onError (Error Handling)

Errors can occur in middleware, and we need to handle them. That's exactly what the onError hook is designed for.

bot.on("message", () => {
    bot.api.sendMessage({
        chat_id: "@not_found",
        text: "Chat not exists....",
    });
});

bot.onError(({ context, kind, error }) => {
    if (context.is("message")) return context.send(`${kind}: ${error.message}`);
});

Add hook only to specified contexts

bot.onError("message", ({ context, kind, error }) => {
    return context.send(`${kind}: ${error.message}`);
});
// or array
bot.onError(["message", "message_reaction"], ({ context, kind, error }) => {
    return context.send(`${kind}: ${error.message}`);
});

Error kinds

Custom

You can catch an error of a certain class inherited from Error.

export class NoRights extends Error {
    needRole: "admin" | "moderator";

    constructor(role: "admin" | "moderator") {
        super();
        this.needRole = role;
    }
}

const bot = new Bot(process.env.BOT_TOKEN as string)
    .error("NO_RIGHTS", NoRights)
    .onError("message", ({ context, kind, error }) => {
        if (kind === "NO_RIGHTS")
            return context.send(
                format`You don't have enough rights! You need to have a «${bold(
                    error.needRole
                )}» role.`
            );
    });

bot.on("message", (context) => {
    if (context.text === "ban") throw new NoRights("admin");
});

IMPORTANT

We recommend following the convention of naming error kinds in SCREAMING_SNAKE_CASE

Telegram

This error is the result of a failed request to the Telegram Bot API.

bot.onError(({ context, kind, error }) => {
    if (kind === "TELEGRAM" && error.method === "sendMessage") {
        error.params; // is sendMessage params
    }
});

Unknown

This error is any unknown error, whether it's your custom class or just a standard Error.

bot.onError(({ context, kind, error }) => {
    if (kind === "UNKNOWN") {
        console.log(error.message);
    }
});