fix: change duplicate installation from error to warn, close #631

src/install.ts

@@ -1,6 +1,6 @@
 import type { VueConstructor } from 'vue'
 import { AnyObject } from './types/basic'
-import { hasSymbol, hasOwn, isPlainObject, assert, warn } from './utils'
+import { hasSymbol, hasOwn, isPlainObject, warn } from './utils'
 import { isRef } from './reactivity'
 import { setVueConstructor, isVueRegistered } from './runtimeContext'
 import { mixin } from './mixin'
@@ -42,9 +42,8 @@ function mergeData(from: AnyObject, to: AnyObject): Object {
 export function install(Vue: VueConstructor) {
   if (isVueRegistered(Vue)) {
     if (__DEV__) {
-      assert(
-        false,
-        'already installed. Vue.use(VueCompositionAPI) should be called only once.'
+      warn(
+        '[vue-composition-api] already installed. Vue.use(VueCompositionAPI) should be called only once.'
       )
     }
     return
@@ -53,10 +52,12 @@ export function install(Vue: VueConstructor) {
   if (__DEV__) {
     if (Vue.version) {
       if (Vue.version[0] !== '2' || Vue.version[1] !== '.') {
-        assert(false, `only works with Vue 2, v${Vue.version} found.`)
+        warn(
+          `[vue-composition-api] only works with Vue 2, v${Vue.version} found.`
+        )
       }
     } else {
-      warn('Vue version not found')
+      warn('[vue-composition-api] no Vue version found')
     }
   }
 

src/runtimeContext.ts

@@ -61,7 +61,7 @@ export function getRegisteredVueOrDefault(): VueConstructor {
 export function setVueConstructor(Vue: VueConstructor) {
   // @ts-ignore
   if (__DEV__ && vueConstructor && Vue.__proto__ !== vueConstructor.__proto__) {
-    warn('Another instance of vue installed')
+    warn('[vue-composition-api] another instance of Vue installed')
   }
   vueConstructor = Vue
   Object.defineProperty(Vue, PluginInstalledFlag, {

src/utils/utils.ts

@@ -45,7 +45,9 @@ export function hasOwn(obj: Object, key: string): boolean {
 }
 
 export function assert(condition: any, msg: string) {
-  if (!condition) throw new Error(`[vue-composition-api] ${msg}`)
+  if (!condition) {
+    throw new Error(`[vue-composition-api] ${msg}`)
+  }
 }
 
 export function isPrimitive(value: any): boolean {

test/use.spec.ts

@@ -13,7 +13,9 @@ describe('use', () => {
     const localVueTwo = createLocalVue()
     localVueTwo.use(CompositionApi)
 
-    expect('Another instance of vue installed').not.toHaveBeenWarned()
+    expect(
+      '[vue-composition-api] another instance of Vue installed'
+    ).not.toHaveBeenWarned()
   })
 
   it('should warn install in multiple vue', () => {
@@ -28,26 +30,30 @@ describe('use', () => {
 
       // @ts-ignore
       CompositionApi.install(fakeVue)
-      expect('Another instance of vue installed').toHaveBeenWarned()
+      expect(
+        '[vue-composition-api] another instance of Vue installed'
+      ).toHaveBeenWarned()
     } finally {
       Vue.use(CompositionApi)
-      expect('Another instance of vue installed').toHaveBeenWarned()
+      expect(
+        '[vue-composition-api] another instance of Vue installed'
+      ).toHaveBeenWarned()
     }
   })
 
   it('should warn installing multiple times', () => {
     const localVueOne = createLocalVue()
     localVueOne.use(CompositionApi)
 
-    expect(() => {
-      // vue prevents the same plugin of being installed, this will create a new plugin instance
-      localVueOne.use({
-        install(v) {
-          CompositionApi.install(v)
-        },
-      })
-    }).toThrowError(
-      'already installed. Vue.use(VueCompositionAPI) should be called only once.'
-    )
+    // vue prevents the same plugin of being installed, this will create a new plugin instance
+    localVueOne.use({
+      install(v) {
+        CompositionApi.install(v)
+      },
+    })
+
+    expect(
+      '[vue-composition-api] already installed. Vue.use(VueCompositionAPI) should be called only once.'
+    ).toHaveBeenWarned()
   })
 })