Fix #2358 - Recognize props wrapped in flow $ReadOnly<> utility type

Author: lukeapage

lib/util/propTypes.js

@@ -545,6 +545,16 @@ module.exports = function propTypesInstructions(context, components, utils) {
       case 'IntersectionTypeAnnotation':
         ignorePropsValidation = declarePropTypesForIntersectionTypeAnnotation(propTypes, declaredPropTypes);
         break;
+      case 'GenericTypeAnnotation':
+        if (propTypes.id.name === '$ReadOnly') {
+          ignorePropsValidation = declarePropTypesForObjectTypeAnnotation(
+            propTypes.typeParameters.params[0],
+            declaredPropTypes
+          );
+        } else {
+          ignorePropsValidation = true;
+        }
+        break;
       case null:
         break;
       default:

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

@@ -2710,6 +2710,17 @@ ruleTester.run('no-unused-prop-types', rule, {
         };
       `,
       parser: parsers.BABEL_ESLINT
+    }, {
+      code: [
+        'type Props = $ReadOnly<{foo: number}>;',
+        'class Hello extends React.Component {',
+        '  props: Props;',
+        '  render () {',
+        '    return <div>{this.props.foo}</div>;',
+        '  }',
+        '}'
+      ].join('\n'),
+      parser: parsers.BABEL_ESLINT
     }, {
       // issue #933
       code: `
@@ -3656,6 +3667,20 @@ ruleTester.run('no-unused-prop-types', rule, {
       errors: [
         {message: '\'unused\' PropType is defined but prop is never used'}
       ]
+    }, {
+      code: [
+        'type Props = $ReadOnly<{unused: Object;}>;',
+        'class Hello extends React.Component {',
+        '  props: Props;',
+        '  render () {',
+        '    return <div>Hello {this.props.firstname}</div>;',
+        '  }',
+        '}'
+      ].join('\n'),
+      parser: parsers.BABEL_ESLINT,
+      errors: [
+        {message: '\'unused\' PropType is defined but prop is never used'}
+      ]
     }, {
       code: `
       type PropsA = { a: string }