Suggestion for on-responded on prompts

On issue microsoft#3947, relying on the responded flag todecide whether to show the prompt interferes with logic that could be happening either

a. Concurrently
b. On some middleware
c. As part of how we reached the prompt

I believe the *intention* is to prevent sending a prompt twice to the user, using a symbol may be enough for that, without relying on global status

libraries/botbuilder-dialogs/src/prompts/prompt.ts

@@ -172,6 +172,29 @@ export abstract class Prompt<T> extends Dialog {
      */
     protected constructor(dialogId: string, private validator?: PromptValidator<T>) {
         super(dialogId);
+
+        if (validator){
+            this.validator = async (prompt) => {
+
+                const hasRespondedBeforeValidator = prompt.context.responded;
+                // Making the validator *only* consider as "responded" if responded has been set during a turn
+                // @ts-expect-error 
+                prompt.context._respondedRef.responded = false;
+                try {
+                    const result = await validator(prompt);
+                    if (prompt.context.responded) {
+                        if (prompt.context.turnState.get(Prompt.shouldReprompt) == null){
+                            Prompt.setRepromptStatus(prompt.context, false);
+                        }
+                    }
+                    return result;
+                } finally {
+                    if (hasRespondedBeforeValidator) prompt.context.responded = true;
+                }
+            }
+        }
+
+
     }
 
     /**
@@ -206,6 +229,31 @@ export abstract class Prompt<T> extends Dialog {
         return Dialog.EndOfTurn;
     }
 
+    /**
+     * By default the bot re-prompts if there has not been any message sent to this user in this turn
+     * 
+     * However, that might be undesirable, you can set here whether you want it to reprompt or not.
+     * 
+     * To reset to the default status, you can set it back to undefined or null.
+     * @param context 
+     * @param shouldReprompt 
+     */
+    static setRepromptStatus(context:TurnContext, shouldReprompt: boolean | undefined | null = true) {
+        context.turnState.set(this.shouldReprompt, shouldReprompt);
+    }
+
+    protected shouldReprompt(context: TurnContext): boolean {
+        const shouldReprompt = context.turnState.get(Prompt.shouldReprompt);
+        if (shouldReprompt == null) return !context.responded;
+        return shouldReprompt;
+    }
+
+
+    /**
+     * Optional symbol to be used to *force* the context whether to reprompt or not based on the flag
+     */
+    private static shouldReprompt = Symbol('shouldReprompt');
+
     /**
      * Called when a prompt dialog is the active dialog and the user replied with a new activity.
      * @param dc The [DialogContext](xref:botbuilder-dialogs.DialogContext) for the current turn of conversation.
@@ -238,6 +286,7 @@ export abstract class Prompt<T> extends Dialog {
 
         // Validate the return value
         let isValid = false;
+
         if (this.validator) {
             if (state.state['attemptCount'] === undefined) {
                 state.state['attemptCount'] = 0;
@@ -257,9 +306,9 @@ export abstract class Prompt<T> extends Dialog {
         if (isValid) {
             return await dc.endDialog(recognized.value);
         } else {
-            if (!dc.context.responded) {
+            if (this.shouldReprompt(dc.context)) {
                 await this.onPrompt(dc.context, state.state, state.options, true);
-            }
+            } 
 
             return Dialog.EndOfTurn;
         }