From 16b1f5230a23090d7e2f8ad6214366ed40047c7b Mon Sep 17 00:00:00 2001
From: Jordan Harband <ljharb@gmail.com>
Date: Sat, 4 May 2019 14:12:50 -0700
Subject: [PATCH] [Fix] `shallow`: properly determine "should render" for
 `PureComponent`s

Fixes #2096.
---
 .../test/ReactWrapper-spec.jsx                | 35 +++++++++++++++++++
 .../test/ShallowWrapper-spec.jsx              | 33 +++++++++++++++++
 packages/enzyme/src/ShallowWrapper.js         |  2 +-
 3 files changed, 69 insertions(+), 1 deletion(-)

diff --git a/packages/enzyme-test-suite/test/ReactWrapper-spec.jsx b/packages/enzyme-test-suite/test/ReactWrapper-spec.jsx
index bddcc7988..85b9a8eef 100644
--- a/packages/enzyme-test-suite/test/ReactWrapper-spec.jsx
+++ b/packages/enzyme-test-suite/test/ReactWrapper-spec.jsx
@@ -3402,6 +3402,41 @@ describeWithDOM('mount', () => {
           });
         });
       });
+
+      it('does not infinitely loop when a PureComponent fires a noop setState in cDU', () => {
+        class Example extends PureComponent {
+          constructor(props) {
+            super(props);
+
+            this.renders = 0;
+            this.state = {
+              a: false,
+              b: false,
+            };
+          }
+
+          componentDidMount() {
+            this.setState({ b: false });
+          }
+
+          componentDidUpdate() {
+            this.setState({ b: false }); // eslint-disable-line react/no-did-update-set-state
+          }
+
+          render() {
+            this.renders += 1;
+            const { a, b } = this.state;
+            return <div>{`${a} ${b} ${this.renders}`}</div>;
+          }
+        }
+
+        const wrapper = mount(<Example />);
+        expect(wrapper.debug()).to.equal(`<Example>
+  <div>
+    false false 1
+  </div>
+</Example>`);
+      });
     });
 
     describe('Own PureComponent implementation', () => {
diff --git a/packages/enzyme-test-suite/test/ShallowWrapper-spec.jsx b/packages/enzyme-test-suite/test/ShallowWrapper-spec.jsx
index 7c58d2025..62cbd98c4 100644
--- a/packages/enzyme-test-suite/test/ShallowWrapper-spec.jsx
+++ b/packages/enzyme-test-suite/test/ShallowWrapper-spec.jsx
@@ -3802,6 +3802,39 @@ describe('shallow', () => {
           });
         });
       });
+
+      it('does not infinitely loop when a PureComponent fires a noop setState in cDU', () => {
+        class Example extends PureComponent {
+          constructor(props) {
+            super(props);
+
+            this.renders = 0;
+            this.state = {
+              a: false,
+              b: false,
+            };
+          }
+
+          componentDidMount() {
+            this.setState({ b: false });
+          }
+
+          componentDidUpdate() {
+            this.setState({ b: false }); // eslint-disable-line react/no-did-update-set-state
+          }
+
+          render() {
+            this.renders += 1;
+            const { a, b } = this.state;
+            return <div>{`${a} ${b} ${this.renders}`}</div>;
+          }
+        }
+
+        const wrapper = shallow(<Example />);
+        expect(wrapper.debug()).to.equal(`<div>
+  false false 1
+</div>`);
+      });
     });
 
     describe('Own PureComponent implementation', () => {
diff --git a/packages/enzyme/src/ShallowWrapper.js b/packages/enzyme/src/ShallowWrapper.js
index 99941e553..c068b3f01 100644
--- a/packages/enzyme/src/ShallowWrapper.js
+++ b/packages/enzyme/src/ShallowWrapper.js
@@ -778,7 +778,7 @@ class ShallowWrapper {
             prevProps,
             instance.props,
             prevState,
-            statePayload,
+            { ...prevState, ...statePayload },
           );
         }