[FIX] component: improve unmount/remount behaviour

src/component/component.ts

@@ -278,19 +278,22 @@ export class Component<T extends Env, Props extends {}, State extends {}> {
    *
    * Note that a component can be mounted an unmounted several times
    */
-  async mount(target: HTMLElement): Promise<void> {
-    if (this.__owl__.isMounted) {
+  async mount(target: HTMLElement, renderBeforeRemount: boolean = false): Promise<void> {
+    const __owl__ = this.__owl__;
+    if (__owl__.isMounted) {
       return;
     }
-    if (!this.__owl__.vnode) {
-      // we use the fact that renderId === 1 as a way to determine that the
-      // component is mounted for the first time
+    if (!__owl__.vnode) {
       const vnode = await this.__prepare();
-      if (this.__owl__.isDestroyed) {
+      if (__owl__.isDestroyed) {
         // component was destroyed before we get here...
         return;
       }
       this.__patch(vnode);
+    } else if (renderBeforeRemount) {
+      const patchQueue = [];
+      await this.__render(false, patchQueue, undefined, undefined);
+      this.__applyPatchQueue(<any[]>patchQueue);
     }
     target.appendChild(this.el!);
 
@@ -561,9 +564,7 @@ export class Component<T extends Env, Props extends {}, State extends {}> {
     const __owl__ = this.__owl__;
     const promises: Promise<void>[] = [];
     const patch: any[] = [this];
-    if (__owl__.isMounted) {
-      patchQueue.push(patch);
-    }
+    patchQueue.push(patch);
     if (__owl__.observer) {
       __owl__.observer.allowMutations = false;
     }

src/component/directive.ts

@@ -454,7 +454,14 @@ QWeb.addDirective({
 
     ctx.addElse();
     // need to update component
-    const patchQueueCode = async ? `patchQueue${componentID}` : "extra.patchQueue";
+    let patchQueueCode = async ? `patchQueue${componentID}` : "extra.patchQueue";
+    if (keepAlive) {
+        // if we have t-keepalive="1", the component could be unmounted, but then
+        // we __updateProps is called.  This is ok, but we do not want to call
+        // the willPatch/patched hooks of the component in this case, so we
+        // disable the patch queue
+        patchQueueCode = `w${componentID}.__owl__.isMounted ? ${patchQueueCode} : []`;
+    }
     if (QWeb.dev) {
       ctx.addLine(`utils.validateProps(w${componentID}.constructor, props${componentID})`);
     }