Bot framework javascript_nodejs v4: Unable to use Default Locale in DateTimePrompt (Dutch)

In a waterfall dialog step, I need a date from the user. The users language is Dutch. I have tried multiple options, but the locale keeps using 'en-en'. Dutch dates like '1 April' and '26 Juni' are not recognized.

My prompt:

this.addDialog(new DateTimePrompt(WHEN_PROMPT, this.datePromptValidator, 'nl-nl'));

I use it like this

const promptOptions = { retryPrompt: 'Hier kan ik geen datum uithalen.' };
return await stepContext.prompt(WHEN_PROMPT, promptOptions);

and the validator

async datePromptValidator(promptContext) {
    return promptContext.recognized.succeeded;
}

Would appreciate some help...

Solution

This of "defaultLocale" as more of a fall-back if there's no indication what the user's locale is supposed to be.

In the current code, activity.locale is used first, if it exists:

const locale: string =  activity.locale || this.defaultLocale || 'en-us';

This is what's specified in the param info:

@param defaultLocale (Optional) locale to use if TurnContext.activity.locale is not specified. Defaults to a value of en-us.

This is the same for other prompts:

If you're running into this when testing, here's how to change locale in a few clients:

Emulator:

WebChat:

window.WebChat.renderWebChat(
        {
          directLine: window.WebChat.createDirectLine({
            token: 'YOUR_DIRECT_LINE_TOKEN'
          }),
          userID: 'YOUR_USER_ID',
          username: 'Web Chat User',
          locale: 'en-US', // CHANGE THIS HERE!!
          botAvatarInitials: 'WC',
          userAvatarInitials: 'WW'
        },
        document.getElementById('webchat')
      );

Teams:

Click your profile, then Settings, then: