Missing type definitions on ctx.message

[markkarrica]

The message property of ctx has a lot of missing type definitions which don't follow the official ones.

The line of code causing the error was this one:
bot.on("message", (ctx) => ctx.reply(ctx.message.text));
The bot should reply with the text you send to him.

[wojpawlik]

I'm glad you asked! I explained it a few times already, but I think about this a lot, so I have a better understanding each time.

TypeScript is trying to tell you that not every message is a text message.

There are several ways you can proceed in Telegraf 4:

1. Use bot.on('text', (ctx) => ...). It's that simple.
2. Narrow manually: if (!('text' in ctx.message)) return next() (messy when ctx.message might be undefined).
3. Manually use a type guard (not included): if (!has.text(ctx.message)) return next().
4. Pass a type guard to Composer.guard.
5. deunionize(ctx.message).text.

What could Telegraf 5 do?

6. Simply make each Message property always optional. Telegraf 3 did this, and it needs a ton of (unsafe) non-null assertions:

   bot.on('text', ctx => ctx.reply(ctx.message!.text!))
   
   // typechecks, fails at runtime
   bot.on('photo', ctx => ctx.reply(ctx.message!.text!))

7. Add _type discriminator property. One needs to know to check it. Needs extra code that breaks with API updates.
8. deunionize by default. After narrowing manually, suggestions are bloated with multiple ?: undefined properties.

[equt]

You could also use ascription if you're totally sure about the message type, and this brings you zero cost at the runtime.

import { Message } from 'typegram'

// ...

bot.on('text', (ctx) => ctx.reply((ctx.message as Message.TextMessage).text))

// ...

---

I believe this is where TypeScript takes over JavaScript. An explicit type guard is necessary to force you to consider those corner cases.

[wojpawlik]

@equt as is unsafe.

I think I'll Deunionize Context getters in Telegraf 5 (option 8).

[enyineer]

Hi @wojpawlik,
this somehow plays kind of in the same league as the issue itself. Which type for ctx should I use when creating method interfaces for the command handlers? I am using:
bot.on('text', this.someKindOfHandlerFunction);
The type that ctx gets is MatchedContext<Context<Update>, "text"> which by itself is not public and can't be used as a type for the ctx param in "someKindOfHandlerFunction". I am kind of confused, do you have a good idea?
When using Context<Update> as type for ctx the information about the MatchedContext type "text" gets lost.

[wojpawlik]

MatchedContext<Context<Update>, "text"> is equivalent to NarrowedContext<Context, MountMap["text"]>, which is roughly equivalent to Context<MountMap["text"]>.

Context and NarrowedContext are exported, MountMap is not. Should I export it in 4.4? Is there a better name for it?

For now, I suggest copying it.

[enyineer]

I don't have a good idea for a name, but thanks for the clarification. Exporting it for usage in interfaces would be amazing. Thank you very much.

[VeXell]

Hello, can someone explain (or add more details to examples) how to use WizardScene and read user input for specific step. Because a lot of examples uses message.text (for example https://stackoverflow.com/questions/55749437/stage-enter-doesnt-start-the-wizard) but it does not work with typescript. Because if you just started to learn telegraf and without googling this issue #1388 - this is really tricky to understand.

At this moment i found only one simple solution, but i am not sure that is correct.
Thank you.

async (ctx) => {
    await ctx.reply('Step 3');

    if (ctx.message && 'text' in ctx.message) {
        console.log(ctx.message.text);
        return ctx.wizard.next();
    } else {
        return ctx.reply('Please input your details');
    }
},

[bokssssss]

okay thanks the information

[Edward-Fedoruk]

Any updates on this issue?

[atassis]

I got no idea thats going on with my issue, even after seeing a relation between mine and this issue. Thats a plan of maintainers to deal with a lack of typings. I tried to solve that properly somehow in my case, but didnt find any good way by myself
@wojpawlik ?

[MKRhere]

@atassis For your specific case, the correct way to handle it is:

bot.on("message", (ctx, next) => {
	if ("contact" in ctx.message) {
		console.log(ctx.message.contact);
	}
});

TS is (not) telling you that all message updates are not contact messages. When you filter using this if-check, TS knows exactly what kind of message update you're dealing with.

[atassis]

I was using the spreaded variable in the condition and that didn't specify the exact type somehow, "god works in mysterious ways".
And couldn't find the typings in the source code, now I see there is a Typegram being used under the hood, so thats where typings come from

[MKRhere]

Since people are going to find this issue, the new way to filter updates is like so:

import { message } from "telegraf/filters";

bot.use(ctx => {
	if (ctx.has(message("text")) {
		ctx.message.text // works!
	}
});

These filters are also usable in bot.on.

bot.on(message("text"), ctx => {
	ctx.message.text // works!
});

Both bot.on and ctx.has support update type strings (like "message", "edited_message"), but using message types (like "text", "photo") is no longer supported. Filters replace them.

You can also now filter for things you could not before, like editedMessage(), channelPost(), editedChannelPost(), and callbackQuery("data") / callbackQuery("game_short_name"):

import { editedMessage, channelPost } from "telegraf/filters";

bot.on(channelPost("video"), ctx => {
	ctx.channelPost.video // works!
});

This is available since 4.11.0 — I strongly recommend reading the release notes.

We will also keep working on making filters more powerful in v4, and the ctx object even more easier to use in v5.

See also: #1471

[quinn]

would it be possible to show a typed example of:
bot.on('message', (ctx) => {

})

the correct typing of ctx has so far eluded me

[amlxv]

Code from @MKRhere. Sorry for asking a silly question.

bot.on(message("text"), ctx => {
	ctx.message.text // works!
});

If I would like to pass the ctx, what type should I use for handleRequest parameter?

bot.on(message('text'), async (ctx) => {
  await handleRequest(ctx);
});

const handleRequest = async (ctx: ?) => {
    console.log(ctx.message?.text)
};

[MKRhere]

@amlxv

import type { Update, Message } from "telegraf/types";

const handleRequest = async (ctx: Context<Update.MessageUpdate<Message.TextMessage>>) {
	// ...
}

[djeks922]

for custom Context, lets say MyContext where custom session present
when we check for

if(ctx.has(message('text')){
ctx.session
}

Here ts complains about session does not exists.
After ctx.has(...) it converts ctx to use default Context rather that MyContext
Current:
NarrowedContext<Context, Update.MessageUpdate<Record<"text", {}> & Message.TextMessage & AddOptionalKeys>>
Desired:
NarrowedContext<MyContext, Update.MessageUpdate<Record<"text", {}> & Message.TextMessage & AddOptionalKeys>>

[MKRhere]

@djeks922 I cannot reproduce this. Can you show more surrounding code?

[djeks922]

// Define your own context type
export interface MyContext extends Context {
  session?: SessionData;
}

async function usageCheck(
  ctx: MyContext,
  next: () => Promise<void>
)

if (
   ctx.has(message("voice")) &&
   ctx.session?.messagesCount! >= ctx.session?.maxDailyMessages!
 ) {
        return await ctx.sendMessage(freeDailyVoiceLimitResponse);
}

  TS: Property 'session' does not exist on type 'NarrowedContext<Context<Update>, MessageUpdate<Record<"voice", {}> & VoiceMessage & AddOptionalKeys<never>>>'

[djeks922]

export interface SessionData {
  messagesCount: number;
  maxDailyMessages: number;
  currentTopic: string;
  topics: Array<string>;
  maxMonthlyImages: number;
  imagesResetDate: Date;
  imagesCount: number;
  maxDailyVoices: number;
  voiceCount: number ,
  subscription: string;
}

fyi

[djeks922]

I'm not good at typescript so, maybe is there some option to pass MyContext as generic T to .has or similar way?

[djeks922]

'NarrowedContext<Context, MessageUpdate<Record<"voice", {}> & VoiceMessage & AddOptionalKeys>>'
Because has changes MyContext to Context when narrowing, ignoring the parent object type, in our case MyContext

Thanks beforehand, I hope I was able to explain the problem

[MKRhere]

@djeks922 I was able to recreate your problem. Make session non-optional, and make it | undefined:

export interface MyContext extends Context {
- session?: SessionData;
+ session: SessionData | undefined;
}

I cannot explain why this works, but it does. TS is black magic some times.

[atassis]

It means that property session has to be defined, while with question mark operator it doesn't have to

[MKRhere]

@atassis Of course I know that. I wrote the type that narrows down ctx.has. See the thread leading to my reply.