feat(runtime-dom): support using mount target innerHTML as template

packages/runtime-core/src/apiApp.ts

@@ -18,7 +18,7 @@ export interface App<HostElement = any> {
   directive(name: string, directive: Directive): this
   mount(
     rootComponent: Component,
-    rootContainer: HostElement,
+    rootContainer: HostElement | string,
     rootProps?: Data
   ): ComponentPublicInstance
   provide<T>(key: InjectionKey<T> | string, value: T): void
@@ -141,7 +141,7 @@ export function createAppAPI<HostNode, HostElement>(
 
       mount(
         rootComponent: Component,
-        rootContainer: string | HostElement,
+        rootContainer: HostElement,
         rootProps?: Data
       ): any {
         if (!isMounted) {

packages/runtime-core/src/createRenderer.ts

@@ -123,7 +123,7 @@ export interface RendererOptions<HostNode = any, HostElement = any> {
 
 export type RootRenderFunction<HostNode, HostElement> = (
   vnode: VNode<HostNode, HostElement> | null,
-  dom: HostElement | string
+  dom: HostElement
 ) => void
 
 /**
@@ -1858,19 +1858,12 @@ export function createRenderer<
     }
   }
 
-  function render(vnode: HostVNode | null, rawContainer: HostElement | string) {
-    let container: any = rawContainer
-    if (isString(container)) {
-      container = hostQuerySelector(container)
-      if (!container) {
-        if (__DEV__) {
-          warn(
-            `Failed to locate root container: ` + `querySelector returned null.`
-          )
-        }
-        return
-      }
+  const render: RootRenderFunction<
+    HostNode,
+    HostElement & {
+      _vnode: HostVNode | null
     }
+  > = (vnode, container) => {
     if (vnode == null) {
       if (container._vnode) {
         unmount(container._vnode, null, null, true)

packages/runtime-dom/src/index.ts

@@ -1,27 +1,54 @@
-import { createRenderer } from '@vue/runtime-core'
+import { createRenderer, warn } from '@vue/runtime-core'
 import { nodeOps } from './nodeOps'
 import { patchProp } from './patchProp'
 // Importing from the compiler, will be tree-shaken in prod
 import { isHTMLTag, isSVGTag } from '@vue/compiler-dom'
+import { isFunction, isString } from '@vue/shared'
 
-const { render, createApp } = createRenderer<Node, Element>({
+const { render, createApp: baseCreateApp } = createRenderer<Node, Element>({
   patchProp,
   ...nodeOps
 })
 
-const wrappedCreateApp = () => {
-  const app = createApp()
-  // inject `isNativeTag` dev only
+const createApp = () => {
+  const app = baseCreateApp()
+
+  if (__DEV__) {
+    // Inject `isNativeTag`
+    // this is used for component name validation (dev only)
     Object.defineProperty(app.config, 'isNativeTag', {
       value: (tag: string) => isHTMLTag(tag) || isSVGTag(tag),
       writable: false
     })
+  }
+
+  const mount = app.mount
+  app.mount = (component, container, props): any => {
+    if (isString(container)) {
+      container = document.querySelector(container)!
+      if (!container) {
+        __DEV__ &&
+          warn(`Failed to mount app: mount target selector returned null.`)
+        return
+      }
+    }
+    if (
+      __RUNTIME_COMPILE__ &&
+      !isFunction(component) &&
+      !component.render &&
+      !component.template
+    ) {
+      component.template = container.innerHTML
+    }
+    // clear content before mounting
+    container.innerHTML = ''
+    return mount(component, container, props)
+  }
+
   return app
 }
 
-const exportedCreateApp = __DEV__ ? wrappedCreateApp : createApp
-
-export { render, exportedCreateApp as createApp }
+export { render, createApp }
 
 // DOM-only runtime helpers
 export {