From ef173f778cc676e33da179ca7b8798bd16ce524f Mon Sep 17 00:00:00 2001
From: cexbrayat <cedric@ninja-squad.com>
Date: Thu, 16 Apr 2020 18:54:58 +0200
Subject: [PATCH] feat: properly type mount

This offers proper typings for the props given in the mounting options.
---
 src/mount.ts             | 46 +++++++++++++++++++-----
 test-dts/index.d-test.ts | 78 ++++++++++++++++++++++++++++++++++++----
 2 files changed, 108 insertions(+), 16 deletions(-)

diff --git a/src/mount.ts b/src/mount.ts
index a125b86d4..a2ba87fa3 100644
--- a/src/mount.ts
+++ b/src/mount.ts
@@ -10,7 +10,11 @@ import {
   Directive,
   Component,
   reactive,
-  ComponentPublicInstance
+  ComponentPublicInstance,
+  ComponentOptionsWithObjectProps,
+  ComponentOptionsWithArrayProps,
+  ComponentOptionsWithoutProps,
+  ExtractPropTypes
 } from 'vue'
 
 import { createWrapper, VueWrapper } from './vue-wrapper'
@@ -25,9 +29,9 @@ import { stubComponents } from './stubs'
 
 type Slot = VNode | string | { render: Function }
 
-interface MountingOptions {
+interface MountingOptions<Props> {
   data?: () => Record<string, unknown>
-  props?: Record<string, any>
+  props?: Props
   slots?: {
     default?: Slot
     [key: string]: Slot
@@ -45,17 +49,41 @@ interface MountingOptions {
   stubs?: Record<string, any>
 }
 
-export function mount<TestedComponent extends ComponentPublicInstance>(
+// Component declared with defineComponent
+export function mount<
+  TestedComponent extends ComponentPublicInstance,
+  PublicProps extends TestedComponent['$props']
+>(
   originalComponent: new () => TestedComponent,
-  options?: MountingOptions
+  options?: MountingOptions<PublicProps>
 ): VueWrapper<TestedComponent>
-export function mount(
-  originalComponent: Component,
-  options?: MountingOptions
+// Component declared with { props: { ... } }
+export function mount<
+  TestedComponent extends ComponentOptionsWithObjectProps,
+  PublicProps extends ExtractPropTypes<TestedComponent['props']>
+>(
+  originalComponent: TestedComponent,
+  options?: MountingOptions<PublicProps>
+): VueWrapper<any>
+// Component declared with { props: [] }
+export function mount<
+  TestedComponent extends ComponentOptionsWithArrayProps,
+  PublicProps extends Record<string, any>
+>(
+  originalComponent: TestedComponent,
+  options?: MountingOptions<PublicProps>
+): VueWrapper<any>
+// Component declared with no props
+export function mount<
+  TestedComponent extends ComponentOptionsWithoutProps,
+  PublicProps extends Record<string, any>
+>(
+  originalComponent: TestedComponent,
+  options?: MountingOptions<PublicProps>
 ): VueWrapper<any>
 export function mount(
   originalComponent: any,
-  options?: MountingOptions
+  options?: MountingOptions<any>
 ): VueWrapper<any> {
   const component = { ...originalComponent }
 
diff --git a/test-dts/index.d-test.ts b/test-dts/index.d-test.ts
index c454c832e..e5a2daea6 100644
--- a/test-dts/index.d-test.ts
+++ b/test-dts/index.d-test.ts
@@ -1,23 +1,87 @@
-import { expectType } from 'tsd'
+import { expectError, expectType } from 'tsd'
 import { defineComponent } from 'vue'
 import { mount } from '../src'
 
-const App = defineComponent({
+const AppWithDefine = defineComponent({
   props: {
-    a: String
+    a: {
+      type: String,
+      required: true
+    }
   },
   template: ''
 })
 
-let wrapper = mount(App)
+// accept props
+let wrapper = mount(AppWithDefine, {
+  props: { a: 'Hello' }
+})
+// vm is properly typed
 expectType<string>(wrapper.vm.a)
 
-const AppWithoutDefine = {
+// can receive extra props
+mount(AppWithDefine, {
+  props: { a: 'Hello', b: 2 }
+})
+
+// wrong prop type should not compile
+expectError(
+  mount(AppWithDefine, {
+    props: { a: 2 }
+  })
+)
+
+const AppWithProps = {
   props: {
-    a: String
+    a: {
+      type: String,
+      required: true
+    }
   },
   template: ''
 }
 
-wrapper = mount(AppWithoutDefine)
+// accept props
+wrapper = mount(AppWithProps, {
+  props: { a: 'Hello' }
+})
+// vm is properly typed
 expectType<string>(wrapper.vm.a)
+
+// can receive extra props
+mount(AppWithProps, {
+  props: { a: 'Hello', b: 2 }
+})
+
+// wrong prop type should not compile
+expectError(
+  mount(AppWithProps, {
+    props: { a: 2 }
+  })
+)
+
+const AppWithArrayProps = {
+  props: ['a'],
+  template: ''
+}
+
+// accept props
+wrapper = mount(AppWithArrayProps, {
+  props: { a: 'Hello' }
+})
+// vm is properly typed
+expectType<string>(wrapper.vm.a)
+
+// can receive extra props
+mount(AppWithArrayProps, {
+  props: { a: 'Hello', b: 2 }
+})
+
+const AppWithoutProps = {
+  template: ''
+}
+
+// can receive extra props
+wrapper = mount(AppWithoutProps, {
+  props: { b: 'Hello' }
+})