Mattermost API Client in Dart

This is an implementation of a Mattermost API client in dart. It is not the only one, but it has significant advantages over others.

The other package called mattermost_dart depends on the dio library and therefore also on a number of others, but I think libraries should have the minimal number of dependencies possible, so this implementation depends only on the http library.

Additionally, there are incompatibilities between the openapi-generator-cli and the published mattermost swagger document. I have resolved many of those issues. See below.


This library is a full implementation of the Mattermost Client API 4.0.0 in Dart.

Getting started

Install the package

dart pub add mattermost_api

Import the package in your Dart file

import 'package:mattermost_api/api.dart';

Creating a client

var mmClient = MattermostApiClient(
  basePath: '$mmBaseUrl/api/v4',
  authentication: MmHttpBearerAuthentication(config.mmToken),

Available authentication classes:

  • MmApiKeyAuthentication
  • MmHttpBasicAuthentication
  • MmHttpBearerAuthentication
  • MmOAuth

Accessing the API endpoints

There are many sub-apis available on Mattermost and they are exposed by getters on the MattermostApiClient object or may be created on their own.

Make your requests:

// using getters on the client instance
MmTeam? team = await mmClient.teams.getTeamByName(myTeamName);
MmChannel? channel = await mmClient.channels.getChannel(myChannelId);

// using the classes directly
var channelApi = MattermostChannelsApi(mmClient)
MmChannel? channel = await channelApi.getChannel(myChannelId);

Every API model in the library is prefixed with the word Mattermost and every object class is prefixed with the letters Mm so if you are using an IDE, simply start typing either Mattermost or Mm and your IDE should pick up everything that's available.

Using the Websocket Client for Real-time Updates

The library also exposes a simple wrapper around the Mattermost Websocket API for retrieving real-time updates. This is essential for bot accounts that need to reply to channel messages or direct messages.

Here's an example.

var token = 'BEARER_TOKEN';
var url = 'wss://BASE_URL/api/v4/websocket';
var ws = MattermostWebsocketClient(
  headers: {'Authorization': 'Bearer $token'},
  onEvent: (MmWsEvent mm) {
    if (mm is MmWsEventPosted) print('a user just posted a message!');

await Future.delayed(Duration(seconds: 2));
var res = await ws.userTyping('CHANNEL_ID_WHERE_USER_IS_TYPING');
Future.delayed(Duration(seconds: 2));
res = await ws.getStatuses();
await Future.delayed(Duration(seconds: 2));
res = await ws.getStatusesByIds(['USER_ID_TO_GET']);

Note: the websocket API is significantly different from the REST API, and this library is still limited in its support. All events are supported through the MmWsEvent wrapper class, and as this library improves, we will add wrapper classes for the other events too.

Mattermost Websocket Documentation

More Details

Issues Resolved

mattermost swagger json schema errors

The mattermost swagger json document available here: has some OpenAPI schema errors in it. I have fixed them and my version is located here in this repo as mattermost-swagger.json.

Additionally, the swagger document inconsistently capitalizes ldap in tags (endpoints). The code generator sees them as different apis, but we only want one, so I have modified the swagger document to make them all LDAP instead.

dart codegen problems

Additionally, when using the official openapi-generator-cli (version 6.0), the automatic Dart code generation has a few problems:

  • The underscore query variable allowed when retrieving a user's profile image resolves to a space character in the resulting Dart code and breaks compilation.
  • The generated code sometimes attempts to return objects of the wrong type.
  • The generated code fails to properly recognize empty OpenAPI object types as a Map<dynamic> and treats them as Object instead.
  • The generated code expects that we want the entire library to be automatically generated, and it creates a pubspec.yaml and everything. Since there are problems with the automatic code generation, it's better and safer to wrap the auto-generated code in a library we control.

I have resolved these problems by forking the openapi-generator-cli here to change the Dart code generator Java class and templates. Also, I have created my own build script ( that does the following:

  • processes the swagger json using my custom build of openapi-generator-cli and my new templates (also in this repo under openapi_mattermost_templates).
  • makes a few additional replacements in the generated code
  • ignores the generated pubspec and instead copies the generated lib, test, and doc files into their final resting place.


This file exposes the websocket interface to Mattermost. Since it is not defined in the openAPI spec, we have to implement it manually here.