[Fix] prefer-read-only-props: add TS support

Author: HenryBrown0

CHANGELOG.md

@@ -21,12 +21,14 @@ This change log adheres to standards from [Keep a CHANGELOG](https://keepachange
 * [`no-unused-state`]: avoid crashing on a class field function with destructured state ([#3568][] @ljharb)
 * [`no-unused-prop-types`]: allow using spread with object expression in jsx ([#3570][] @akulsr0)
 * Revert "[`destructuring-assignment`]: Handle destructuring of useContext in SFC" ([#3583][] [#2797][] @102)
+* [`prefer-read-only-props`]: add TS support ([#3593][] @HenryBrown0)
 
 ### Changed
 * [Docs] [`jsx-newline`], [`no-unsafe`], [`static-property-placement`]: Fix code syntax highlighting ([#3563][] @nbsp1221)
 * [readme] resore configuration URL ([#3582][] @gokaygurcan)
 * [Docs] [`jsx-no-bind`]: reword performance rationale ([#3581][] @gpoole)
 
+[#3593]: https://github.com/jsx-eslint/eslint-plugin-react/pull/3593
 [#3583]: https://github.com/jsx-eslint/eslint-plugin-react/pull/3583
 [#3582]: https://github.com/jsx-eslint/eslint-plugin-react/pull/3582
 [#3581]: https://github.com/jsx-eslint/eslint-plugin-react/pull/3581

docs/rules/prefer-read-only-props.md

@@ -10,6 +10,8 @@ Using Flow, one can define types for props. This rule enforces that prop types a
 
 Examples of **incorrect** code for this rule:
 
+In Flow:
+
 ```jsx
 type Props = {
   name: string,
@@ -29,8 +31,32 @@ const Hello = (props: {|name: string|}) => (
 );
 ```
 
+In TypeScript:
+
+```tsx
+type Props = {
+  name: string;
+}
+class Hello extends React.Component<Props> {
+  render () {
+    return <div>Hello {this.props.name}</div>;
+  }
+}
+
+interface Props {
+  name: string;
+}
+class Hello extends React.Component<Props> {
+  render () {
+    return <div>Hello {this.props.name}</div>;
+  }
+}
+```
+
 Examples of **correct** code for this rule:
 
+In Flow:
+
 ```jsx
 type Props = {
   +name: string,
@@ -49,3 +75,25 @@ const Hello = (props: {|+name: string|}) => (
   <div>Hello {props.name}</div>
 );
 ```
+
+In TypeScript:
+
+```tsx
+type Props = {
+  readonly name: string;
+}
+class Hello extends React.Component<Props> {
+  render () {
+    return <div>Hello {this.props.name}</div>;
+  }
+}
+
+interface Props {
+  readonly name: string;
+}
+class Hello extends React.Component<Props> {
+  render () {
+    return <div>Hello {this.props.name}</div>;
+  }
+}
+```

lib/rules/prefer-read-only-props.js

@@ -16,6 +16,10 @@ function isFlowPropertyType(node) {
   return node.type === 'ObjectTypeProperty';
 }
 
+function isTypescriptPropertyType(node) {
+  return node.type === 'TSPropertySignature';
+}
+
 function isCovariant(node) {
   return (node.variance && node.variance.kind === 'plus')
     || (
@@ -27,6 +31,14 @@ function isCovariant(node) {
     );
 }
 
+function isReadonly(node) {
+  return (
+    node.typeAnnotation
+    && node.typeAnnotation.parent
+    && node.typeAnnotation.parent.readonly
+  );
+}
+
 // ------------------------------------------------------------------------------
 // Rule Definition
 // ------------------------------------------------------------------------------
@@ -50,38 +62,55 @@ module.exports = {
     schema: [],
   },
 
-  create: Components.detect((context, components) => ({
-    'Program:exit'() {
-      flatMap(
-        values(components.list()),
-        (component) => component.declaredPropTypes || []
-      ).forEach((declaredPropTypes) => {
-        Object.keys(declaredPropTypes).forEach((propName) => {
-          const prop = declaredPropTypes[propName];
-
-          if (!prop.node || !isFlowPropertyType(prop.node)) {
-            return;
-          }
-
-          if (!isCovariant(prop.node)) {
-            report(context, messages.readOnlyProp, 'readOnlyProp', {
-              node: prop.node,
-              data: {
-                name: propName,
-              },
-              fix: (fixer) => {
-                if (!prop.node.variance) {
-                  // Insert covariance
-                  return fixer.insertTextBefore(prop.node, '+');
-                }
-
-                // Replace contravariance with covariance
-                return fixer.replaceText(prop.node.variance, '+');
-              },
-            });
-          }
-        });
+  create: Components.detect((context, components) => {
+    function reportReadOnlyProp(prop, propName, fixer) {
+      report(context, messages.readOnlyProp, 'readOnlyProp', {
+        node: prop.node,
+        data: {
+          name: propName,
+        },
+        fix: fixer,
       });
-    },
-  })),
+    }
+
+    return {
+      'Program:exit'() {
+        flatMap(
+          values(components.list()),
+          (component) => component.declaredPropTypes || []
+        ).forEach((declaredPropTypes) => {
+          Object.keys(declaredPropTypes).forEach((propName) => {
+            const prop = declaredPropTypes[propName];
+            if (!prop.node) {
+              return;
+            }
+
+            if (isFlowPropertyType(prop.node)) {
+              if (!isCovariant(prop.node)) {
+                reportReadOnlyProp(prop, propName, (fixer) => {
+                  if (!prop.node.variance) {
+                    // Insert covariance
+                    return fixer.insertTextBefore(prop.node, '+');
+                  }
+
+                  // Replace contravariance with covariance
+                  return fixer.replaceText(prop.node.variance, '+');
+                });
+              }
+
+              return;
+            }
+
+            if (isTypescriptPropertyType(prop.node)) {
+              if (!isReadonly(prop.node)) {
+                reportReadOnlyProp(prop, propName, (fixer) => (
+                  fixer.insertTextBefore(prop.node, 'readonly ')
+                ));
+              }
+            }
+          });
+        });
+      },
+    };
+  }),
 };

tests/lib/rules/prefer-read-only-props.js

@@ -167,7 +167,7 @@ ruleTester.run('prefer-read-only-props', rule, {
         import React from "react";
 
         interface Props {
-          name: string;
+          readonly name: string;
         }
         
         const MyComponent: React.FC<Props> = ({ name }) => {
@@ -176,7 +176,62 @@ ruleTester.run('prefer-read-only-props', rule, {
         
         export default MyComponent;
       `,
-      features: ['ts'],
+      features: ['ts', 'no-babel-old'],
+    },
+    {
+      code: `
+        import React from "react";
+        type Props = {
+          readonly firstName: string;
+          readonly lastName: string;
+        }
+        const MyComponent: React.FC<Props> = ({ name }) => {
+          return <div>{name}</div>;
+        };
+        export default MyComponent;
+      `,
+      features: ['ts', 'no-babel-old'],
+    },
+    {
+      code: `
+        import React from "react";
+        type Props = {
+          readonly name: string;
+        }
+        const MyComponent: React.FC<Props> = ({ name }) => {
+          return <div>{name}</div>;
+        };
+        export default MyComponent;
+      `,
+      features: ['ts', 'no-babel-old'],
+    },
+    {
+      code: `
+        import React from "react";
+        type Props = {
+          readonly name: string[];
+        }
+        const MyComponent: React.FC<Props> = ({ name }) => {
+          return <div>{name}</div>;
+        };
+        export default MyComponent;
+      `,
+      features: ['ts', 'no-babel-old'],
+    },
+    {
+      code: `
+        import React from "react";
+        type Props = {
+          readonly person: {
+            name: string;
+          }
+        }
+        const MyComponent: React.FC<Props> = ({ name }) => {
+          return <div>{name}</div>;
+        };
+        export default MyComponent;
+      `,
+      features: ['ts', 'no-babel-old'],
     },
   ]),
 
@@ -383,5 +438,100 @@ ruleTester.run('prefer-read-only-props', rule, {
         },
       ],
     },
+    {
+      code: `
+        type Props = {
+          name: string;
+        }
+
+        class Hello extends React.Component<Props> {
+          render () {
+            return <div>Hello {this.props.name}</div>;
+          }
+        }
+      `,
+      output: `
+        type Props = {
+          readonly name: string;
+        }
+
+        class Hello extends React.Component<Props> {
+          render () {
+            return <div>Hello {this.props.name}</div>;
+          }
+        }
+      `,
+      features: ['ts', 'no-babel-old'],
+      errors: [
+        {
+          messageId: 'readOnlyProp',
+          data: { name: 'name' },
+        },
+      ],
+    },
+    {
+      code: `
+        interface Props {
+          name: string;
+        }
+
+        class Hello extends React.Component<Props> {
+          render () {
+            return <div>Hello {this.props.name}</div>;
+          }
+        }
+      `,
+      output: `
+        interface Props {
+          readonly name: string;
+        }
+
+        class Hello extends React.Component<Props> {
+          render () {
+            return <div>Hello {this.props.name}</div>;
+          }
+        }
+      `,
+      features: ['ts', 'no-babel-old'],
+      errors: [
+        {
+          messageId: 'readOnlyProp',
+          data: { name: 'name' },
+        },
+      ],
+    },
+    {
+      code: `
+        type Props = {
+          readonly firstName: string;
+          lastName: string;
+        }
+
+        class Hello extends React.Component<Props> {
+          render () {
+            return <div>Hello {this.props.name}</div>;
+          }
+        }
+      `,
+      output: `
+        type Props = {
+          readonly firstName: string;
+          readonly lastName: string;
+        }
+
+        class Hello extends React.Component<Props> {
+          render () {
+            return <div>Hello {this.props.name}</div>;
+          }
+        }
+      `,
+      features: ['ts', 'no-babel-old'],
+      errors: [
+        {
+          messageId: 'readOnlyProp',
+          data: { name: 'lastName' },
+        },
+      ],
+    },
   ]),
 });