feat(plugins/react-x): add jsx-uses-vars, closes #834

package.json

@@ -49,9 +49,9 @@
   "devDependencies": {
     "@changesets/cli": "^2.27.9",
     "@effect/language-service": "^0.2.0",
-    "@effect/platform": "^0.69.9",
-    "@effect/platform-bun": "^0.49.10",
-    "@effect/platform-node": "^0.64.10",
+    "@effect/platform": "^0.69.10",
+    "@effect/platform-bun": "^0.49.11",
+    "@effect/platform-node": "^0.64.11",
     "@effect/schema": "^0.75.5",
     "@eslint/config-inspector": "^0.5.5",
     "@eslint/js": "^9.13.0",
@@ -71,7 +71,7 @@
     "concurrently": "^9.0.1",
     "cspell": "^8.15.4",
     "dprint": "^0.47.5",
-    "effect": "^3.10.4",
+    "effect": "^3.10.5",
     "esbuild": "^0.24.0",
     "eslint": "^9.13.0",
     "eslint-config-flat-gitignore": "^0.3.0",
@@ -87,7 +87,7 @@
     "eslint-plugin-unicorn": "^56.0.0",
     "eslint-plugin-vitest": "^0.5.4",
     "importx": "^0.5.0",
-    "lefthook": "^1.8.1",
+    "lefthook": "^1.8.2",
     "markdownlint": "^0.36.1",
     "publint": "^0.2.12",
     "react": "^18.3.1",

packages/plugins/eslint-plugin-react-x/README.md

@@ -30,6 +30,7 @@ export default [
     rules: {
       // react-x recommended rules
       "react-x/ensure-forward-ref-using-ref": "warn",
+      "react-x/jsx-uses-vars": "warn",
       "react-x/no-access-state-in-setstate": "error",
       "react-x/no-array-index-key": "warn",
       "react-x/no-children-count": "warn",
@@ -74,6 +75,7 @@ export default [
 | `avoid-shorthand-boolean`                | Prevents using shorthand syntax for boolean attributes.                                              | 🎨  |     |     |
 | `avoid-shorthand-fragment`               | Prevents using shorthand syntax for fragments.                                                       | 🎨  |     |     |
 | `ensure-forward-ref-using-ref`           | Requires that components wrapped with `forwardRef` must have a `ref` parameter.                      |  ✔️  |     |     |
+| `jsx-uses-vars                           | Prevents variables used in JSX to be marked as unused.                                               |  ✔️  |     |     |
 | `no-access-state-in-setstate`            | Prevents accessing `this.state` inside `setState` calls.                                             |  ✔️  |     |     |
 | `no-array-index-key`                     | Prevents using array `index` as `key`.                                                               | 🧐  |     |     |
 | `no-children-count`                      | Prevents using `Children.count`.                                                                     | ⛔  |     |     |

packages/plugins/eslint-plugin-react-x/src/index.ts

@@ -5,6 +5,7 @@ import { name, version } from "../package.json";
 import avoidShorthandBoolean from "./rules/avoid-shorthand-boolean";
 import avoidShorthandFragment from "./rules/avoid-shorthand-fragment";
 import forwardRefUsingRef from "./rules/ensure-forward-ref-using-ref";
+import jsxUsesVars from "./rules/jsx-uses-vars";
 import noAccessStateInSetstate from "./rules/no-access-state-in-setstate";
 import noArrayIndexKey from "./rules/no-array-index-key";
 import noChildrenCount from "./rules/no-children-count";
@@ -70,6 +71,7 @@ export default {
     "avoid-shorthand-boolean": avoidShorthandBoolean,
     "avoid-shorthand-fragment": avoidShorthandFragment,
     "ensure-forward-ref-using-ref": forwardRefUsingRef,
+    "jsx-uses-vars": jsxUsesVars,
     "no-access-state-in-setstate": noAccessStateInSetstate,
     "no-array-index-key": noArrayIndexKey,
     "no-children-count": noChildrenCount,

packages/plugins/eslint-plugin-react-x/src/rules/jsx-uses-vars.spec.ts

@@ -0,0 +1,95 @@
+import { allValid, ruleTester } from "../../../../../test";
+import rule, { RULE_NAME } from "./jsx-uses-vars";
+
+ruleTester.run(RULE_NAME, rule, {
+  invalid: [],
+  valid: [
+    ...allValid,
+    {
+      code: /* tsx */ `
+        function foo() {
+          var App;
+          var bar = React.render(<App/>);
+          return bar;
+        };
+        foo()
+      `,
+    },
+    {
+      code: /* tsx */ `
+        var App;
+        React.render(<App/>);
+      `,
+    },
+    {
+      code: /* tsx */ `
+        var a = 1;
+        React.render(<img src={a} />);
+      `,
+    },
+    {
+      code: /* tsx */ `
+        var App;
+        function f() {
+          return <App />;
+        }
+        f();
+      `,
+    },
+    {
+      code: /* tsx */ `
+        var App;
+        <App.Hello />
+      `,
+    },
+    {
+      code: /* tsx */ `
+        class HelloMessage {};
+        <HelloMessage />
+      `,
+    },
+    {
+      code: /* tsx */ `
+        class HelloMessage {
+          render() {
+            var HelloMessage = <div>Hello</div>;
+            return HelloMessage;
+          }
+        };
+        <HelloMessage />
+      `,
+    },
+    {
+      code: /* tsx */ `
+        function foo() {
+          var App = { Foo: { Bar: {} } };
+          var bar = React.render(<App.Foo.Bar/>);
+          return bar;
+        };
+        foo()
+      `,
+    },
+    {
+      code: /* tsx */ `
+        function foo() {
+          var App = { Foo: { Bar: { Baz: {} } } };
+          var bar = React.render(<App.Foo.Bar.Baz/>);
+          return bar;
+        };
+        foo()
+      `,
+    },
+    {
+      code: /* tsx */ `
+        var object;
+        React.render(<object.Tag />);
+      `,
+    },
+    {
+      code: /* tsx */ `
+        var object;
+        React.render(<object.tag />);
+      `,
+    },
+  ],
+});

packages/plugins/eslint-plugin-react-x/src/rules/jsx-uses-vars.ts

@@ -0,0 +1,46 @@
+import { O } from "@eslint-react/tools";
+import type { TSESTree } from "@typescript-eslint/types";
+import { AST_NODE_TYPES } from "@typescript-eslint/types";
+import type { CamelCase } from "string-ts";
+
+import { createRule } from "../utils";
+
+export const RULE_NAME = "jsx-uses-vars";
+
+export type MessageID = CamelCase<typeof RULE_NAME>;
+
+export default createRule<[], MessageID>({
+  meta: {
+    type: "problem",
+    docs: {
+      // eslint-disable-next-line eslint-plugin/require-meta-docs-description
+      description: "a helper rule to mark variables as used",
+    },
+    messages: {
+      jsxUsesVars: "",
+    },
+    schema: [],
+  },
+  name: RULE_NAME,
+  create(context) {
+    function getName(node: TSESTree.Node): O.Option<string> {
+      switch (node.type) {
+        case AST_NODE_TYPES.JSXIdentifier:
+          return O.some(node.name);
+        case AST_NODE_TYPES.JSXMemberExpression:
+          return getName(node.object);
+        default:
+          return O.none();
+      }
+    }
+    return {
+      JSXOpeningElement(node) {
+        if (node.name.type === AST_NODE_TYPES.JSXIdentifier && /^[a-z]/u.test(node.name.name)) return;
+        O.map(getName(node.name), (name) => {
+          context.sourceCode.markVariableAsUsed(name, node);
+        });
+      },
+    };
+  },
+  defaultOptions: [],
+});

packages/plugins/eslint-plugin/src/index.ts

@@ -15,7 +15,10 @@ import { padKeysLeft } from "./utils";
 
 const allPreset = {
   // Part: Core
+  "avoid-shorthand-boolean": "warn",
+  "avoid-shorthand-fragment": "warn",
   "ensure-forward-ref-using-ref": "warn",
+  "jsx-uses-vars": "warn",
   "no-access-state-in-setstate": "error",
   "no-array-index-key": "warn",
   "no-children-count": "warn",
@@ -58,9 +61,6 @@ const allPreset = {
   // "prefer-read-only-props": "warn", // This rule requires type information
   "prefer-shorthand-boolean": "warn",
   "prefer-shorthand-fragment": "warn",
-  // eslint-disable-next-line perfectionist/sort-objects
-  "avoid-shorthand-boolean": "warn",
-  "avoid-shorthand-fragment": "warn",
 
   // Part: DOM
   "dom/no-children-in-void-dom-elements": "warn",
@@ -96,9 +96,10 @@ const allPreset = {
 } as const satisfies RulePreset;
 
 const corePreset = {
+  "ensure-forward-ref-using-ref": "warn",
   // "avoid-shorthand-boolean": "warn",
   // "avoid-shorthand-fragment": "warn",
-  "ensure-forward-ref-using-ref": "warn",
+  "jsx-uses-vars": "warn",
   "no-access-state-in-setstate": "error",
   "no-array-index-key": "warn",
   "no-children-count": "warn",

packages/tools/package.json

@@ -42,7 +42,7 @@
     "publish": "pnpm run build && pnpm run lint:publish"
   },
   "devDependencies": {
-    "effect": "^3.10.4",
+    "effect": "^3.10.5",
     "tsup": "^8.3.5"
   }
 }