From f39eb6e981d279c24fa3bd831993c0e61500be1e Mon Sep 17 00:00:00 2001
From: Gypsophyllite <50662386+Gypsophyllite@users.noreply.github.com>
Date: Wed, 17 May 2023 19:56:47 +0800
Subject: [PATCH] fix(nuxt): infer `useFetch` method when generic is passed
 (#20797)

---
 packages/nuxt/src/app/composables/fetch.ts       | 8 ++++----
 test/fixtures/basic/server/api/hey/index.post.ts | 3 +++
 test/fixtures/basic/types.ts                     | 4 ++++
 3 files changed, 11 insertions(+), 4 deletions(-)
 create mode 100644 test/fixtures/basic/server/api/hey/index.post.ts

diff --git a/packages/nuxt/src/app/composables/fetch.ts b/packages/nuxt/src/app/composables/fetch.ts
index fe487dcecd..c06271cb43 100644
--- a/packages/nuxt/src/app/composables/fetch.ts
+++ b/packages/nuxt/src/app/composables/fetch.ts
@@ -31,7 +31,7 @@ export function useFetch<
   ResT = void,
   ErrorT = FetchError,
   ReqT extends NitroFetchRequest = NitroFetchRequest,
-  Method extends AvailableRouterMethod<ReqT> = 'get' extends AvailableRouterMethod<ReqT> ? 'get' : AvailableRouterMethod<ReqT>,
+  Method extends AvailableRouterMethod<ReqT> = ResT extends void ? 'get' extends AvailableRouterMethod<ReqT> ? 'get' : AvailableRouterMethod<ReqT> : AvailableRouterMethod<ReqT>,
   _ResT = ResT extends void ? FetchResult<ReqT, Method> : ResT,
   DataT = _ResT,
   PickKeys extends KeysOf<DataT> = KeysOf<DataT>
@@ -43,7 +43,7 @@ export function useFetch<
   ResT = void,
   ErrorT = FetchError,
   ReqT extends NitroFetchRequest = NitroFetchRequest,
-  Method extends AvailableRouterMethod<ReqT> = 'get' extends AvailableRouterMethod<ReqT> ? 'get' : AvailableRouterMethod<ReqT>,
+  Method extends AvailableRouterMethod<ReqT> = ResT extends void ? 'get' extends AvailableRouterMethod<ReqT> ? 'get' : AvailableRouterMethod<ReqT> : AvailableRouterMethod<ReqT>,
   _ResT = ResT extends void ? FetchResult<ReqT, Method> : ResT,
   DataT = _ResT,
   PickKeys extends KeysOf<DataT> = KeysOf<DataT>
@@ -124,7 +124,7 @@ export function useLazyFetch<
   ResT = void,
   ErrorT = FetchError,
   ReqT extends NitroFetchRequest = NitroFetchRequest,
-  Method extends AvailableRouterMethod<ReqT> = 'get' extends AvailableRouterMethod<ReqT> ? 'get' : AvailableRouterMethod<ReqT>,
+  Method extends AvailableRouterMethod<ReqT> = ResT extends void ? 'get' extends AvailableRouterMethod<ReqT> ? 'get' : AvailableRouterMethod<ReqT> : AvailableRouterMethod<ReqT>,
   _ResT = ResT extends void ? FetchResult<ReqT, Method> : ResT,
   DataT = _ResT,
   PickKeys extends KeysOf<DataT> = KeysOf<DataT>
@@ -136,7 +136,7 @@ export function useLazyFetch<
   ResT = void,
   ErrorT = FetchError,
   ReqT extends NitroFetchRequest = NitroFetchRequest,
-  Method extends AvailableRouterMethod<ReqT> = 'get' extends AvailableRouterMethod<ReqT> ? 'get' : AvailableRouterMethod<ReqT>,
+  Method extends AvailableRouterMethod<ReqT> = ResT extends void ? 'get' extends AvailableRouterMethod<ReqT> ? 'get' : AvailableRouterMethod<ReqT> : AvailableRouterMethod<ReqT>,
   _ResT = ResT extends void ? FetchResult<ReqT, Method> : ResT,
   DataT = _ResT,
   PickKeys extends KeysOf<DataT> = KeysOf<DataT>
diff --git a/test/fixtures/basic/server/api/hey/index.post.ts b/test/fixtures/basic/server/api/hey/index.post.ts
new file mode 100644
index 0000000000..b09599aed3
--- /dev/null
+++ b/test/fixtures/basic/server/api/hey/index.post.ts
@@ -0,0 +1,3 @@
+export default defineEventHandler(() => ({
+  method: 'post' as const
+}))
diff --git a/test/fixtures/basic/types.ts b/test/fixtures/basic/types.ts
index 4caf8a256f..1b61186a60 100644
--- a/test/fixtures/basic/types.ts
+++ b/test/fixtures/basic/types.ts
@@ -17,6 +17,7 @@ describe('API routes', () => {
     expectTypeOf($fetch('/api/hello')).toEqualTypeOf<Promise<string>>()
     expectTypeOf($fetch('/api/hey')).toEqualTypeOf<Promise<{ foo: string, baz: string }>>()
     expectTypeOf($fetch('/api/hey', { method: 'get' })).toEqualTypeOf<Promise<{ foo: string, baz: string }>>()
+    expectTypeOf($fetch('/api/hey', { method: 'post' })).toEqualTypeOf<Promise<{ method: 'post' }>>()
     // @ts-expect-error not a valid method
     expectTypeOf($fetch('/api/hey', { method: 'patch ' })).toEqualTypeOf<Promise<{ foo: string, baz: string }>>()
     expectTypeOf($fetch('/api/union')).toEqualTypeOf<Promise<{ type: 'a', foo: string } | { type: 'b', baz: string }>>()
@@ -51,8 +52,10 @@ describe('API routes', () => {
   it('works with useFetch', () => {
     expectTypeOf(useFetch('/api/hello').data).toEqualTypeOf<Ref<string | null>>()
     expectTypeOf(useFetch('/api/hey').data).toEqualTypeOf<Ref<{ foo: string, baz: string } | null>>()
+    // @ts-expect-error TODO: remove when fixed upstream: https://github.com/unjs/nitro/pull/1247
     expectTypeOf(useFetch('/api/hey', { method: 'GET' }).data).toEqualTypeOf<Ref<{ foo: string, baz: string } | null>>()
     expectTypeOf(useFetch('/api/hey', { method: 'get' }).data).toEqualTypeOf<Ref<{ foo: string, baz: string } | null>>()
+    expectTypeOf(useFetch('/api/hey', { method: 'post' }).data).toEqualTypeOf<Ref<{ method: 'post' } | null>>()
     // @ts-expect-error not a valid method
     useFetch('/api/hey', { method: 'PATCH' })
     expectTypeOf(useFetch('/api/hey', { pick: ['baz'] }).data).toEqualTypeOf<Ref<{ baz: string } | null>>()
@@ -60,6 +63,7 @@ describe('API routes', () => {
     expectTypeOf(useFetch('/api/union', { pick: ['type'] }).data).toEqualTypeOf<Ref<{ type: 'a' } | { type: 'b' } | null>>()
     expectTypeOf(useFetch('/api/other').data).toEqualTypeOf<Ref<unknown>>()
     expectTypeOf(useFetch<TestResponse>('/test').data).toEqualTypeOf<Ref<TestResponse | null>>()
+    expectTypeOf(useFetch<TestResponse>('/test', { method: 'POST' }).data).toEqualTypeOf<Ref<TestResponse | null>>()
 
     expectTypeOf(useFetch('/error').error).toEqualTypeOf<Ref<FetchError | null>>()
     expectTypeOf(useFetch<any, string>('/error').error).toEqualTypeOf<Ref<string | null>>()