Feature: Add service worker registration method to plugin API

app/assets/javascripts/discourse/initializers/android-app-banner-service-worker.js.es6

@@ -1,16 +0,0 @@
-// Android Chrome App Banner requires at least **one** service worker to be instantiate and https.
-// After Discourse starts to use service workers for other stuff (like mobile notification, offline mode, or ember)
-// we can ditch this.
-
-export default {
-  name: 'android-app-banner-service-worker',
-
-  initialize(container) {
-    const caps = container.lookup('capabilities:main');
-    const isSecure = document.location.protocol === 'https:';
-
-    if (isSecure && caps.isAndroid && 'serviceWorker' in navigator) {
-        navigator.serviceWorker.register(Discourse.BaseUri + '/service-worker.js');
-    }
-  }
-};

app/assets/javascripts/discourse/initializers/register-service-worker.js.es6

@@ -0,0 +1,12 @@
+export default {
+  name: 'register-service-worker',
+
+  initialize() {
+    const isSecure = (document.location.protocol === 'https:') ||
+      (location.hostname === "localhost");
+
+    if (isSecure && ('serviceWorker' in navigator)) {
+      navigator.serviceWorker.register(`${Discourse.BaseUri}/service-worker.js`);
+    }
+  }
+};

app/assets/javascripts/service-worker.js.erb

@@ -1,15 +1,13 @@
-/*
- I'm here to support Google Chrome App Banner on Android
- */
-
 'use strict';
 
 // Incrementing CACHE_VERSION will kick off the install event and force previously cached
 // resources to be cached again.
 const CACHE_VERSION = 1;
-let CURRENT_CACHES = {
+
+const CURRENT_CACHES = {
   offline: 'offline-v' + CACHE_VERSION
 };
+
 const OFFLINE_URL = 'offline.html';
 
 function createCacheBustedRequest(url) {
@@ -23,7 +21,7 @@ function createCacheBustedRequest(url) {
 
   // If {cache: 'reload'} didn't have any effect, append a cache-busting URL parameter instead.
   let bustedUrl = new URL(url, self.location.href);
-  bustedUrl.search += (bustedUrl.search ? '&' : '') + 'cachebust=' + Date.now();
+  bustedUrl.search += `${(bustedUrl.search ? '&' : '')}cachebust=${Date.now()}`;
   return new Request(bustedUrl);
 }
 
@@ -88,3 +86,7 @@ self.addEventListener('fetch', event => {
   // event.respondWith(). If no fetch handlers call event.respondWith(), the request will be
   // handled by the browser as if there were no service worker involvement.
 });
+
+<% DiscoursePluginRegistry.service_workers.each do |js| %>
+<%=raw "#{File.read(js)}" %>
+<% end %>

app/controllers/static_controller.rb

@@ -4,7 +4,7 @@ require_dependency 'file_helper'
 class StaticController < ApplicationController
 
   skip_before_action :check_xhr, :redirect_to_login_if_required
-  skip_before_action :verify_authenticity_token, only: [:brotli_asset, :cdn_asset, :enter, :favicon]
+  skip_before_action :verify_authenticity_token, only: [:brotli_asset, :cdn_asset, :enter, :favicon, :service_worker_asset]
 
   PAGES_WITH_EMAIL_PARAM = ['login', 'password_reset', 'signup']
 
@@ -143,6 +143,14 @@ class StaticController < ApplicationController
     serve_asset
   end
 
+  def service_worker_asset
+    respond_to do |format|
+      format.js do
+        render plain: Rails.application.assets["service-worker.js"].to_s
+      end
+    end
+  end
+
   protected
 
   def serve_asset(suffix = nil)

config/routes.rb

@@ -687,6 +687,8 @@ Discourse::Application.routes.draw do
   post "draft" => "draft#update"
   delete "draft" => "draft#destroy"
 
+  get "service-worker" => "static#service_worker_asset", format: :js
+
   get "cdn_asset/:site/*path" => "static#cdn_asset", format: false
   get "brotli_asset/*path" => "static#brotli_asset", format: false
 

lib/discourse_plugin_registry.rb

@@ -5,6 +5,7 @@ class DiscoursePluginRegistry
 
   class << self
     attr_writer :javascripts
+    attr_writer :service_workers
     attr_writer :admin_javascripts
     attr_writer :stylesheets
     attr_writer :mobile_stylesheets
@@ -24,6 +25,10 @@ class DiscoursePluginRegistry
       @javascripts ||= Set.new
     end
 
+    def service_workers
+      @service_workers ||= Set.new
+    end
+
     def asset_globs
       @asset_globs ||= Set.new
     end
@@ -79,6 +84,10 @@ class DiscoursePluginRegistry
     self.class.javascripts << filename
   end
 
+  def self.register_service_worker(filename, options = {})
+    self.service_workers << filename
+  end
+
   def register_css(filename)
     self.class.stylesheets << filename
   end
@@ -166,6 +175,10 @@ class DiscoursePluginRegistry
     self.class.javascripts
   end
 
+  def service_workers
+    self.class.service_workers
+  end
+
   def stylesheets
     self.class.stylesheets
   end
@@ -188,6 +201,7 @@ class DiscoursePluginRegistry
 
   def self.clear
     self.javascripts = nil
+    self.service_workers = nil
     self.stylesheets = nil
     self.mobile_stylesheets = nil
     self.desktop_stylesheets = nil
@@ -197,6 +211,7 @@ class DiscoursePluginRegistry
 
   def self.reset!
     javascripts.clear
+    service_workers.clear
     admin_javascripts.clear
     stylesheets.clear
     mobile_stylesheets.clear

lib/plugin/instance.rb

@@ -29,6 +29,7 @@ class Plugin::Instance
    :color_schemes,
    :initializers,
    :javascripts,
+   :service_workers,
    :styles,
    :themes].each do |att|
     class_eval %Q{
@@ -332,6 +333,13 @@ class Plugin::Instance
     assets << [full_path, opts]
   end
 
+  def register_service_worker(file, opts = nil)
+    service_workers << [
+      File.join(File.dirname(path), 'assets', file),
+      opts
+    ]
+  end
+
   def register_color_scheme(name, colors)
     color_schemes << { name: name, colors: colors }
   end
@@ -420,6 +428,8 @@ JS
 
     register_assets! unless assets.blank?
 
+    register_service_workers!
+
     seed_data.each do |key, value|
       DiscoursePluginRegistry.register_seed_data(key, value)
     end
@@ -516,6 +526,12 @@ JS
     end
   end
 
+  def register_service_workers!
+    service_workers.each do |asset, opts|
+      DiscoursePluginRegistry.register_service_worker(asset, opts)
+    end
+  end
+
   private
 
   def write_asset(path, contents)

spec/components/discourse_plugin_registry_spec.rb

@@ -92,6 +92,25 @@ describe DiscoursePluginRegistry do
     end
   end
 
+  context '.register_service_worker' do
+    let(:registry) { DiscoursePluginRegistry }
+
+    before do
+      registry.register_service_worker('hello.js')
+    end
+
+    after do
+      registry.reset!
+    end
+
+    it "should register the file once" do
+      2.times { registry.register_service_worker('hello.js') }
+
+      expect(registry.service_workers.size).to eq(1)
+      expect(registry.service_workers).to include('hello.js')
+    end
+  end
+
   context '.register_archetype' do
     it "delegates archetypes to the Archetype component" do
       Archetype.expects(:register).with('threaded', hello: 123)

spec/components/plugin/instance_spec.rb

@@ -95,6 +95,18 @@ describe Plugin::Instance do
     end
   end
 
+  context "register service worker" do
+    it "populates the DiscoursePluginRegistry" do
+      plugin = Plugin::Instance.new nil, "/tmp/test.rb"
+      plugin.register_service_worker("test.js")
+      plugin.register_service_worker("test2.js")
+
+      plugin.send :register_service_workers!
+
+      expect(DiscoursePluginRegistry.service_workers.count).to eq(2)
+    end
+  end
+
   context "activate!" do
     it "can activate plugins correctly" do
       plugin = Plugin::Instance.new