fix: resolve conflicts with vue2 interface

src/component/componentProxy.ts

@@ -19,6 +19,7 @@ import {
 } from './componentOptions'
 import {
   ComponentInternalInstance,
+  ComponentRenderEmitFn,
   EmitFn,
   EmitsOptions,
   ObjectEmitsOptions,
@@ -67,8 +68,24 @@ export type ComponentRenderProxy<
       ? Partial<Defaults> & Omit<P & PublicProps, keyof Defaults>
       : P & PublicProps
   >
-  $attrs: Data
-  $emit: EmitFn<Emits>
+  $attrs: Record<string, string>
+  $emit: ComponentRenderEmitFn<
+    Emits,
+    keyof Emits,
+    ComponentRenderProxy<
+      P,
+      B,
+      D,
+      C,
+      M,
+      Mixin,
+      Extends,
+      Emits,
+      PublicProps,
+      Defaults,
+      MakeDefaultsOptional
+    >
+  >
 } & Readonly<P> &
   ShallowUnwrapRef<B> &
   D &

src/runtimeContext.ts

@@ -9,6 +9,7 @@ import {
   UnionToIntersection,
   isFunction,
 } from './utils'
+import Vue$1 from 'vue'
 
 let vueDependency: VueConstructor | undefined = undefined
 
@@ -121,19 +122,26 @@ export type EmitsOptions = ObjectEmitsOptions | string[]
 
 export type EmitFn<
   Options = ObjectEmitsOptions,
-  Event extends keyof Options = keyof Options
+  Event extends keyof Options = keyof Options,
+  ReturnType extends void | Vue$1 = void
 > = Options extends Array<infer V>
-  ? (event: V, ...args: any[]) => void
+  ? (event: V, ...args: any[]) => ReturnType
   : {} extends Options // if the emit is empty object (usually the default value for emit) should be converted to function
-  ? (event: string, ...args: any[]) => void
+  ? (event: string, ...args: any[]) => ReturnType
   : UnionToIntersection<
       {
         [key in Event]: Options[key] extends (...args: infer Args) => any
-          ? (event: key, ...args: Args) => void
-          : (event: key, ...args: any[]) => void
+          ? (event: key, ...args: Args) => ReturnType
+          : (event: key, ...args: any[]) => ReturnType
       }[Event]
     >
 
+export type ComponentRenderEmitFn<
+  Options = ObjectEmitsOptions,
+  Event extends keyof Options = keyof Options,
+  T extends Vue$1 | void = void
+> = EmitFn<Options, Event, T>
+
 export type Slots = Readonly<InternalSlots>
 
 export interface SetupContext<E = EmitsOptions> {

test-dts/defineComponent-vue2.d.tsx

@@ -0,0 +1,50 @@
+import {
+  defineComponent,
+  describe,
+  expectError,
+  expectType,
+  Ref,
+  ref,
+} from './index'
+import Vue from 'vue'
+
+describe('emits', () => {
+  const testComponent = defineComponent({
+    emits: {
+      click: (n: number) => typeof n === 'number',
+      input: (b: string) => b.length > 1,
+    },
+    created() {
+      this.$emit('click', 1)
+      this.$emit('click', 1).$emit('click', 1)
+      this.$emit('input', 'foo')
+      this.$emit('input', 'foo').$emit('click', 1)
+      expectType<Record<string, string>>(this.$attrs)
+      //  @ts-expect-error
+      expectError(this.$emit('input', 1).$emit('nope'))
+    },
+  })
+
+  // interface of vue2's $emit has no generics, notice that untyped types will be "event: string, ...args: any[]) => this" when using vue-class-component.
+  // but we can get correct type when we use correct params
+  // maybe we need vue 2.7 to fully support emit type
+  type VueClass<V> = { new (...args: any[]): V & Vue } & typeof Vue
+
+  function useComponentRef<T extends VueClass<Vue>>() {
+    return ref<InstanceType<T>>(undefined!) as Ref<InstanceType<T>>
+  }
+
+  const foo = useComponentRef<typeof testComponent>()
+
+  foo.value.$emit('click', 1)
+  foo.value.$emit('input', 'foo')
+  foo.value.$emit('click', 1).$emit('click', 1)
+  //  @ts-expect-error
+  expectError(foo.value.$emit('blah').$emit('click', 1))
+  //  @ts-expect-error
+  expectError(foo.value.$emit('click').$emit('click', 1))
+  //  @ts-expect-error
+  expectError(foo.value.$emit('blah').$emit('click', 1))
+  //  @ts-expect-error
+  expectError(foo.value.$emit('blah'))
+})

test-dts/tsconfig.vue3.json

@@ -4,5 +4,6 @@
     "paths": {
       "@vue/composition-api": ["../node_modules/vue3/dist/vue.d.ts"]
     }
-  }
+  },
+  "exclude": ["./defineComponent-vue2.d.tsx"]
 }

tsconfig.json

@@ -8,6 +8,7 @@
     "moduleResolution": "node",
     "skipLibCheck": true,
     "esModuleInterop": true,
+    "experimentalDecorators": true,
     "strict": true,
     "strictNullChecks": true,
     "strictFunctionTypes": true,