[IMP] app: mount app in "first-child" position

We reintroduce the possibility to mount the app in first position in
a target. The option "self" has been dropped since it is now possible
for a component to have several top level nodes.

src/app.ts

@@ -1,5 +1,6 @@
 import { Component } from "./component/component";
 import { ComponentNode } from "./component/component_node";
+import { MountOptions } from "./component/fibers";
 import { Scheduler } from "./component/scheduler";
 import { TemplateSet } from "./qweb/template_helpers";
 
@@ -47,7 +48,7 @@ export class App<T extends typeof Component = any> extends TemplateSet {
     }
   }
 
-  mount(target: HTMLElement): Promise<InstanceType<T>> {
+  mount(target: HTMLElement, options?: MountOptions): Promise<InstanceType<T>> {
     if (!(target instanceof HTMLElement)) {
       throw new Error("Cannot mount component: the target is not a valid DOM element");
     }
@@ -56,7 +57,7 @@ export class App<T extends typeof Component = any> extends TemplateSet {
     }
     const node = new ComponentNode(this.Root, this.props, this);
     this.root = node;
-    return node.mountComponent(target);
+    return node.mountComponent(target, options);
   }
 
   destroy() {

src/blockdom/index.ts

@@ -23,8 +23,8 @@ export interface VNode<T = any> {
 
 export type BDom = VNode<any>;
 
-export function mount(vnode: VNode, fixture: HTMLElement) {
-  vnode.mount(fixture, null);
+export function mount(vnode: VNode, fixture: HTMLElement, afterNode: Node | null = null) {
+  vnode.mount(fixture, afterNode);
 }
 
 export function patch(vnode1: VNode, vnode2: VNode, withBeforeRemove: boolean = false) {

src/component/component_node.ts

@@ -6,6 +6,7 @@ import {
   makeChildFiber,
   makeRootFiber,
   MountFiber,
+  MountOptions,
   RootFiber,
   __internal__destroyed,
 } from "./fibers";
@@ -92,8 +93,8 @@ export class ComponentNode<T extends typeof Component = any> implements VNode<Co
     this.component.setup();
   }
 
-  mountComponent(target: any): Promise<InstanceType<T>> {
-    const fiber = new MountFiber(this, target);
+  mountComponent(target: any, options?: MountOptions): Promise<InstanceType<T>> {
+    const fiber = new MountFiber(this, target, options);
     this.app.scheduler.addFiber(fiber);
     this.initiateRender(fiber);
     return fiber.promise.then(() => this.component);

src/component/fibers.ts

@@ -158,17 +158,30 @@ export class RootFiber extends Fiber {
 
 export let __internal__destroyed: ComponentNode[] = [];
 
+type Position = "first-child" | "last-child";
+
+export interface MountOptions {
+  position?: Position;
+}
+
 export class MountFiber extends RootFiber {
   target: HTMLElement;
+  position: Position;
 
-  constructor(node: ComponentNode, target: HTMLElement) {
+  constructor(node: ComponentNode, target: HTMLElement, options: MountOptions = {}) {
     super(node);
     this.target = target;
+    this.position = options.position || "last-child";
   }
   complete() {
     const node = this.node;
     node.bdom = this.bdom;
-    mount(node.bdom!, this.target);
+    if (this.position === "last-child" || this.target.childNodes.length === 0) {
+      mount(node.bdom!, this.target);
+    } else {
+      const firstChild = this.target.childNodes[0];
+      mount(node.bdom!, this.target, firstChild);
+    }
     node.status = STATUS.MOUNTED;
     this.appliedToDom = true;
     let current;

src/component/props_validation.ts

@@ -6,7 +6,7 @@ import { Component } from "./component";
  * Note that this method does modify in place the props
  */
 export function applyDefaultProps(props: { [key: string]: any }, ComponentClass: typeof Component) {
-  const defaultProps = (ComponentClass as any).defaultProps
+  const defaultProps = (ComponentClass as any).defaultProps;
   if (defaultProps) {
     for (let propName in defaultProps) {
       if (props![propName] === undefined) {
@@ -16,7 +16,6 @@ export function applyDefaultProps(props: { [key: string]: any }, ComponentClass:
   }
 }
 
-
 //------------------------------------------------------------------------------
 // Prop validation helper
 //------------------------------------------------------------------------------