Entwicklung von Discourse-Plugins – Teil 1: Ein einfaches Plugin erstellen

[Discourse]

Einen Plugin in Discourse zu erstellen, kann wirklich einfach sein, sobald man ein paar Eigenheiten kennt. Ziel dieses Beitrags ist es, ein Grundgerüst für ein Plugin zu erstellen und Sie mit den Grundlagen vertraut zu machen.

Ihre Entwicklungsumgebung

Stellen Sie sicher, dass Sie eine Discourse-Entwicklungsumgebung auf Ihrem Computer laufen haben. Ich empfehle Ihnen, den entsprechenden Einrichtungsleitfaden zu verwenden und erst zurückzukehren, wenn Sie fertig sind.

plugin.rb

Verwenden Sie GitHub - discourse/discourse-plugin-skeleton: Template for Discourse plugins · GitHub, um ein vollständiges Discourse-Plugin-Grundgerüst in Ihrem Plugin-Verzeichnis zu erstellen

Das Grundgerüst ist jetzt in Discourse-Kern enthalten. rake plugin:create[plugin-name] erstellt ein Plugin mit dem Grundgerüst.

Wenn Discourse startet, sucht es im plugins-Verzeichnis nach Unterverzeichnissen, die eine plugin.rb-Datei enthalten. Die plugin.rb-Datei hat zwei Zwecke: Sie dient als Manifest für Ihr Plugin mit den erforderlichen Informationen über Ihr Plugin, einschließlich: Name, Kontaktinformationen und Beschreibung. Der zweite Zweck besteht darin, den für die Ausführung Ihres Plugins erforderlichen Ruby-Code zu initialisieren.

In unserem Fall fügen wir keinen Ruby-Code hinzu, aber wir benötigen trotzdem die plugin.rb. Erstellen wir das Verzeichnis basic-plugin mit der Datei plugin.rb darin, mit folgendem Inhalt:

basic-plugin/plugin.rb

# name: basic-plugin
# about: Ein super einfaches Plugin, um zu demonstrieren, wie Plugins funktionieren
# version: 0.0.1
# authors: Awesome Plugin Developer
# url: https://github.com/yourusername/basic-plugin

Sobald Sie diese Datei erstellt haben, sollten Sie Ihren lokalen Server neu starten, und das Plugin sollte geladen werden.

Eine wichtige Fallstrick!

Wenn Sie an eine normale Rails-Entwicklung gewöhnt sind, werden Sie möglicherweise feststellen, dass Plugins beim Neuladen nicht ganz so angenehm sind. Im Allgemeinen sollten Sie beim Ändern Ihres Plugins den Server mit Strg+c stoppen und ihn dann erneut mit bin/dev starten.

Meine Änderungen wurden nicht übernommen!

Manchmal wird der Cache nicht vollständig geleert, insbesondere wenn Sie neue Dateien erstellen oder alte löschen. Um dieses Problem zu umgehen, entfernen Sie Ihren tmp-Ordner und starten Sie Rails neu. Auf einem Mac können Sie dies mit einem Befehl tun: rm -rf tmp; bin/dev.

Überprüfen, ob Ihr Plugin geladen wurde

Nachdem Sie Ihren lokalen Server neu gestartet haben, besuchen Sie die URL /admin/plugins (stellen Sie sicher, dass Sie sich zuerst als Administratorkonto angemeldet haben, da nur Administratoren das Plugin-Register sehen können).

Wenn alles funktioniert hat, sollten Sie Ihr Plugin in der Liste sehen:

Herzlichen Glückwunsch, Sie haben gerade Ihr erstes Plugin erstellt!

Fügen wir etwas JavaScript hinzu

Momentan macht Ihr Plugin nichts. Fügen wir eine JavaScript-Datei hinzu, die beim Laden von Discourse ein Alert-Fenster öffnet. Dies wird für jeden Benutzer sehr störend sein und wird nicht als echtes Plugin empfohlen, zeigt aber, wie JavaScript in unsere laufende Anwendung eingefügt wird.

Erstellen Sie die folgende Datei:

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

export default {
  name: "alert",
  initialize() {
    alert("Alert-Fenster sind nervig!");
  },
};

Wenn Sie jetzt Ihren lokalen Server neu starten, sollten Sie „Alert-Fenster sind nervig!

[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.