[FIX] Renderer: fix rendering promises

The render function (of the renderer) can be called many times
synchronously, the render functions are called for all nodes even if they
are rendered together. Example, in a for loop, we call render (of the
renderer) for a text, so the render function is called for each
character. It is necessary to check in the promise (including in the
following microtask) if the rendering has not already been done.

packages/plugin-renderer/src/RenderingEngine.ts

@@ -90,10 +90,20 @@ export class RenderingEngine<T = {}> {
      * @param nodes
      * @param rendering
      */
-    async rendered(nodes: VNode[], rendering: [Renderer<T>, Promise<T>]): Promise<T> {
+    async rendered(nodes: VNode[], renderer: Renderer<T>, rendered: Promise<T>): Promise<T> {
         for (const node of nodes) {
-            const renderings = this.renderings.get(node) || [];
-            renderings.push(rendering);
+            let renderings = this.renderings.get(node);
+            if (!renderings) {
+                renderings = [];
+                this.renderings.set(node, renderings);
+            }
+            const index = renderings.findIndex(rendering => rendering[0] === renderer);
+            if (index === -1) {
+                renderings.push([renderer, rendered, true]);
+            } else {
+                renderings[index][1] = rendered;
+                renderings[index][2] = true;
+            }
         }
         return rendered;
     }
@@ -137,10 +147,15 @@ export class RenderingEngine<T = {}> {
         // later with the same return value as the asynchronous render call.
         const rendererProm = new Promise<T>((resolve): void => {
             Promise.resolve().then(() => {
-                nextRenderer.render(node).then(resolve);
+                const rendering = renderings.find(rendering => rendering[0] === nextRenderer);
+                const promise = rendering[2] ? rendering[1] : nextRenderer.render(node);
+                promise.then((n: T) => {
+                    rendering[2] = true;
+                    resolve(n);
+                });
             });
         });
-        renderings.push([nextRenderer, rendererProm]);
+        renderings.push([nextRenderer, rendererProm, false]);
         this.renderings.set(node, renderings);
         return rendererProm;
     }