Discourseプラグインの開発 - 第1部 - 基本的なプラグインの作成

[Discourse]

Discourseでプラグインを作成するのは、いくつかの癖を理解すればとても簡単です。この投稿の目的は、プラグインの骨組みを作成し、基本的な部分を紹介します。

開発環境

Discourseの開発環境があなたのコンピュータで実行されていることを確認してください。適切なセットアップガイド を使用することをお勧めし、完了後に戻ってきてください。

plugin.rb

GitHub - discourse/discourse-plugin-skeleton: Template for Discourse plugins · GitHub を使用して、pluginsディレクトリに完全なDiscourseプラグインの骨組みを作成できます

現在、この骨組みはDiscourseのコアにバンドルされており、rake plugin:create[plugin-name] を実行すると、この骨組みを使用してプラグインが作成されます

Discourseが起動すると、plugins ディレクトリ内の plugin.rb ファイルを含むサブディレクトリを探します。plugin.rb ファイルには2つの目的があります。1つ目は、プラグインのマニフェストとして、プラグインに関する必須情報（名前、連絡先情報、説明）を含むことです。2つ目の目的は、プラグインの実行に必要なRubyコードを初期化することです。

今回の場合、Rubyコードは追加しませんが、それでも plugin.rb が必要です。basic-plugin というディレクトリを作成し、その中に以下の内容を含む plugin.rb ファイルを作成しましょう。

basic-plugin/plugin.rb

# name: basic-plugin
# about: A super simple plugin to demonstrate how plugins work
# version: 0.0.1
# authors: Awesome Plugin Developer
# url: https://github.com/yourusername/basic-plugin

このファイルを作成したら、ローカルサーバーを再起動し、プラグインが読み込まれるはずです。

重要な注意点！

通常のRails開発に慣れている方なら、プラグインはリロードに関してそれほど快適ではないことに気づくかもしれません。一般的に、プラグインに変更を加えた場合は、Ctrl+c を押してサーバーを停止し、その後 bin/dev を使用して再度実行する必要があります。

変更が反映されませんでした！

新しいファイルを作成したり、古いファイルを削除したりした場合、キャッシュが完全にクリアされないことがあります。この問題を回避するには、tmp フォルダを削除し、Railsを再起動してください。Macでは、1つのコマンドで実行できます：rm -rf tmp; bin/dev。

プラグインが読み込まれたことを確認する

ローカルサーバーを再起動した後、/admin/plugins のURLにアクセスしてください（プラグインレジストリは管理者のみが見られるため、まず管理者アカウントとしてログイン していることを確認してください）。

すべて正常に動作している場合、リストにプラグインが表示されるはずです：

おめでとうございます、最初のプラグインを作成しました！

JavaScriptを追加してみましょう

現在、あなたのプラグインは何もしていません。Discourseが読み込まれたときにアラートボックスを表示するJavaScriptファイルを追加しましょう。これはユーザーにとって非常に面倒ですが、実際のプラグインとしては推奨されませんが、実行中のアプリケーションにJavaScriptを挿入する方法を示します。

以下のファイルを作成してください：

plugins/basic-plugin/assets/javascripts/discourse/initializers/alert.js

export default {
  name: "alert",
  initialize() {
    alert("alert boxes are annoying!");
  },
};

これでローカルサーバーを再起動すると、画面に “alert boxes are annoying!” が表示されるはずです。（表示されなかった場合は、上記の「変更が反映されませんでした！」のセクションを参照してください）。

この仕組みを段階的に見ていきましょう：

1. assets/javascripts/discourse/initializers に配置されたJavaScriptファイルは、Discourseアプリケーションが読み込まれたときに自動的に実行されます。

2. この特定のファイルは、name と initialize 関数を持つ1つのオブジェクトを export しています。

3. name は一意である必要があるため、ここでは alert と命名しました。

4. initialize() 関数は、アプリケーションが読み込まれたときに呼び出されます。今回の場合、単に alert() コードを実行するだけです。

これで、公式のDiscourseプラグイン開発者です！

---

シリーズの続き

Part 1: このトピック
Part 2: Plugin Outlets
Part 3: Site Settings
Part 4: git setup
Part 5: Admin interfaces
Part 6: Acceptance tests
Part 7: Publish your plugin

---

このドキュメントはバージョン管理されています - 変更を提案するには GitHub をご利用ください。

[Ishan_Dutta]

I am able to create plugin in development, it works fine. Thanks.
But I don’t see a way to install other’s plugin in development
So first question is how can I fork someone’s plugin in development and then build on top of that(hope copy paste that repo is not the recommended way)?
Second question is, it seems my created plugin is part of my repo, is there a way to create a separate github repo for the plugin automatically which others can directly use to install?

[eviltrout (Robin Ward)]

I have a preferred method to do this. First, I have a ~/code directory where I have all my git projects. So I check out discourse and the plugin in that directory so it’s something like this:

~/code

discourse
discourse-some-plugin

Then, within the ~/code/discourse/plugins folder I create a symlink to the plugin:

$ cd ~/code/discourse/plugins
$ ln -s ~/code/discourse-some-plugin .

Then for good measure:

$ cd ~/code/discourse
$ rm -rf tmp
$ bundle exec rails server

Now you can fork the plugin in ~/code/discourse-some-plugin, make pull requests or whatever you want. It’ll be used by discourse.

[Jithin_Krishnan]

What is the best way to render ajax response inside a widget?
I was able to console.log the ajax response, but it is not rendering inside the widget.

Tried to call this.scheduleRerender() after getting ajax response but both results in an infinite loop.

[Jithin_Krishnan]

I am getting following error when trying to load a helper module inside my widget

Could you please help me to resolve this error?
Thanks

[eviltrout (Robin Ward)]

@Jithin_Krishnan

What is the best way to render ajax response inside a widget?

You should make sure your widget can contain state. After the ajax request, set it on the state object and trigger a this.scheduleRerender and it should appear. For an example look at how the post menu shows who liked something.

@Jithin_Krishnan

I am getting following error when trying to load a helper module inside my widget

Looks like you have the wrong path to your helper. One way to see all the paths that Discourse has resolved is by typing require._eak_seen in your console. Look for the correct path name.

[Jithin_Krishnan]

Thanks Robin Ward for your help. I was able to load my module after investigating with require._eak_seen.

Below is the code for my widget. The problem is that this.scheduleRerender() is causing an infinite loop. The div always shows loading animation (even without this.scheduleRerender) which seems this.state.loading is not being set.

import { createWidget } from 'discourse/widgets/widget';
import { getTopic } from 'discourse/plugins/my-plugin/discourse/helpers/topics';
import { ajax } from 'discourse/lib/ajax';
import { h } from 'virtual-dom';

export default createWidget('topic-widget', {
  tagName: 'div.my-topics',
  defaultState() {
    return { loading: false};
  },

  refreshTopic() {
    if (this.state.loading) { return; }
    this.state.loading = true;
    this.state.topic = 'empty';
    getTopic(this).then((result) => {
      console.log(result);
      this.state.topic = result;
      this.state.loading = false;
      this.scheduleRerender();
    });
  },

  html(attrs, state) {
    if (!state.topic) {
      this.refreshTopic();
    }
    const result = [];
    if (state.loading) {
      result.push(h('div.spinner-container', h('div.spinner')));
    } else if (state.topic !== 'empty') {
      result.push(state.topic);
    } else {
      result.push(h('div.no-messages', 'No topic.'))
    }

    return result;
  },
});

Could you help to resolve this error?

[eviltrout (Robin Ward)]

Your code looks mostly fine, however, all widgets that deal with state require a key attribute. You should have seen a warning about this, although maybe the warning only appears when running tests?

Try adding a buildKey function like buildKey: () => 'topic-widget'.

That should probably fix it. Also, a much less serious issue is you might want to add topic: null to your state object. Javascript is much faster when it knows the shape of the object in advance.

[Jithin_Krishnan]

Thanks Robin Ward.
Adding buildKey function worked fine for me.

[tgxworld (Alan Tan)]

@Jithin_Krishnan

The problem is that this.scheduleRerender() is causing an infinite loop.

@eviltrout

Your code looks mostly fine, however, all widgets that deal with state require a key attribute. You should have seen a warning about this, although maybe the warning only appears when running tests?

@eviltrout I got bitten by this in development and didn’t get a warning about setting a key attribute.

[eviltrout (Robin Ward)]

Ah, it only warns in Ember.testing:

https://github.com/discourse/discourse/blob/master/app/assets/javascripts/discourse/widgets/widget.js.es6#L153

We might want to just raise an error if that happens now? It is pretty dangerous for Widgets to do that.

[tgxworld (Alan Tan)]

for raising an error instead. Maybe we can extend that to development too?

[eviltrout (Robin Ward)]

Hopefully this will prevent others from making this mistake:

https://github.com/discourse/discourse/commit/d4bbdcd7d63ddbf20239c95d1ba1cee9030d7e95

[Sudaraka (Sudaraka Jayathilaka)]

Hi,

@eviltrout

but will show how to insert Javascript into our running application.

Create the following file:

plugins/basic-plugin/assets/javascripts/discourse/initializers/alert.js.es6

Is this url correct? Shouldn’t this be ,

plugins/basic-plugin/assets/javascripts/initializers/alert.js.es6

I’m new here. please correct me if im wrong

[vinothkannans (Vinoth Kannan)]

In Discourse, mainly there are two big JavaScript sections “discourse” and “admin”. Also you can see few more in https://github.com/discourse/discourse/tree/master/app/assets/javascripts.

In plugins, to differentiate admin & normal user section JavaScript files we use “discourse” and “admin” keywords in between like below

plugins/basic-plugin/assets/javascripts/discourse/initializers/alert.js.es6
plugins/basic-plugin/assets/javascripts/admin/initializers/alert.js.es6

---

@Sudaraka

plugins/basic-plugin/assets/javascripts/initializers/alert.js.es6

Also it will just work even without identification keywords like you mentioned

[Sudaraka (Sudaraka Jayathilaka)]

@vinothkannans Thank you a lot for the explanation.

[pacharanero (Marcus Baw)]

@clay

I was having trouble with Discourse seeing the plugin when I used a symlink (on MacOS High Sierra). I deleted the symlink and moved the plugin folder into the Discourse hierarchy and everything worked as expected. Maybe this will help others who run into a similar issue.

I’m experiencing the same issue with getting symlinks to work (I’m on Linux) - the ln -s appears to work, but from inside the docker container the path is inaccessible. The plugin works when it is directly copied into the plugins folder, but I like the symlink workflow as it enables a more sensible Git arrangment.

This SO question appears to suggest that symlinks won’t work this way unless we also add the linked-to plugin volume to the docker run command https://stackoverflow.com/questions/38485607/mount-host-directory-with-a-symbolic-link-inside-in-docker-container

Anyone any thoughts on this? What are the pro plugin developers doing for a sensible Git workflow?

[merefield (Robert)]

I’m using symlinks but my dev setup is Docker-frei.

Symlinks are a really nice way of being able to include or exclude plugins on a ‘build’ very quickly without disturbing the codebase.

[pacharanero (Marcus Baw)]

@pacharanero

I’m experiencing the same issue with getting symlinks to work (I’m on Linux) - the ln -s appears to work, but from inside the docker container the path is inaccessible. The plugin works when it is directly copied into the plugins folder, but I like the symlink workflow as it enables a more sensible Git arrangment.

Here’s what I’ve had to do in order to preserve a similar workflow to using symlinks (softlinks):

I edited /bin/docker/boot_dev in Discourse (outside the container) so that the plugin I want to work on is added as a volume and mounted in the /src/plugins/ directory (inside the container).

In my case it looks like this:

docker run -d -p 9405:9405 -p 1080:1080 -p 3000:3000 -p 9292:9292 \
-v "$DATA_DIR:/shared/postgres_data:delegated" \
-v "$SOURCE_DIR:/src:delegated" \ 
-v "/home/marcus/code/discourse/discourse-reflective-learning-plugin:/src/plugins/discourse-reflective-learning-plugin" \
$ENV_ARGS --hostname=discourse --name=discourse_dev --restart=always \
discourse/discourse_dev:release /sbin/boot

I’ve used absolute paths because I couldn’t be bothered to get into relative paths inside Docker and $SOURCE_DIR environment variables, but I’m sure there’s a cleverer way to do this, so that perhaps all your plugins could be in directories at the same level as discourse and it would automagically include them all. Hope this helps someone.

[sam (Sam Saffron)]

@pacharanero

I edited /bin/docker/boot_dev in Discourse

I am totally open to a PR that automatically follows symlinks in plugins/ dir and then smart mounts volumes.