Resolve Flow & Test issues with ReactTestRenderer

This is a manual cherry-pick of 2 PRs, updated to handle differences in the stable branch:
- c78464f8ea - Resolve flow errors with ReactTestRenderer (#7736)
- 7dfa01f9fa - Revert ReactMultiChild to plain object (#7757)

src/renderers/shared/stack/reconciler/ReactOwner.js

@@ -15,6 +15,7 @@
 var invariant = require('invariant');
 
 import type { ReactInstance } from 'ReactInstanceType';
+import type { Transaction } from 'Transaction';
 
 /**
  * @param {?object} object
@@ -73,7 +74,7 @@ var ReactOwner = {
     component: ReactInstance,
     ref: string,
     owner: ReactInstance,
-    transaction,
+    transaction: Transaction,
   ): void {
     invariant(
       isValidOwner(owner),

src/renderers/testing/ReactTestEmptyComponent.js

@@ -13,6 +13,8 @@
 'use strict';
 
 class ReactTestEmptyComponent {
+  _currentElement: null;
+
   constructor() {
     this._currentElement = null;
   }

src/renderers/testing/ReactTestMount.js

@@ -20,8 +20,10 @@ var getHostComponentFromComposite = require('getHostComponentFromComposite');
 var instantiateReactComponent = require('instantiateReactComponent');
 var invariant = require('invariant');
 
-type TestRendererOptions = {
-  createNodeMock: (element: ReactElement) => Object,
+import type { ReactElement } from 'ReactElementType';
+
+export type TestRendererOptions = {
+  createNodeMock: (element: ReactElement) => any,
 };
 
 var defaultTestOptions = {

src/renderers/testing/ReactTestReconcileTransaction.js

@@ -16,6 +16,8 @@ var PooledClass = require('PooledClass');
 var Transaction = require('Transaction');
 var ReactUpdateQueue = require('ReactUpdateQueue');
 
+import type { TestRendererOptions } from 'ReactTestMount';
+
 /**
  * Provides a `CallbackQueue` queue for collecting `onDOMReady` callbacks during
  * the performing of the transaction.
@@ -57,7 +59,7 @@ var TRANSACTION_WRAPPERS = [ON_DOM_READY_QUEUEING];
  *
  * @class ReactTestReconcileTransaction
  */
-function ReactTestReconcileTransaction(testOptions) {
+function ReactTestReconcileTransaction(testOptions: TestRendererOptions) {
   this.reinitializeTransaction();
   this.testOptions = testOptions;
   this.reactMountReady = CallbackQueue.getPooled(this);

src/renderers/testing/ReactTestRenderer.js

@@ -24,11 +24,13 @@ var ReactTestTextComponent = require('ReactTestTextComponent');
 var ReactTestEmptyComponent = require('ReactTestEmptyComponent');
 
 import type { ReactElement } from 'ReactElementType';
+import type { ReactInstance } from 'ReactInstanceType';
 
 type ReactTestRendererJSON = {
   type: string,
   props: { [propName: string]: string },
-  children: Array<string | ReactTestRendererJSON>,
+  children: null | Array<string | ReactTestRendererJSON>,
+  $$typeof?: any
 }
 
 /**
@@ -47,6 +49,10 @@ function getRenderedHostOrTextFromComponent(component) {
 }
 
 class ReactTestComponent {
+  _currentElement: ReactElement;
+  _renderedChildren: null | Object;
+  _topLevelWrapper: null | ReactInstance;
+
   constructor(element: ReactElement) {
     this._currentElement = element;
     this._renderedChildren = null;
@@ -60,6 +66,7 @@ class ReactTestComponent {
     context: Object,
   ) {
     var element = this._currentElement;
+    // $FlowFixMe https://github.com/facebook/flow/issues/1805
     this.mountChildren(element.props.children, transaction, context);
   }
 
@@ -69,6 +76,7 @@ class ReactTestComponent {
     context: Object,
   ) {
     this._currentElement = nextElement;
+    // $FlowFixMe https://github.com/facebook/flow/issues/1805
     this.updateChildren(nextElement.props.children, transaction, context);
   }
 
@@ -89,7 +97,7 @@ class ReactTestComponent {
         childrenJSON.push(json);
       }
     }
-    var object = {
+    var object: ReactTestRendererJSON = {
       type: this._currentElement.type,
       props: props,
       children: childrenJSON.length ? childrenJSON : null,
@@ -104,7 +112,7 @@ class ReactTestComponent {
   unmountComponent(): void {}
 }
 
-Object.assign(ReactTestComponent.prototype, ReactMultiChild);
+Object.assign(ReactTestComponent.prototype, ReactMultiChild.Mixin);
 
 // =============================================================================
 

src/renderers/testing/ReactTestTextComponent.js

@@ -15,6 +15,8 @@
 import type { ReactText } from 'ReactTypes';
 
 class ReactTestTextComponent {
+  _currentElement: ReactText;
+
   constructor(element: ReactText) {
     this._currentElement = element;
   }