Desarrollando plugins de Discourse - Parte 1 - Crear un plugin básico

[Discourse]

Crear un plugin en Discourse puede ser realmente sencillo, una vez que aprendes algunos peculiaridades. El objetivo de este post es crear un esqueleto de plugin y presentarte lo básico.

Tu entorno de desarrollo

Asegúrate de tener un entorno de desarrollo de Discourse ejecutándose en tu computadora. Recomiendo que uses la guía de configuración adecuada y vuelvas cuando hayas terminado.

plugin.rb

Usa GitHub - discourse/discourse-plugin-skeleton: Template for Discourse plugins · GitHub para crear un esqueleto completo de plugin de Discourse en tu directorio de plugins

El esqueleto ahora viene incluido en el núcleo de Discourse; rake plugin:create[plugin-name] creará un plugin usando el esqueleto.

Cuando Discourse se inicia, busca en el directorio plugins subdirectorios que contengan un archivo plugin.rb. El archivo plugin.rb tiene dos propósitos: es el manifiesto de tu plugin con la información requerida sobre tu plugin, incluyendo: su nombre, información de contacto y una descripción. El segundo propósito es inicializar cualquier código Ruby necesario para ejecutar tu plugin.

En nuestro caso, no añadiremos ningún código Ruby, pero aún necesitamos el plugin.rb. Creemos el directorio basic-plugin con el archivo plugin.rb dentro, con el siguiente contenido:

basic-plugin/plugin.rb

# name: basic-plugin
# about: Un plugin súper simple para demostrar cómo funcionan los plugins
# version: 0.0.1
# authors: Desarrollador de plugins increíble
# url: https://github.com/yourusername/basic-plugin

Una vez que hayas creado este archivo, debes reiniciar tu servidor local y el plugin debería cargarse.

¡Una advertencia importante!

Si estás acostumbrado al desarrollo habitual de Rails, quizás notes que los plugins no son tan cómodos cuando se trata de recargar. En general, cuando hagas cambios en tu plugin, deberías presionar Ctrl+c en el servidor para detenerlo y luego ejecutarlo nuevamente usando bin/dev.

¡Mis cambios no se detectaron!

A veces la caché no se limpia completamente, especialmente cuando creas nuevos archivos o borras archivos antiguos. Para solucionar este problema, elimina tu carpeta tmp y vuelve a iniciar Rails. En una Mac puedes hacerlo con un solo comando: rm -rf tmp; bin/dev.

Verificar que tu plugin se cargó

Una vez que hayas reiniciado tu servidor local, visita la URL /admin/plugins (asegúrate de haber iniciado sesión con una cuenta de administrador primero, ya que solo los administradores pueden ver el registro de plugins).

Si todo funcionó correctamente, deberías ver tu plugin en la lista:

¡Felicidades, acabas de crear tu primer plugin!

Agreguemos algo de JavaScript

Por ahora, tu plugin no hace nada. Agreguemos un archivo JavaScript que muestre una alerta cuando Discourse se cargue. Esto será muy molesto para cualquier usuario y no se recomienda como un plugin real, pero mostrará cómo insertar JavaScript en nuestra aplicación en ejecución.

Crea el siguiente archivo:

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

export default {
  name: "alert",
  initialize() {
    alert("¡Las cajas de alerta son molestas!");
  },
};

Ahora, si reinicias tu servidor local, deberías ver «¡Las cajas de alerta son molestas!» aparecer en la pantalla. (Si no fue así, consulta el encabezado «Mis cambios no se detectaron» más arriba).

Repasemos cómo funcionó esto:

1. Los archivos JavaScript colocados en assets/javascripts/discourse/initializers se ejecutan automáticamente cuando la aplicación de Discourse se carga.

2. Este archivo en particular exporta un objeto, que tiene un name y una función initialize.

3. El name debe ser único, así que simplemente lo llamé alert.

4. La función initialize() se llama cuando la aplicación se carga. En nuestro caso, todo lo que hace es ejecutar nuestro código alert().

¡Ahora eres un desarrollador oficial de plugins de Discourse!

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Más en la serie

Parte 1: Este tema
Parte 2: Salidas de plugins
Parte 3: Configuraciones del sitio
Parte 4: Configuración de git
Parte 5: Interfaces de administración
Parte 6: Pruebas de aceptación
Parte 7: Publica tu plugin

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Este documento tiene control de versiones: sugiere cambios en 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

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@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.