feat(eslint-plugin-react-hooks): convert to typescript and package type declarations

This change converts the eslint hooks plugin to typescript, which also allows us to include type declarations in the package, for those using [typescript eslint configs](https://eslint.org/blog/2025/01/eslint-v9.18.0-released/#stable-typescript-configuration-file-support).

Author: michaelfaith

packages/eslint-plugin-react-hooks/src/ExhaustiveDeps.ts

@@ -237,7 +237,7 @@ const rule = {
           return false;
         }
         const def = resolved.defs[0];
-        if (!def) {
+        if (def == null) {
           return false;
         }
         // Look for `let stuff = ...`
@@ -246,7 +246,7 @@ const rule = {
           return false;
         }
         let init = defNode.init;
-        if (!init) {
+        if (init == null) {
           return false;
         }
         while (init.type === 'TSAsExpression' || init.type === 'AsExpression') {
@@ -255,13 +255,13 @@ const rule = {
         // Detect primitive constants
         // const foo = 42
         let declaration = defNode.parent;
-        if (!declaration && componentScope) {
+        if (declaration == null && componentScope) {
           // This might happen if variable is declared after the callback.
           // In that case ESLint won't set up .parent refs.
           // So we'll set them up manually.
           fastFindReferenceWithParent(componentScope.block, def.node.id);
           declaration = def.node.parent;
-          if (!declaration) {
+          if (declaration == null) {
             return false;
           }
         }
@@ -406,13 +406,13 @@ const rule = {
             break;
           }
         }
-        if (!fnScope) {
+        if (fnScope == null) {
           return false;
         }
         // Does this function capture any values
         // that are in pure scopes (aka render)?
         for (const ref of fnScope.through) {
-          if (!ref.resolved) {
+          if (ref.resolved == null) {
             continue;
           }
           if (
@@ -488,7 +488,7 @@ const rule = {
             node,
             reference.identifier,
           );
-          if (!referenceNode) {
+          if (referenceNode == null) {
             continue;
           }
           const dependencyNode = getDependency(referenceNode);
@@ -525,7 +525,7 @@ const rule = {
           }
 
           const def = reference.resolved.defs[0];
-          if (!def) {
+          if (def == null) {
             continue;
           }
           // Ignore references to the function itself as it's not defined yet.
@@ -1707,7 +1707,7 @@ function scanForConstructions({
   const constructions = declaredDependencies
     .map(({key}) => {
       const ref = componentScope.variables.find(v => v.name === key);
-      if (!ref) {
+      if (ref == null) {
         return null;
       }
 

packages/eslint-plugin-react-hooks/src/RulesOfHooks.ts

@@ -147,7 +147,10 @@ const rule = {
           parent.init.callee &&
           isUseEffectEventIdentifier(parent.init.callee)
         ) {
-          for (const ref of reference.resolved?.references || []) {
+          if (reference.resolved === null) {
+            throw new Error('Unexpected null reference.resolved');
+          }
+          for (const ref of reference.resolved.references) {
             if (ref !== reference) {
               useEffectEventFunctions.add(ref.identifier);
             }
@@ -196,8 +199,10 @@ const rule = {
       // segment and reachable from every final segment.
       onCodePathEnd(codePath, codePathNode) {
         const reactHooksMap = codePathReactHooksMapStack.pop();
-        if (!reactHooksMap?.size) {
+        if (reactHooksMap?.size === 0) {
           return;
+        } else if (typeof reactHooksMap === 'undefined') {
+          throw new Error('Unexpected undefined reactHooksMap');
         }
 
         // All of the segments which are cyclic are recorded in this set.

packages/eslint-plugin-react-hooks/src/index.ts

@@ -8,8 +8,6 @@ import RulesOfHooks from './RulesOfHooks';
 import ExhaustiveDeps from './ExhaustiveDeps';
 import type {ESLint, Linter, Rule} from 'eslint';
 
-const packageJson: {name: string; version: string} = require('../package.json');
-
 // All rules
 const rules = {
   'rules-of-hooks': RulesOfHooks,
@@ -30,7 +28,9 @@ const legacyRecommendedConfig = {
 
 // Plugin object
 const plugin = {
-  meta: {name: packageJson.name, version: packageJson.version},
+  // TODO: Make this more dynamic to populate version from package.json.
+  // This can be done by injecting at build time, since importing the package.json isn't an option in Meta
+  meta: {name: 'eslint-plugin-react-hooks'},
   rules,
   configs: {
     /** Legacy recommended config, to be used with rc-based configurations */
@@ -55,8 +55,10 @@ const plugin = {
   },
 } satisfies ESLint.Plugin;
 
-// These exports are for backwards compatibility with eslint versions before v9
 const configs = plugin.configs;
-export {configs, rules};
+const meta = plugin.meta;
+export {configs, meta, rules};
 
-export default plugin;
+// TODO: If the plugin is ever updated to be pure ESM and drops support for rc-based configs, then it should be exporting the plugin as default
+// instead of individual named exports.
+// export default plugin;