Développement de plugins Discourse - Partie 1 - Créer un plugin basique

[Discourse]

Créer une extension (plugin) pour Discourse peut être très simple une fois que vous avez appris quelques particularités. L’objectif de ce billet est de créer un squelette d’extension et de vous initier aux bases.

Votre environnement de développement

Assurez-vous d’avoir un environnement de développement Discourse fonctionnel sur votre ordinateur. Je vous recommande d’utiliser le guide d’installation approprié et de revenir lorsque vous avez terminé.

plugin.rb

Utilisez GitHub - discourse/discourse-plugin-skeleton: Template for Discourse plugins pour créer un squelette d’extension Discourse complet dans votre répertoire plugins

Le squelette est maintenant intégré au cœur de Discourse, rake plugin:create[nom-de-l-extension] créera une extension en utilisant le squelette

Lorsque Discourse démarre, il recherche dans le répertoire plugins des sous-répertoires contenant un fichier plugin.rb. Le fichier plugin.rb a deux objectifs : il sert de manifeste pour votre extension avec les informations requises à son sujet, y compris : son nom, les coordonnées et une description. Le second objectif est d’initialiser tout code ruby nécessaire pour exécuter votre extension.

Dans notre cas, nous n’ajouterons aucun code ruby, mais nous avons toujours besoin du plugin.rb. Créons le répertoire basic-plugin avec le fichier plugin.rb à l’intérieur, contenant ce qui suit :

basic-plugin/plugin.rb

# name: basic-plugin
# about: Une extension super simple pour démontrer le fonctionnement des extensions
# version: 0.0.1
# authors: Awesome Plugin Developer
# url: https://github.com/yourusername/basic-plugin

Une fois que vous avez créé ce fichier, vous devriez redémarrer votre serveur local et l’extension devrait être chargée.

Un piège important !

Si vous êtes habitué au développement Rails classique, vous pourriez remarquer que les extensions ne sont pas aussi pratiques en ce qui concerne le rechargement. En général, lorsque vous apportez des modifications à votre extension, vous devez arrêter le serveur en appuyant sur Ctrl+c, puis le redémarrer en utilisant bin/ember-cli -u.

Mes modifications n’ont pas été prises en compte !

Parfois, le cache n’est pas entièrement vidé, surtout lorsque vous créez de nouveaux fichiers ou supprimez d’anciens fichiers. Pour contourner ce problème, supprimez votre dossier tmp et redémarrez Rails. Sur un Mac, vous pouvez le faire en une seule commande : rm -rf tmp; bin/ember-cli -u.

Vérifier que votre extension a été chargée

Une fois que vous avez redémarré votre serveur local, visitez l’URL /admin/plugins (assurez-vous d’être connecté avec un compte administrateur au préalable, car seuls les administrateurs peuvent voir le registre des extensions).

Si tout a fonctionné, vous devriez voir votre extension dans la liste :

Félicitations, vous venez de créer votre première extension !

Ajoutons du Javascript

Actuellement, votre extension ne fait rien. Ajoutons un fichier javascript qui affichera une boîte d’alerte lorsque Discourse se charge. Ce sera super ennuyeux pour tout utilisateur et n’est pas recommandé comme extension réelle, mais cela montrera comment insérer du Javascript dans notre application en cours d’exécution.

Créez le fichier suivant :

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

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

Maintenant, si vous redémarrez votre serveur local, vous devriez voir “alert boxes are annoying!” apparaître à l’écran. (Si ce n’est pas le cas, consultez le titre “Mes modifications n’ont pas été prises en compte” ci-dessus).

Décortiquons comment cela a fonctionné :

1. Les fichiers Javascript placés dans assets/javascripts/discourse/initializers sont exécutés automatiquement lorsque l’application Discourse se charge.

2. Ce fichier particulier exporte un seul objet, qui possède un name et une fonction initialize.

3. Le name doit être unique, je l’ai donc simplement appelé alert.

4. La fonction initialize() est appelée lorsque l’application se charge. Dans notre cas, tout ce qu’elle fait est d’exécuter notre code alert().

Vous êtes maintenant un développeur d’extensions Discourse officiel !

---

Plus dans la série

Partie 1 : Ce sujet
Partie 2 : Passerelles d’extension (Plugin Outlets)
Partie 3 : Paramètres du site (Site Settings)
Partie 4 : Configuration Git
Partie 5 : Interfaces d’administration
Partie 6 : Tests d’acceptation
Partie 7 : Publiez votre extension

---

Ce document est contrôlé par version - suggérez des modifications sur github.

[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:

Raise an error if a widget doesn't have a key but uses state

[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.