Canvas Plugin Initialization Skill

This skill provides a standardized way to initialize a new plugin in Canvas LMS. It creates a robust starting point with GUI settings, a backend API, a background worker, and a customizable Course Navigation page with permissions.

Features

•GUI (User Interface): Creates a settings_partial that displays a "Hello {{current_user}}" message and basic configuration fields.
•API Backend: Sets up a controller in app/controllers/api/v1/ and registers custom routes.
•Worker Job: Implements a Delayed::Job compatible worker for background tasks.
•Course Navigation: Adds a sample page to the Course menu (sidebar) that shows "Hello {{username}}, welcome to {{coursename}}".
•System Hooks (Canvas Extensions): Demonstrates how to hook into core Canvas logic using Module#prepend (example: Quizzes::Quiz#generate_submission to track quiz starts).
•Granular Permissions: Registers a custom permission (view_<plugin_name>_sample_page) that can be configured in the Course/Account "Permissions" settings.
•Automatic Registration: Updates Gemfile.d/plugins.rb to ensure the plugin is loaded by Canvas.

Usage

1. Initialize a new plugin

Use the init_plugin.sh script to scaffold the plugin.

bash

/bin/bash .agent/skills/canvas-plugin-init/scripts/init_plugin.sh <plugin_name_snake_case>

Example:

bash

/bin/bash .agent/skills/canvas-plugin-init/scripts/init_plugin.sh hello_world

2. File Structure Created

•gems/plugins/<name>/<name>.gemspec: Gem specification.
•gems/plugins/<name>/lib/<name>/engine.rb: Rails Engine, Permission registration, and Course Navigation extension.
•gems/plugins/<name>/app/views/plugins/_<name>_settings.html.erb: Configuration GUI.
•gems/plugins/<name>/app/controllers/api/v1/<name>_controller.rb: API Backend.
•gems/plugins/<name>/app/controllers/course_sample_controller.rb: Course Navigation controller.
•gems/plugins/<name>/app/views/<name>/course_sample/index.html.erb: Course Navigation view.
•gems/plugins/<name>/config/pre_routes.rb: Custom routes.
•gems/plugins/<name>/lib/<name>/worker.rb: Background Worker.

3. Components Overview

Course Navigation Extensions

The skill uses Course.prepend to inject a custom tab into the tabs_available list. The tab only appears if the user has the registered permission for that course.

Permissions

Permissions are registered via Permissions.register in the engine's to_prepare block. They automatically appear in the Canvas Permissions UI under the name provided.

GUI

The settings partial is accessible via Site Admin > Plugins > <Your Plugin Name>.

Requirements

•Canvas LMS environment.
•Sufficient permissions to create files in gems/plugins/ and modify Gemfile.d/plugins.rb.

Troubleshooting

Missing partial plugins/_<plugin_name>_settings

Error:

code

ActionView::MissingTemplate in Plugins#show
Missing partial plugins/_<plugin_name>_settings

Cause: This error occurs when the plugin is registered with a settings_partial in the engine.rb file, but the corresponding partial view file doesn't exist.

Solution: Ensure the settings partial exists at the correct location:

code

gems/plugins/<plugin_name>/app/views/plugins/_<plugin_name>_settings.html.erb

The init_plugin.sh script automatically creates this file. If you're creating a plugin manually or the file is missing, create it with the following structure:

erb

<div class="plugin_settings_<plugin_name>">
  <h3><%= t(:<plugin_name>_title, "<Plugin Name> Settings") %></h3>
  <p><%= t(:<plugin_name>_description, "Configure <plugin name> settings.") %></p>
</div>

<%= fields_for :settings do |f| %>
<table class="formtable">
  <tr>
    <td style="vertical-align: top;"><%= blabel :<plugin_name>, :enabled, :en => "Enable Plugin" %></td>
    <td>
      <%= f.check_box :enabled, :checked => Canvas::Plugin.value_to_boolean(settings[:enabled]) %>
    </td>
  </tr>
  <!-- Add additional settings fields here -->
</table>
<% end %>

Key Points:

•The partial filename must start with an underscore (_)
•The partial must be in the app/views/plugins/ directory (not app/views/<plugin_name>/)
•The settings_partial value in engine.rb should match: "plugins/<plugin_name>_settings" (without underscore or .html.erb extension)
•Use fields_for :settings to ensure form fields are properly namespaced