typegram

Types for the Telegram API

This project provides TypeScript types for the entire Telegram API in version 5.0 which was released on November 4, 2020.

It contains zero bytes of executable code.

Installation

npm install --save-dev typegram

Available Types

Generally this package just exposes a huge load of interfaces that correspond to the types used throughout the Telegram API.

Note that the API specification sometimes only has one name for multiple variants of a type, e.g. there is a number of different Updates you can receive, but they're all just called Update. This package represents such types as large unions of all possible options of what an Update could be, such that type narrowing can work as expected on your side. If you need to access the individual variants of an Update, refer to Update.MessageUpdate and its siblings.

In fact, this pattern is used for various types, namely:

• CallbackQuery
• Chat
• ChatFromGetChat
• InlineKeyboardButton
• KeyboardButton
• Message
• MessageEntity
• Update

(Naturally, when the API specification is actually modelling types to be unions (e.g. InlineQueryResult), this is reflected here as a union type, too.)

Available Methods

In addition to the types, this package provides you with another type Telegram which contains all available methods of the API. There is no further structure applied to this, but if you can come up with something reasonable, please suggest it in an issue or directly open a PR.

Each method takes just a single argument with a structure that corresponds to the object expected by Telegram. If you need to directly access that type, consider using Opts<M> where M is the method name (e.g. Opts<'getMe'>).

Note that Opts<M> will give you an empty object type (i.e. {}) for methods that do not take any parameters. That is to say, it will not give you a type error or undefined (as opposed to something like Parameters<Telegram['getMe']>[0]).

Caveat with JSON-Serialized Objects

Some methods of the Telegram API are expected to be called with JSON-serialized objects contained in a property of the payload, rather than an actual JSON payload. In other words, the objects are serialized twice—the first time in order to conform with the docs, and the second time when the payload is actually sent in the POST body to the API server.

The most prominent example is the reply_markup property that appears in a number of different methods, but more than a dozen other properties like this can be found throughout the API.

Strictly speaking, the typegram types do not reflect this accurately. Instead of using string (representing a serialized object) as the type, typegram uses the type of the object itself, thus ignoring the serialization step. For instance, instead of declaring reply_markup: string, it declares the property as reply_markup: InlineKeyboardMarkup | ReplyKeyboardMarkup | ReplyKeyboardRemove | ForceReply because that is what is supposed to be serialized to string before calling the respective method.

This makes sense for two reasons.

1. The goal of this library is to provide type safety. However, the contents of a string cannot be typechecked for being valid JSON of the correct object. As a result, we would be missing type safety if we would only model the properties as string.
2. A common use case for this library is to pull the types into some wrapper code around the Telegram Bot API. This wrapper code often does the necessary JSON serialization automatically for the required properties. The consumer then does not need to care about which properties to serialize and which not. Given that typegram refers to the objects themselves instead of their serialized strings, the wrapper code can now simply expose the typegram types to its consumers without having to transform them before.

Using Promises

All of the methods are specified with the actual return type of the Telegram API. If you need them to return Promises instead, consider using TelegramP. This type maps all methods of Telegram to a promisified version.

Customizing InputFile

The Telegram API lets bots send files in three different ways. Two of those ways are by specifying a string—either a file_id or a URL. The third option, however, is by uploading files to the server.

Depending on the code you're using the typegram types for, you may want to support different ways to specify the file to be uploaded. As an example, you may want to be able to make calls to sendDocument with an object that conforms to { path: string } in order to specify the location of a local file. (Your code is then assumed to able to handle calls to sendDocument and the like when supplied with an object alike { path: '/tmp/file.txt' } for the document property of the argument object.)

typegram cannot possibly know what objects you want to support as InputFiles. Consequently, the exposed type InputFile is merely an alias for string, thus covering the first two means to send a file.

However, you can specify your own version of what an InputFile is, hence effectively creating a completely new version of typegram with your custom InputFile type used throughout all affected methods and interfaces.

For instance, let's stick with our example and say that you want to support InputFiles of the following type.

interface MyInputFile {
  path: string;
}

You can then customize typegram to fit your needs by

1. importing the magical Typegram proxy type and
2. setting this alias:

type MyTypegram = Typegram<MyInputFile>;

You can now access all types that must respect MyInputFile through the MyTypegram type:

// The `Telegram` type that contains all API methods:
type Telegram = MyTypegram["Telegram"];
// or, respectively
type TelegramP = MyTypegram["TelegramP"];

// The utility type `Opts`:
type Opts<M extends keyof Telegram> = MyTypegram["Opts"][M];

// The adjusted `InputMedia*` types:
type InputMedia = MyTypegram["InputMedia"];
type InputMediaPhoto = MyTypegram["InputMediaPhoto"];
type InputMediaVideo = MyTypegram["InputMediaVideo"];
type InputMediaAnimation = MyTypegram["InputMediaAnimation"];
type InputMediaAudio = MyTypegram["InputMediaAudio"];
type InputMediaDocument = MyTypegram["InputMediaDocument"];

All other interfaces are unaffected by the customization through MyInputFile. They can simply continued to be imported directly from typegram.

Where Do the Types Come from

They're handwritten.

That is, they're of course not entirely handwritten. The initial version of them were produced in one afternoon by a combination of copying and pasting from the website, VIM magic, regular expressions and VSCode auto-formatting the rest.

After that, some more work and a few community contributions did the polishing.

Future updates to the API will be integrated manually in a similar fashion.

Other people's previous attempts to harvest the types directly from the website using a script failed due to the required effort of handling special cases about the layout of the website.