9 +304,22 @@ describe('SyntheticEvent', () => {
 
   it('should warn if Proxy is supported and the synthetic event is added a property', () => {
     spyOn(console, 'error');
-    var syntheticEvent = createEvent({});
-    syntheticEvent.foo = 'bar';
-    SyntheticEvent.release(syntheticEvent);
+    var node;
+    var expectedCount = 0;
+    var syntheticEvent;
+
+    var eventHandler = e => {
+      e.foo = 'bar';
+      syntheticEvent = e;
+      expectedCount++;
+    };
+    node = ReactDOM.render(<div onClick={eventHandler} />, container);
+
+    var event = document.createEvent('Event');
+    event.initEvent('click', true, true);
+
+    node.dispatchEvent(event);
+
     expect(syntheticEvent.foo).toBe('bar');
     if (typeof Proxy === 'function') {
       expectDev(console.error.calls.count()).toBe(1);
@@ -187,5 +332,6 @@ describe('SyntheticEvent', () => {
     } else {
       expectDev(console.error.calls.count()).toBe(0);
     }
+    expect(expectedCount).toBe(1);
   });
 });