fix:fix conditional Typing in useSWRMutation to Allow Optional ExtraA…

…rg Without Explicitly Passing Undefined (#2666)

* fix: add optional type

* fix: delete unused test

* fix: revert changes

* type: add case with optional ExtraArgs

* refactor: TriggerWithOptionalArgs -> TriggerWithOptionsArgs

mutation/src/types.ts

@@ -49,6 +49,7 @@ export type SWRMutationConfiguration<
 }
 
 type RemoveUndefined<T> = T extends undefined ? never : T
+type IsUndefinedIncluded<T> = undefined extends T ? true : false
 export interface TriggerWithArgs<
   Data = any,
   Error = any,
@@ -87,6 +88,44 @@ export interface TriggerWithArgs<
   ): Promise<Data | undefined>
 }
 
+interface TriggerWithOptionsArgs<
+  Data = any,
+  Error = any,
+  SWRMutationKey extends Key = Key,
+  ExtraArg = never
+> {
+  <SWRData = Data>(
+    extraArgument?: ExtraArg,
+    options?: SWRMutationConfiguration<
+      Data,
+      Error,
+      SWRMutationKey,
+      ExtraArg,
+      SWRData
+    >
+  ): Promise<Data>
+  <SWRData = Data>(
+    extraArgument?: ExtraArg,
+    options?: SWRMutationConfiguration<
+      Data,
+      Error,
+      SWRMutationKey,
+      ExtraArg,
+      SWRData
+    > & { throwOnError: true }
+  ): Promise<RemoveUndefined<Data>>
+  <SWRData = Data>(
+    extraArgument?: ExtraArg,
+    options?: SWRMutationConfiguration<
+      Data,
+      Error,
+      SWRMutationKey,
+      ExtraArg,
+      SWRData
+    > & { throwOnError: false }
+  ): Promise<Data | undefined>
+}
+
 export interface TriggerWithoutArgs<
   Data = any,
   Error = any,
@@ -141,6 +180,8 @@ export interface SWRMutationResponse<
    */
   trigger: [ExtraArg] extends [never]
     ? TriggerWithoutArgs<Data, Error, SWRMutationKey, ExtraArg>
+    : IsUndefinedIncluded<ExtraArg> extends true
+    ? TriggerWithOptionsArgs<Data, Error, SWRMutationKey, ExtraArg>
     : TriggerWithArgs<Data, Error, SWRMutationKey, ExtraArg>
   /**
    * Function to reset the mutation state (`data`, `error`, and `isMutating`).

test/type/trigger.ts

@@ -114,6 +114,22 @@ export function useTestSWRMutation() {
   test()
 }
 
+export function useTestSWRMutationWithOptionalArgs() {
+  const { trigger } = useSWRMutation(
+    'key',
+    async (_, { arg }: { arg?: 'foo' }) => {
+      return arg?.toUpperCase()
+    }
+  )
+
+  const test = () => {
+    expectType<Promise<string | undefined>>(trigger('foo'))
+    expectType<Promise<string | undefined>>(trigger(undefined))
+    expectType<Promise<string | undefined>>(trigger())
+  }
+  test()
+}
+
 export function useTestSWRMutationWithSWRMutate() {
   const { mutate } = useSWR('/some/key', () => {
     return {