Desenvolvendo Plugins para o Discourse - Parte 1 - Criando um plugin básico

[Discourse]

Criar um plugin no Discourse pode ser realmente simples, depois que você aprende algumas peculiaridades. O objetivo deste post é criar um plugin modelo (skeleton) e apresentá-lo aos conceitos básicos.

Seu ambiente de desenvolvimento

Certifique-se de ter um ambiente de desenvolvimento do Discourse em execução no seu computador. Recomendo que você use o guia de configuração adequado e volte aqui quando terminar.

plugin.rb

Use GitHub - discourse/discourse-plugin-skeleton: Template for Discourse plugins · GitHub para criar um plugin completo do Discourse com a estrutura básica no seu diretório plugins

A estrutura básica agora está incluída no núcleo do Discourse. rake plugin:create[nome-do-plugin] criará um plugin usando essa estrutura.

Quando o Discourse inicia, ele procura no diretório plugins por subdiretórios que contenham um arquivo plugin.rb. O arquivo plugin.rb tem duas finalidades: é o manifesto do seu plugin, com as informações obrigatórias sobre ele, incluindo nome, informações de contato e descrição. A segunda finalidade é inicializar qualquer código Ruby necessário para executar o plugin.

No nosso caso, não adicionaremos nenhum código Ruby, mas ainda precisamos do plugin.rb. Vamos criar o diretório basic-plugin com o arquivo plugin.rb dentro dele, com o seguinte conteúdo:

basic-plugin/plugin.rb

# name: basic-plugin
# about: Um plugin super simples para demonstrar como os plugins funcionam
# version: 0.0.1
# authors: Awesome Plugin Developer
# url: https://github.com/yourusername/basic-plugin

Depois de criar este arquivo, você deve reiniciar seu servidor local e o plugin deverá ser carregado.

Um detalhe importante!

Se você está acostumado com o desenvolvimento padrão do Rails, pode notar que os plugins não são tão práticos quando se trata de recarregamento. Em geral, quando você faz alterações no seu plugin, deve pressionar Ctrl+c para parar o servidor e, em seguida, executá-lo novamente usando bin/dev.

Minhas alterações não foram reconhecidas!

Às vezes, o cache não é limpo completamente, especialmente quando você cria novos arquivos ou exclui arquivos antigos. Para contornar esse problema, remova sua pasta tmp e inicie o Rails novamente. No Mac, você pode fazer isso com um único comando: rm -rf tmp; bin/dev.

Verificando se seu plugin foi carregado

Depois de reiniciar seu servidor local, visite a URL /admin/plugins (certifique-se de estar logado como uma conta de administrador primeiro, pois apenas administradores podem ver o registro de plugins).

Se tudo funcionou corretamente, você deverá ver seu plugin na lista:

Parabéns, você acabou de criar seu primeiro plugin!

Vamos adicionar algum JavaScript

No momento, seu plugin não faz nada. Vamos adicionar um arquivo JavaScript que exibirá uma caixa de alerta quando o Discourse for carregado. Isso será super irritante para qualquer usuário e não é recomendado como um plugin real, mas mostrará como inserir JavaScript em nossa aplicação em execução.

Crie o seguinte arquivo:

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

export default {
  name: "alert",
  initialize() {
    alert("Caixas de alerta são irritantes!");
  },
};

Agora, se você reiniciar seu servidor local, deverá ver “Caixas de alerta são irritantes!” aparecer na tela. (Se não aparecer, consulte o cabeçalho “Minhas alterações não foram reconhecidas” acima).

Vamos analisar como isso funcionou:

1. Arquivos JavaScript colocados em assets/javascripts/discourse/initializers são executados automaticamente quando a aplicação Discourse é carregada.

2. Este arquivo específico exporta um objeto, que possui um name (nome) e uma função initialize (inicialização).

3. O name precisa ser único, então eu simplesmente o chamei de alert.

4. A função initialize() é chamada quando a aplicação é carregada. No nosso caso, tudo o que ela faz é executar nosso código alert().

Você agora é um desenvolvedor oficial de plugins do Discourse!

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Mais na série

Parte 1: Este tópico
Parte 2: Plugin Outlets
Parte 3: Configurações do Site
Parte 4: Configuração do git
Parte 5: Interfaces de administração
Parte 6: Testes de aceitação
Parte 7: Publique seu plugin

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Este documento é controlado por versão - sugira alterações no 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.