From fdee5c7a6e7665a6c54073f86747ffb04cfed660 Mon Sep 17 00:00:00 2001
From: fatfisz <fatfisz@gmail.com>
Date: Tue, 12 Jun 2018 21:25:32 +0200
Subject: [PATCH 1/2] Call gDSFP with the right state in react-test-render

---
 .../src/ReactShallowRenderer.js               |  4 +--
 .../__tests__/ReactShallowRenderer-test.js    | 33 +++++++++++++++++++
 2 files changed, 35 insertions(+), 2 deletions(-)

diff --git a/packages/react-test-renderer/src/ReactShallowRenderer.js b/packages/react-test-renderer/src/ReactShallowRenderer.js
index 3134f991eeaf2..0c1f7178831f9 100644
--- a/packages/react-test-renderer/src/ReactShallowRenderer.js
+++ b/packages/react-test-renderer/src/ReactShallowRenderer.js
@@ -238,14 +238,14 @@ class ReactShallowRenderer {
     const {type} = this._element;
 
     if (typeof type.getDerivedStateFromProps === 'function') {
+      const oldState = this._newState || this._instance.state;
       const partialState = type.getDerivedStateFromProps.call(
         null,
         props,
-        this._instance.state,
+        oldState,
       );
 
       if (partialState != null) {
-        const oldState = this._newState || this._instance.state;
         const newState = Object.assign({}, oldState, partialState);
         this._instance.state = this._newState = newState;
       }
diff --git a/packages/react-test-renderer/src/__tests__/ReactShallowRenderer-test.js b/packages/react-test-renderer/src/__tests__/ReactShallowRenderer-test.js
index eb8942a520959..fc86d33712464 100644
--- a/packages/react-test-renderer/src/__tests__/ReactShallowRenderer-test.js
+++ b/packages/react-test-renderer/src/__tests__/ReactShallowRenderer-test.js
@@ -915,6 +915,39 @@ describe('ReactShallowRenderer', () => {
     expect(result.props.children).toEqual(3);
   });
 
+  it('should call getDerivedStateFromProps with the state set by setState', () => {
+    class SimpleComponent extends React.Component {
+      state = {count: 1};
+
+      static getDerivedStateFromProps(nextProps, prevState) {
+        if (nextProps.updateState) {
+          return {count: nextProps.incrementBy + prevState.count};
+        }
+
+        return null;
+      }
+
+      render() {
+        return <div>{this.state.count}</div>;
+      }
+    }
+
+    const shallowRenderer = createRenderer();
+    shallowRenderer.render(
+      <SimpleComponent updateState={false} incrementBy={2} />,
+    );
+    let instance = shallowRenderer.getMountedInstance();
+    instance.setState({count: 2});
+    expect(instance.state.count).toEqual(2);
+
+    shallowRenderer.render(
+      <SimpleComponent updateState={true} incrementBy={2} />,
+    );
+    instance = shallowRenderer.getMountedInstance();
+    instance.setState({count: 2});
+    expect(instance.state.count).toEqual(4);
+  });
+
   it('can setState with an updater function', () => {
     let instance;
 

From 98821dba04c0890bae8a721da22d89688a7b2027 Mon Sep 17 00:00:00 2001
From: fatfisz <fatfisz@gmail.com>
Date: Wed, 13 Jun 2018 00:20:19 +0200
Subject: [PATCH 2/2] Change the test

---
 .../__tests__/ReactShallowRenderer-test.js    | 34 ++++++++-----------
 1 file changed, 14 insertions(+), 20 deletions(-)

diff --git a/packages/react-test-renderer/src/__tests__/ReactShallowRenderer-test.js b/packages/react-test-renderer/src/__tests__/ReactShallowRenderer-test.js
index fc86d33712464..b47495bca9818 100644
--- a/packages/react-test-renderer/src/__tests__/ReactShallowRenderer-test.js
+++ b/packages/react-test-renderer/src/__tests__/ReactShallowRenderer-test.js
@@ -915,37 +915,31 @@ describe('ReactShallowRenderer', () => {
     expect(result.props.children).toEqual(3);
   });
 
-  it('should call getDerivedStateFromProps with the state set by setState', () => {
+  it('should not override state with stale values if prevState is spread within getDerivedStateFromProps', () => {
     class SimpleComponent extends React.Component {
-      state = {count: 1};
+      state = {value: 0};
 
       static getDerivedStateFromProps(nextProps, prevState) {
-        if (nextProps.updateState) {
-          return {count: nextProps.incrementBy + prevState.count};
-        }
-
-        return null;
+        return {...prevState};
       }
 
+      updateState = () => {
+        this.setState(state => ({value: state.value + 1}));
+      };
+
       render() {
-        return <div>{this.state.count}</div>;
+        return <div>{`value:${this.state.value}`}</div>;
       }
     }
 
     const shallowRenderer = createRenderer();
-    shallowRenderer.render(
-      <SimpleComponent updateState={false} incrementBy={2} />,
-    );
-    let instance = shallowRenderer.getMountedInstance();
-    instance.setState({count: 2});
-    expect(instance.state.count).toEqual(2);
+    let result = shallowRenderer.render(<SimpleComponent />);
+    expect(result).toEqual(<div>value:0</div>);
 
-    shallowRenderer.render(
-      <SimpleComponent updateState={true} incrementBy={2} />,
-    );
-    instance = shallowRenderer.getMountedInstance();
-    instance.setState({count: 2});
-    expect(instance.state.count).toEqual(4);
+    let instance = shallowRenderer.getMountedInstance();
+    instance.updateState();
+    result = shallowRenderer.getRenderOutput();
+    expect(result).toEqual(<div>value:1</div>);
   });
 
   it('can setState with an updater function', () => {