Add the action instance to the request environment (#446)

This is useful for third party instrumentation tools like AppSignal.

---------

Co-authored-by: Tim Riley <[email protected]>

lib/hanami/action.rb

@@ -332,6 +332,10 @@ def call(env)
         _handle_exception(request, response, exception)
       end
 
+      # Before finishing, put ourself into the Rack env for third-party instrumentation tools to
+      # integrate with actions
+      env[ACTION_INSTANCE] = self
+
       finish(request, response, halted)
     end
 

lib/hanami/action/constants.rb

@@ -245,5 +245,9 @@ class Action
     # @since 2.0.0
     # @api private
     DEFAULT_CHARSET = "utf-8"
+
+    # @since 2.2.0
+    # @api private
+    ACTION_INSTANCE = "hanami.action_instance"
   end
 end

spec/support/fixtures.rb

@@ -587,7 +587,8 @@ def handle(_req, _res)
 
 class ParamsAction < Hanami::Action
   def handle(req, res)
-    res.body = req.params.to_h.inspect
+    params = req.params.to_h
+    res.body = params.inspect
   end
 end
 

spec/unit/hanami/action_spec.rb

@@ -21,6 +21,14 @@
       expect(response.body).to    eq(["Hi from TestAction!"])
     end
 
+    it "sets the action instance on the request environment object" do
+      action = CallAction.new
+      env = {}
+      action.call(env)
+
+      expect(env[Hanami::Action::ACTION_INSTANCE]).to eq(action)
+    end
+
     context "when an exception isn't handled" do
       it "should raise an actual exception" do
         expect { UncheckedErrorCallAction.new.call({}) }.to raise_error(RuntimeError)