feat: support computed property methods

Closes #60

Author: JamieMason

src/rule.ts

@@ -85,12 +85,26 @@ export const preferArrowFunctions = createRule<Options, MessageId>({
           });
         }
       },
-      ':matches(ClassProperty, MethodDefinition, Property)[key.name][value.type="FunctionExpression"][kind!=/^(get|set|constructor)$/]':
+      ':matches(ClassProperty, MethodDefinition, Property)[value.type="FunctionExpression"][kind!=/^(get|set|constructor)$/]':
         (node: TSESTree.MethodDefinition | TSESTree.Property) => {
           const fn = node.value;
           if (guard.isSafeTransformation(fn) && (!guard.isWithinClassBody(fn) || options.classPropertiesAllowed)) {
-            const name = 'name' in node.key ? node.key.name : '';
-            const propName = node.key.type === AST_NODE_TYPES.PrivateIdentifier ? `#${name}` : name;
+            let propName: string;
+
+            if (node.key.type === AST_NODE_TYPES.PrivateIdentifier) {
+              const name = 'name' in node.key ? node.key.name : '';
+              propName = `#${name}`;
+            } else if (node.computed) {
+              // For computed properties like [foo], [Symbol.iterator], etc.
+              propName = `[${sourceCode.getText(node.key)}]`;
+            } else if ('name' in node.key) {
+              // For simple property names
+              propName = node.key.name;
+            } else {
+              // Fallback to source text for other cases
+              propName = sourceCode.getText(node.key);
+            }
+
             const staticModifier = 'static' in node && node.static ? 'static ' : '';
             ctx.report({
               fix: (fixer) =>

test/rule.spec.ts

@@ -513,3 +513,114 @@ describe('when file is TSX', () => {
     });
   });
 });
+
+describe('issue #60 - computed property keys should be preserved', () => {
+  describe('when computed property methods should NOT be transformed', () => {
+    ruleTester.run('prefer-arrow-functions', rule, {
+      valid: [
+        {
+          code: `const obj = {
+  [Symbol.iterator]() {
+    return this;
+  },
+};`,
+        },
+        {
+          code: `const dynamicKey = 'method';
+const obj = {
+  [dynamicKey]() {
+    console.log(this.value);
+  },
+};`,
+        },
+        {
+          code: `const obj = {
+  ['computed-key']() {
+    return arguments[0];
+  },
+};`,
+        },
+        {
+          code: `const prefix = 'handle';
+const suffix = 'Click';
+const obj = {
+  [prefix + suffix]() {
+    super.onClick();
+  },
+};`,
+        },
+      ],
+      invalid: [],
+    });
+  });
+
+  describe('when computed property methods can be safely transformed', () => {
+    ruleTester.run('prefer-arrow-functions', rule, {
+      valid: [],
+      invalid: [
+        {
+          code: `const foo = 'bar';
+export default {
+  [foo]() {
+    console.log('output');
+  },
+};`,
+          output: `const foo = 'bar';
+export default {
+  [foo]: () => {
+    console.log('output');
+  },
+};`,
+        },
+        {
+          code: `const methodName = 'getData';
+const obj = {
+  [methodName]() {
+    return 42;
+  },
+};`,
+          output: `const methodName = 'getData';
+const obj = {
+  [methodName]: () => 42,
+};`,
+        },
+        {
+          code: `const obj = {
+  ['computed-key']() {
+    return 'value';
+  },
+};`,
+          output: `const obj = {
+  ['computed-key']: () => 'value',
+};`,
+        },
+        {
+          code: `const obj = {
+  [Symbol.iterator]() {
+    return 'iterator';
+  },
+};`,
+          output: `const obj = {
+  [Symbol.iterator]: () => 'iterator',
+};`,
+        },
+        {
+          code: `const prefix = 'handle';
+const suffix = 'Click';
+const obj = {
+  [prefix + suffix]() {
+    console.log('clicked');
+  },
+};`,
+          output: `const prefix = 'handle';
+const suffix = 'Click';
+const obj = {
+  [prefix + suffix]: () => {
+    console.log('clicked');
+  },
+};`,
+        },
+      ].map(withErrors(['USE_ARROW_WHEN_FUNCTION'])),
+    });
+  });
+});