fix(custom-element): properly handle custom element remove then insert again

packages/runtime-dom/__tests__/customElement.spec.ts

@@ -145,6 +145,43 @@ describe('defineCustomElement', () => {
       expect(e._instance).toBeTruthy()
       expect(e.shadowRoot!.innerHTML).toBe('<div>hello</div>')
     })
+
+    // #12412
+    test('remove element with child custom element and wait fully disconnected then insert', async () => {
+      const El = defineCustomElement({
+        props: {
+          msg: String,
+        },
+        setup(props, { expose }) {
+          expose({
+            text: () => props.msg,
+          })
+          provide('context', props)
+          const context = inject('context', {}) as typeof props
+          return () => context.msg || props.msg
+        },
+      })
+      customElements.define('my-el-remove-insert-expose', El)
+      container.innerHTML = `<div><my-el-remove-insert-expose msg="msg1"><my-el-remove-insert-expose></my-el-remove-insert-expose></my-el-remove-insert-expose></div>`
+      const parent = container.children[0].children[0] as VueElement & {
+        text: () => string
+      }
+      const child = parent.children[0] as VueElement
+      parent.remove()
+      await nextTick()
+      await nextTick() // wait two ticks for disconnect
+      expect('text' in parent).toBe(false)
+      container.appendChild(parent) // should not throw Error
+      await nextTick()
+      expect(parent.text()).toBe('msg1')
+      expect(parent.shadowRoot!.textContent).toBe('msg1')
+      expect(child.shadowRoot!.textContent).toBe('msg1')
+      parent.setAttribute('msg', 'msg2')
+      await nextTick()
+      expect(parent.shadowRoot!.textContent).toBe('msg2')
+      await nextTick()
+      expect(child.shadowRoot!.textContent).toBe('msg2')
+    })
   })
 
   describe('props', () => {

packages/runtime-dom/src/apiCustomElement.ts

@@ -298,8 +298,9 @@ export class VueElement
 
     if (!this._instance) {
       if (this._resolved) {
-        this._setParent()
-        this._update()
+        // this element has been fully unmounted, should create observer again and re-mount
+        this._observe()
+        this._mount(this._def)
       } else {
         if (parent && parent._pendingResolve) {
           this._pendingResolve = parent._pendingResolve.then(() => {
@@ -330,12 +331,31 @@ export class VueElement
         }
         // unmount
         this._app && this._app.unmount()
-        if (this._instance) this._instance.ce = undefined
+        if (this._instance) {
+          const exposed = this._instance.exposed
+          if (exposed) {
+            for (const key in exposed) {
+              delete this[key as keyof this]
+            }
+          }
+          this._instance.ce = undefined
+        }
         this._app = this._instance = null
       }
     })
   }
 
+  private _observe() {
+    if (!this._ob) {
+      this._ob = new MutationObserver(mutations => {
+        for (const m of mutations) {
+          this._setAttr(m.attributeName!)
+        }
+      })
+    }
+    this._ob.observe(this, { attributes: true })
+  }
+
   /**
    * resolve inner component definition (handle possible async component)
    */
@@ -350,13 +370,7 @@ export class VueElement
     }
 
     // watch future attr changes
-    this._ob = new MutationObserver(mutations => {
-      for (const m of mutations) {
-        this._setAttr(m.attributeName!)
-      }
-    })
-
-    this._ob.observe(this, { attributes: true })
+    this._observe()
 
     const resolve = (def: InnerComponentDef, isAsync = false) => {
       this._resolved = true
@@ -430,11 +444,14 @@ export class VueElement
       if (!hasOwn(this, key)) {
         // exposed properties are readonly
         Object.defineProperty(this, key, {
+          configurable: true, // should be configurable to allow deleting when disconnected
           // unwrap ref to be consistent with public instance behavior
           get: () => unref(exposed[key]),
         })
-      } else if (__DEV__) {
-        warn(`Exposed property "${key}" already exists on custom element.`)
+      } else {
+        delete exposed[key] // delete it from exposed in case of deleting wrong exposed key when disconnected
+        if (__DEV__)
+          warn(`Exposed property "${key}" already exists on custom element.`)
       }
     }
   }
@@ -514,7 +531,7 @@ export class VueElement
         } else if (!val) {
           this.removeAttribute(hyphenate(key))
         }
-        ob && ob.observe(this, { attributes: true })
+        this._observe()
       }
     }
   }