Add getSnapshotBeforeUpdate support to no-unused-prop-types (fixes #1751)

Author: yannickcr

lib/rules/no-unused-prop-types.js

@@ -23,7 +23,7 @@ const DIRECT_PROPS_REGEX = /^props\s*(\.|\[)/;
 const DIRECT_NEXT_PROPS_REGEX = /^nextProps\s*(\.|\[)/;
 const DIRECT_PREV_PROPS_REGEX = /^prevProps\s*(\.|\[)/;
 const LIFE_CYCLE_METHODS = ['componentWillReceiveProps', 'shouldComponentUpdate', 'componentWillUpdate', 'componentDidUpdate'];
-const ASYNC_SAFE_LIFE_CYCLE_METHODS = ['getDerivedStateFromProps', 'UNSAFE_componentWillReceiveProps', 'UNSAFE_componentWillUpdate'];
+const ASYNC_SAFE_LIFE_CYCLE_METHODS = ['getDerivedStateFromProps', 'getSnapshotBeforeUpdate', 'UNSAFE_componentWillReceiveProps', 'UNSAFE_componentWillUpdate'];
 
 // ------------------------------------------------------------------------------
 // Rule Definition

tests/lib/rules/no-unused-prop-types.js

@@ -2880,6 +2880,26 @@ ruleTester.run('no-unused-prop-types', rule, {
       `].join('\n'),
       settings: {react: {version: '16.3.0'}},
       parser: 'babel-eslint'
+    }, {
+      // Simple test of new static getSnapshotBeforeUpdate lifecycle
+      code: [`
+        class MyComponent extends React.Component {
+          static propTypes = {
+            defaultValue: PropTypes.string
+          };
+          getSnapshotBeforeUpdate(prevProps, prevState) {
+            if (prevProps.defaultValue === null) {
+              return 'snapshot';
+            }
+            return null;
+          }
+          render() {
+            return <div />
+          }
+        }
+      `].join('\n'),
+      settings: {react: {version: '16.3.0'}},
+      parser: 'babel-eslint'
     }
   ],
 
@@ -4510,6 +4530,28 @@ ruleTester.run('no-unused-prop-types', rule, {
       errors: [{
         message: '\'defaultValue\' PropType is defined but prop is never used'
       }]
+    }, {
+      code: [`
+        class MyComponent extends React.Component {
+          static propTypes = {
+            defaultValue: PropTypes.string
+          };
+          getSnapshotBeforeUpdate(prevProps, prevState) {
+            if (prevProps.defaultValue === null) {
+              return 'snapshot';
+            }
+            return null;
+          }
+          render() {
+            return <div />
+          }
+        }
+      `].join('\n'),
+      settings: {react: {version: '16.2.0'}},
+      parser: 'babel-eslint',
+      errors: [{
+        message: '\'defaultValue\' PropType is defined but prop is never used'
+      }]
     }
 
     /* , {