feat(config): Add option to disable autoconfiguration (#419)

This adds two functions, load_integrations & load_integration(integration) 
that allow Bugsnag integrations to be loaded during runtime.

By default, load_integrations will be run when the bugsnag module is
required. This behaviour can be disabled using the environment variable
BUGSNAG_DISABLE_AUTOCONFIGURE.

lib/bugsnag.rb

@@ -13,6 +13,8 @@
 require "bugsnag/delivery/synchronous"
 require "bugsnag/delivery/thread_queue"
 
+# Rack is not bundled with the other integrations
+# as it doesn't auto-configure when loaded
 require "bugsnag/integrations/rack"
 
 require "bugsnag/middleware/rack_request"
@@ -28,6 +30,7 @@
 
 module Bugsnag
   LOCK = Mutex.new
+  INTEGRATIONS = [:resque, :sidekiq, :mailman, :delayed_job, :shoryuken, :que]
 
   class << self
     ##
@@ -155,13 +158,28 @@ def start_session
     def before_notify_callbacks
       Bugsnag.configuration.request_data[:before_callbacks] ||= []
     end
-  end
-end
 
-require "bugsnag/integrations/railtie" if defined?(Rails::Railtie)
-[:resque, :sidekiq, :mailman, :delayed_job, :shoryuken, :que].each do |integration|
-  begin
-    require "bugsnag/integrations/#{integration}"
-  rescue LoadError
+    # Attempts to load all integrations through auto-discovery
+    def load_integrations
+      require "bugsnag/integrations/railtie" if defined?(Rails::Railtie)
+      INTEGRATIONS.each do |integration|
+        begin
+          require "bugsnag/integrations/#{integration}"
+        rescue LoadError
+        end
+      end
+    end
+
+    # Load a specific integration
+    def load_integration(integration)
+      integration = :railtie if integration == :rails
+      if INTEGRATIONS.include?(integration) || integration == :railtie
+        require "bugsnag/integrations/#{integration}"
+      else
+        configuration.debug("Integration #{integration} is not currently supported")
+      end
+    end
   end
 end
+
+Bugsnag.load_integrations unless ENV["BUGSNAG_DISABLE_AUTOCONFIGURE"]

spec/bugsnag_spec.rb

@@ -16,4 +16,71 @@
       expect(Bugsnag.configuration.logger).to have_received(:warn)
     end
   end
+
+  describe 'loading integrations' do
+    before do
+      module Kernel
+        REQUIRED = []
+        alias_method :old_require, :require
+        def require(path)
+          if path.include?("bugsnag/integrations/")
+            REQUIRED << path
+          else
+            old_require(path)
+          end
+        end
+      end
+    end
+
+    it 'attempts to load integrations' do
+      Kernel::REQUIRED = []
+      ENV["BUGSNAG_DISABLE_AUTOCONFIGURE"] = nil
+      load "./lib/bugsnag.rb"
+      Bugsnag::INTEGRATIONS.each do |integration|
+        expect(Kernel::REQUIRED).to include("bugsnag/integrations/#{integration}")
+      end
+    end
+
+    it 'does not load integrations when BUGSNAG_DISABLE_AUTOCONFIGURE is true' do
+      Kernel::REQUIRED = []
+      ENV["BUGSNAG_DISABLE_AUTOCONFIGURE"] = 'true'
+      load "./lib/bugsnag.rb"
+      expect(Kernel::REQUIRED).to eq(["bugsnag/integrations/rack"])
+    end
+
+    it 'loads all integrations if requested' do
+      Kernel::REQUIRED = []
+      expect(Kernel::REQUIRED).to eq([])
+      Bugsnag.load_integrations
+      Bugsnag::INTEGRATIONS.each do |integration|
+        expect(Kernel::REQUIRED).to include("bugsnag/integrations/#{integration}")
+      end
+    end
+
+    it 'loads singular integrations' do
+      Kernel::REQUIRED = []
+      expect(Kernel::REQUIRED).to eq([])
+      Bugsnag::INTEGRATIONS.each do |integration|
+        Kernel::REQUIRED = []
+        Bugsnag.load_integration(integration)
+        expect(Kernel::REQUIRED).to include("bugsnag/integrations/#{integration}")
+      end
+    end
+
+    it 'loads railtie for :rails or :railtie' do
+      Kernel::REQUIRED = []
+      Bugsnag.load_integration(:rails)
+      expect(Kernel::REQUIRED).to include("bugsnag/integrations/railtie")
+      Kernel::REQUIRED = []
+      Bugsnag.load_integration(:railtie)
+      expect(Kernel::REQUIRED).to include("bugsnag/integrations/railtie")
+    end
+
+    after do
+      module Kernel
+        alias_method :require, :old_require
+      end
+      Kernel.send(:remove_const, :REQUIRED)
+    end
+  end
 end