fix(eslint-plugin-query): fix no-void-query-fn false positive on enums for TS 6 (TanStack#10460)

Co-authored-by: Dominik Dorfmeister 🔮 <office@dorfmeister.cc>

Author: park-jemin

.changeset/no-void-query-fn-ts6-enum.md

@@ -0,0 +1,5 @@
+---
+'@tanstack/eslint-plugin-query': patch
+---
+
+fix(eslint-plugin-query): fix `no-void-query-fn` false positive on enum returns for typescript 6.

packages/eslint-plugin-query/src/__tests__/no-void-query-fn.test.ts

@@ -267,6 +267,84 @@ ruleTester.run('no-void-query-fn', rule, {
         })
       `,
     },
+    {
+      name: 'queryFn returns a numeric enum member',
+      code: normalizeIndent`
+        import { useQuery } from '@tanstack/react-query'
+
+        enum ExampleEnum {
+          A,
+          B,
+        }
+
+        function Component() {
+          const query = useQuery({
+            queryKey: ['test'],
+            queryFn: () => ExampleEnum.A,
+          })
+          return null
+        }
+      `,
+    },
+    {
+      name: 'queryFn returns a string enum member',
+      code: normalizeIndent`
+        import { useQuery } from '@tanstack/react-query'
+
+        enum StringEnum {
+          Foo = 'foo',
+          Bar = 'bar',
+        }
+
+        function Component() {
+          const query = useQuery({
+            queryKey: ['test'],
+            queryFn: () => StringEnum.Foo,
+          })
+          return null
+        }
+      `,
+    },
+    {
+      name: 'async queryFn returns a numeric enum member',
+      code: normalizeIndent`
+        import { useQuery } from '@tanstack/react-query'
+
+        enum Status {
+          Active,
+          Inactive,
+        }
+
+        function Component() {
+          const query = useQuery({
+            queryKey: ['test'],
+            queryFn: async () => {
+              return Status.Active
+            },
+          })
+          return null
+        }
+      `,
+    },
+    {
+      name: 'queryFn returns a const enum member',
+      code: normalizeIndent`
+        import { useQuery } from '@tanstack/react-query'
+
+        const enum Direction {
+          Up = 'UP',
+          Down = 'DOWN',
+        }
+
+        function Component() {
+          const query = useQuery({
+            queryKey: ['test'],
+            queryFn: () => Direction.Up,
+          })
+          return null
+        }
+      `,
+    },
   ],
   invalid: [
     {

packages/eslint-plugin-query/src/rules/no-void-query-fn/no-void-query-fn.rule.ts

@@ -5,11 +5,6 @@ import { getDocsUrl } from '../../utils/get-docs-url'
 import type { ParserServicesWithTypeInformation } from '@typescript-eslint/utils'
 import type { ExtraRuleDocs } from '../../types'
 
-const TypeFlags = {
-  Void: 16384,
-  Undefined: 32768,
-} as const
-
 export const name = 'no-void-query-fn'
 
 const createRule = ESLintUtils.RuleCreator<ExtraRuleDocs>(getDocsUrl)
@@ -87,5 +82,6 @@ function isIllegalReturn(checker: TypeChecker, type: Type): boolean {
     return awaited.types.some((t) => isIllegalReturn(checker, t))
   }
 
-  return awaited.flags & (TypeFlags.Void | TypeFlags.Undefined) ? true : false
+  const typeString = checker.typeToString(awaited)
+  return typeString === 'void' || typeString === 'undefined'
 }