Add comment; removing logging

NEWS.md

@@ -12,6 +12,8 @@
 
 * `Map` objects are now initialized at load time instead of build time. This avoids potential problems that could arise from storing `fastmap` objects into the built Shiny package. (#3775)
 
+* Closed #3635: `window.Shiny.outputBindings` and `window.Shiny.inputBindings` gain a `onRegister()` method, to register callbacks that execute whenever a new binding is registered. Internally, Shiny uses this to check whether it should re-bind to the DOM when a binding has been registered. (#3638)
+
 ### Bug fixes
 
 * Fixed #3771: Sometimes the error `ion.rangeSlider.min.js: i.stopPropagation is not a function` would appear in the JavaScript console. (#3772)

srcts/src/bindings/registry.ts

@@ -1,4 +1,5 @@
 import { mergeSort } from "../utils";
+import { Callbacks } from "../utils/callbacks";
 
 interface BindingBase {
   name: string;
@@ -14,6 +15,7 @@ class BindingRegistry<Binding extends BindingBase> {
   name!: string;
   bindings: Array<BindingObj<Binding>> = [];
   bindingNames: { [key: string]: BindingObj<Binding> } = {};
+  registerCallbacks: Callbacks = new Callbacks();
 
   register(binding: Binding, bindingName: string, priority = 0): void {
     const bindingObj = { binding, priority };
@@ -23,6 +25,12 @@ class BindingRegistry<Binding extends BindingBase> {
       this.bindingNames[bindingName] = bindingObj;
       binding.name = bindingName;
     }
+
+    this.registerCallbacks.invoke();
+  }
+
+  onRegister(fn: () => void, once = true): void {
+    this.registerCallbacks.register(fn, once);
   }
 
   setPriority(bindingName: string, priority: number): void {

srcts/src/shiny/init.ts

@@ -150,6 +150,24 @@ function initShiny(windowShiny: Shiny): void {
     (x) => x.value
   );
 
+  // When future bindings are registered, rebind to the DOM once the current
+  // event loop is done. This is necessary since the binding might be registered
+  // after Shiny has already bound to the DOM (#3635)
+  let enqueuedCount = 0;
+  const enqueueRebind = () => {
+    enqueuedCount++;
+    windowShiny.shinyapp?.actionQueue.enqueue(() => {
+      enqueuedCount--;
+      // If this function is scheduled more than once in the queue, don't do anything.
+      // Only do the bindAll when we get to the last instance of this function in the queue.
+      if (enqueuedCount === 0) {
+        windowShiny.bindAll?.(document.documentElement);
+      }
+    });
+  };
+  inputBindings.onRegister(enqueueRebind, false);
+  outputBindings.onRegister(enqueueRebind, false);
+
   // The server needs to know the size of each image and plot output element,
   // in case it is auto-sizing
   $(".shiny-image-output, .shiny-plot-output, .shiny-report-size").each(

srcts/src/utils/callbacks.ts

@@ -0,0 +1,45 @@
+type Cb = {
+  once: boolean;
+  fn: () => void;
+};
+
+type Cbs = {
+  [key: string]: Cb;
+};
+
+class Callbacks {
+  callbacks: Cbs = {};
+  id = 0;
+
+  register(fn: () => void, once = true): () => void {
+    this.id += 1;
+    const id = this.id;
+
+    this.callbacks[id] = { fn, once };
+    return () => {
+      delete this.callbacks[id];
+    };
+  }
+
+  invoke(): void {
+    for (const id in this.callbacks) {
+      const cb = this.callbacks[id];
+
+      try {
+        cb.fn();
+      } finally {
+        if (cb.once) delete this.callbacks[id];
+      }
+    }
+  }
+
+  clear(): void {
+    this.callbacks = {};
+  }
+
+  count(): number {
+    return Object.keys(this.callbacks).length;
+  }
+}
+
+export { Callbacks };

srcts/types/src/bindings/registry.d.ts

@@ -1,3 +1,4 @@
+import { Callbacks } from "../utils/callbacks";
 interface BindingBase {
     name: string;
 }
@@ -12,7 +13,9 @@ declare class BindingRegistry<Binding extends BindingBase> {
     bindingNames: {
         [key: string]: BindingObj<Binding>;
     };
+    registerCallbacks: Callbacks;
     register(binding: Binding, bindingName: string, priority?: number): void;
+    onRegister(fn: () => void, once?: boolean): void;
     setPriority(bindingName: string, priority: number): void;
     getPriority(bindingName: string): number | false;
     getBindings(): Array<BindingObj<Binding>>;

srcts/types/src/utils/callbacks.d.ts

@@ -0,0 +1,16 @@
+type Cb = {
+    once: boolean;
+    fn: () => void;
+};
+type Cbs = {
+    [key: string]: Cb;
+};
+declare class Callbacks {
+    callbacks: Cbs;
+    id: number;
+    register(fn: () => void, once?: boolean): () => void;
+    invoke(): void;
+    clear(): void;
+    count(): number;
+}
+export { Callbacks };