feat(types): add asyncData return types to component instance type (#9239)

Co-authored-by: Daniel Roe <daniel@roe.dev>

packages/types/app/vue.d.ts

@@ -5,14 +5,32 @@
 import Vue from 'vue'
 import { MetaInfo } from 'vue-meta'
 import { Route } from 'vue-router'
+import { RecordPropsDefinition, PropsDefinition, ComponentOptions } from 'vue/types/options'
+import { CombinedVueInstance, ExtendedVue } from 'vue/types/vue'
 import { NuxtRuntimeConfig } from '../config/runtime'
 import { Context, Middleware, Transition, NuxtApp } from './index'
 
+// https://github.com/vuejs/vue/blob/dev/types/options.d.ts#L63-L66
+type DefaultData<V> = object | ((this: V) => object)
+type DefaultProps = Record<string, any>
+type DefaultMethods<V> = { [key: string]: (this: V, ...args: any[]) => any }
+type DefaultComputed = { [key: string]: any }
+type DefaultAsyncData<V> = ((this: V, context: Context) => Promise<object | void> | object | void)
+
 declare module 'vue/types/options' {
-  // eslint-disable-next-line no-unused-vars,@typescript-eslint/no-unused-vars
+  interface ComponentOptions<
-  interface ComponentOptions<V extends Vue> {
+    V extends Vue,
+    /* eslint-disable no-unused-vars,@typescript-eslint/no-unused-vars */
+    Data = DefaultData<V>,
+    Methods = DefaultMethods<V>,
+    Computed = DefaultComputed,
+    PropsDef = PropsDefinition<DefaultProps>,
+    Props = DefaultProps,
+    /* eslint-enable no-unused-vars,@typescript-eslint/no-unused-vars */
+    AsyncData = DefaultAsyncData<V>
+  > {
     // eslint-disable-next-line @typescript-eslint/ban-types
-    asyncData?(ctx: Context): Promise<object | void> | object | void
+    asyncData?: AsyncData
     fetch?(ctx: Context): Promise<void> | void
     fetchKey?: string | ((getKey: (id: string) => number) => string)
     fetchDelay?: number
@@ -30,6 +48,59 @@ declare module 'vue/types/options' {
   }
 }
 
+type DataDef<Data, Props, V> = Data | ((this: Readonly<Props> & V) => Data)
+type Awaited<T> = T extends PromiseLike<infer U> ? Awaited<U> : T
+type Merged<Data, AsyncData> = {
+  [key in keyof Data | keyof AsyncData]: key extends keyof Data ? key extends keyof AsyncData ? NonNullable<Data[key]> | AsyncData[key] : Data[key] : key extends keyof AsyncData ? AsyncData[key] : never
+}
+
+type ThisTypedComponentOptionsWithArrayPropsAndAsyncData<
+  V extends Vue,
+  Data,
+  Methods,
+  Computed,
+  PropNames extends string,
+  AsyncData
+> = object &
+  ComponentOptions<
+    V,
+    DataDef<Data, Record<PropNames, any>, V>,
+    Methods,
+    Computed,
+    PropNames[],
+    Record<PropNames, any>,
+    DataDef<AsyncData, PropNames, V>
+  > &
+  ThisType<
+    CombinedVueInstance<
+      V,
+      Merged<Data, Awaited<AsyncData>>,
+      Methods,
+      Computed,
+      Readonly<Record<PropNames, any>>
+    >
+  >
+export type ThisTypedComponentOptionsWithRecordPropsAndAsyncData<
+  V extends Vue,
+  Data,
+  Methods,
+  Computed,
+  Props,
+  AsyncData
+> = object &
+  ComponentOptions<
+    V,
+    DataDef<Data, Props, V>,
+    Methods,
+    Computed,
+    RecordPropsDefinition<Props>,
+    Props,
+    DataDef<AsyncData, Props, V>
+> &
+  ThisType<
+    CombinedVueInstance<V, Merged<Data, Awaited<AsyncData>>, Methods, Computed, Readonly<Props>>
+  >
+
 declare module 'vue/types/vue' {
   interface Vue {
     $config: NuxtRuntimeConfig
@@ -41,4 +112,26 @@ declare module 'vue/types/vue' {
       timestamp: number
     }
   }
+  interface VueConstructor<V extends Vue> {
+    extend<Data, Methods, Computed, PropNames extends string, AsyncData>(
+      options?: ThisTypedComponentOptionsWithArrayPropsAndAsyncData<
+        V,
+        Data,
+        Methods,
+        Computed,
+        PropNames,
+        AsyncData
+      >
+    ): ExtendedVue<V, Data, Methods, Computed, Record<PropNames, any>>
+    extend<Data, Methods, Computed, Props, AsyncData>(
+      options?: ThisTypedComponentOptionsWithRecordPropsAndAsyncData<
+        V,
+        Data,
+        Methods,
+        Computed,
+        Props,
+        AsyncData
+      >
+    ): ExtendedVue<V, Data, Methods, Computed, Props>
+  }
 }