feat(InputBinding): subscribe callback now supports event priority

NEWS.md

@@ -8,6 +8,8 @@
 
 * The family of `update*Input()` functions can now render HTML content passed to the `label` argument (e.g., `updateInputText(label = tags$b("New label"))`). (#3996)
 
+* The `callback` argument of Shiny.js' `InputBinding.subscribe()` method gains support for a value of `"event"`. This makes it possible for an input binding to use event priority when updating the value (i.e., send immediately and always resend, even if the value hasn't changed). (#4211)
+
 ## Changes
 
 * Shiny no longer suspends input changes when _any_ `<input type="submit">` or `<button type="submit">` is on the page. Instead, it now only suspends when a `submitButton()` is present. If you have reason for creating a submit button from custom HTML, add a CSS class of `shiny-submit-button` to the button. (#4209)

srcts/src/bindings/input/inputBinding.ts

@@ -1,6 +1,20 @@
+import type { EventPriority } from "../../inputPolicies/inputPolicy";
 import type { RatePolicyModes } from "../../inputPolicies/inputRateDecorator";
 import type { BindScope } from "../../shiny/bind";
 
+type SubscribeEventPriority =
+  | EventPriority
+  | boolean
+  | { priority: EventPriority };
+// Historically, the .subscribe()'s callback value only took a boolean. In this
+// case:
+//   * false: send value immediately (i.e., priority = "immediate")
+//   * true: send value later (i.e., priority = "deferred")
+//     * The input rate policy is also consulted on whether to debounce or
+//       throttle
+// In recent versions, the value can also be "event", meaning that the
+// value should be sent immediately regardless of whether it has changed.
+
 class InputBinding {
   name!: string;
 
@@ -26,10 +40,10 @@ class InputBinding {
     el; // unused var
   }
 
-  // The callback method takes one argument, whose value is boolean. If true,
-  // allow deferred (debounce or throttle) sending depending on the value of
-  // getRatePolicy. If false, send value immediately. Default behavior is `false`
-  subscribe(el: HTMLElement, callback: (value: boolean) => void): void {
+  subscribe(
+    el: HTMLElement,
+    callback: (value: SubscribeEventPriority) => void
+  ): void {
     // empty
     el; // unused var
     callback; // unused var
@@ -102,3 +116,4 @@ class InputBinding {
 //// END NOTES FOR FUTURE DEV
 
 export { InputBinding };
+export type { SubscribeEventPriority };

srcts/src/shiny/bind.ts

@@ -1,13 +1,15 @@
 import $ from "jquery";
 import { Shiny } from "..";
 import type { InputBinding, OutputBinding } from "../bindings";
+import type { SubscribeEventPriority } from "../bindings/input/inputBinding";
 import { OutputBindingAdapter } from "../bindings/outputAdapter";
 import type { BindingRegistry } from "../bindings/registry";
 import { ShinyClientMessageEvent } from "../components/errorConsole";
 import type {
   InputRateDecorator,
   InputValidateDecorator,
 } from "../inputPolicies";
+import type { EventPriority } from "../inputPolicies/inputPolicy";
 import { shinyAppBindOutput, shinyAppUnbindOutput } from "./initedMethods";
 import { sendImageSizeFns } from "./sendImageSize";
 
@@ -27,7 +29,7 @@ function valueChangeCallback(
   inputs: InputValidateDecorator,
   binding: InputBinding,
   el: HTMLElement,
-  allowDeferred: boolean
+  priority: EventPriority
 ) {
   let id = binding.getId(el);
 
@@ -37,17 +39,7 @@ function valueChangeCallback(
 
     if (type) id = id + ":" + type;
 
-    const opts: {
-      priority: "deferred" | "immediate";
-      binding: typeof binding;
-      el: typeof el;
-    } = {
-      priority: allowDeferred ? "deferred" : "immediate",
-      binding: binding,
-      el: el,
-    };
-
-    inputs.setInput(id, value, opts);
+    inputs.setInput(id, value, { priority, binding, el });
   }
 }
 
@@ -272,8 +264,20 @@ function bindInputs(
         const thisBinding = binding;
         const thisEl = el;
 
-        return function (allowDeferred: boolean) {
-          valueChangeCallback(inputs, thisBinding, thisEl, allowDeferred);
+        return function (priority: SubscribeEventPriority) {
+          // Narrow the type of priority to EventPriority
+          let normalizedPriority: EventPriority;
+          if (priority === true) {
+            normalizedPriority = "deferred";
+          } else if (priority === false) {
+            normalizedPriority = "immediate";
+          } else if (typeof priority === "object" && "priority" in priority) {
+            normalizedPriority = priority.priority;
+          } else {
+            normalizedPriority = priority;
+          }
+
+          valueChangeCallback(inputs, thisBinding, thisEl, normalizedPriority);
         };
       })();
 

srcts/types/src/bindings/input/inputBinding.d.ts

@@ -1,12 +1,16 @@
+import type { EventPriority } from "../../inputPolicies/inputPolicy";
 import type { RatePolicyModes } from "../../inputPolicies/inputRateDecorator";
 import type { BindScope } from "../../shiny/bind";
+type SubscribeEventPriority = EventPriority | boolean | {
+    priority: EventPriority;
+};
 declare class InputBinding {
     name: string;
     find(scope: BindScope): JQuery<HTMLElement>;
     getId(el: HTMLElement): string;
     getType(el: HTMLElement): string | null;
     getValue(el: HTMLElement): any;
-    subscribe(el: HTMLElement, callback: (value: boolean) => void): void;
+    subscribe(el: HTMLElement, callback: (value: SubscribeEventPriority) => void): void;
     unsubscribe(el: HTMLElement): void;
     receiveMessage(el: HTMLElement, data: unknown): Promise<void> | void;
     getState(el: HTMLElement): unknown;
@@ -18,3 +22,4 @@ declare class InputBinding {
     dispose(el: HTMLElement): void;
 }
 export { InputBinding };
+export type { SubscribeEventPriority };