Sviluppo di Plugin Discourse - Parte 1 - Creare un plugin base

[Discourse]

Creare un plugin per Discourse può essere davvero semplice, una volta che si conoscono alcune particolarità. L’obiettivo di questo post è creare una struttura base di un plugin e presentarti le nozioni fondamentali.

Il tuo ambiente di sviluppo

Assicurati di avere un ambiente di sviluppo di Discourse in esecuzione sul tuo computer. Ti consiglio di seguire la guida di installazione appropriata e di tornare qui una volta terminato.

plugin.rb

Usa GitHub - discourse/discourse-plugin-skeleton: Template for Discourse plugins · GitHub per creare una struttura completa di un plugin Discourse nella tua directory dei plugin

La struttura è ora inclusa nel codice principale di Discourse, rake plugin:create[nome-plugin] creerà un plugin utilizzando la struttura

All’avvio, Discourse cerca nella directory plugins le sottodirectory che contengono un file plugin.rb. Il file plugin.rb ha due scopi: è il manifesto del tuo plugin con le informazioni richieste sul plugin stesso, tra cui: il suo nome, i contatti e una descrizione. Il secondo scopo è inizializzare qualsiasi codice Ruby necessario per eseguire il plugin.

Nel nostro caso, non aggiungeremo alcun codice Ruby, ma abbiamo comunque bisogno del file plugin.rb. Creiamo la directory basic-plugin con il file plugin.rb al suo interno, con il seguente contenuto:

basic-plugin/plugin.rb

# name: basic-plugin
# about: Un plugin super semplice per dimostrare come funzionano i plugin
# version: 0.0.1
# authors: Sviluppatore Plugin Fantastico
# url: https://github.com/tuonomeutente/basic-plugin

Una volta creato questo file, dovrai riavviare il tuo server locale e il plugin dovrebbe essere caricato.

Un importante trucco!

Se sei abituato allo sviluppo Rails standard, potresti notare che i plugin non sono altrettanto facili quando si tratta di ricaricamento. In generale, quando apporti modifiche al tuo plugin, dovresti premere Ctrl+c per arrestare il server, quindi eseguirlo di nuovo con bin/dev.

I miei cambiamenti non sono stati rilevati!

A volte la cache non viene cancellata completamente, specialmente quando crei nuovi file o elimini file vecchi. Per risolvere questo problema, rimuovi la tua cartella tmp e avvia di nuovo Rails. Su un Mac puoi farlo con un unico comando: rm -rf tmp; bin/dev.

Verifica che il tuo plugin sia stato caricato

Una volta riavviato il tuo server locale, visita l’URL /admin/plugins (assicurati di essere accedere come account amministratore prima, poiché solo gli amministratori possono vedere il registro dei plugin).

Se tutto ha funzionato, dovresti vedere il tuo plugin nell’elenco:

Congratulazioni, hai appena creato il tuo primo plugin!

Aggiungiamo del Javascript

Al momento il tuo plugin non fa nulla. Aggiungiamo un file Javascript che farà apparire una finestra di avviso quando Discourse si carica. Questo sarà estremamente fastidioso per qualsiasi utente e non è consigliato come plugin reale, ma mostrerà come inserire Javascript nella nostra applicazione in esecuzione.

Crea il seguente file:

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

export default {
  name: "alert",
  initialize() {
    alert("le finestre di avviso sono fastidiose!");
  },
};

Ora, se riavvii il tuo server locale, dovresti vedere apparire “le finestre di avviso sono fastidiose!” sullo schermo. (Se non è così, vedi la sezione “I miei cambiamenti non sono stati rilevati” sopra).

Analizziamo come ha funzionato:

1. I file Javascript posizionati in assets/javascripts/discourse/initializers vengono eseguiti automaticamente quando l’applicazione Discourse si carica.

2. Questo particolare file export un oggetto, che ha un name e una funzione initialize.

3. Il name deve essere univoco, quindi l’ho chiamato semplicemente alert.

4. La funzione initialize() viene chiamata quando l’applicazione si carica. Nel nostro caso, esegue solo il nostro codice alert().

Ora sei uno sviluppatore di plugin Discourse ufficiale!

---

Più nella serie

Parte 1: Questo argomento
Parte 2: Plugin Outlets
Parte 3: Site Settings
Parte 4: git setup
Parte 5: Admin interfaces
Parte 6: Acceptance tests
Parte 7: Publish your plugin

---

Questo documento è sotto controllo versione - suggerisci modifiche su 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:

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.