Fix performance breakdown not being sent when a group has 0 value

The backend rejects performance breakdown if one of the groups is 0 with this
message: `routes: sum <= 0`.

Not every route executes database requests, therefore, many routes won't have a
chance to send their `view` data.

CHANGELOG.md

@@ -5,12 +5,14 @@ Airbrake Changelog
 
 * Fixed the Rails performance breakdown hook not maintaining performance
   precision ([#936](https://github.com/airbrake/airbrake/pull/936))
+* Fix Rails performance breakdown not being sent if one of the groups is zero
+  ([#935](https://github.com/airbrake/airbrake/pull/935))
 
 ### [v8.3.1][v8.3.1] (March 11, 2019)
 
 * Fixes `TypeError` in the `ActionControllerPerformanceBreakdownSubscriber` when
   it tries to pass `nil` as a `db` or `view` value
-  ([#932](https://github.com/airbrake/airbrake/pull/932)
+  ([#932](https://github.com/airbrake/airbrake/pull/932))
 
 ### [v8.3.0][v8.3.0] (March 11, 2019)
 

lib/airbrake/rails/action_controller_performance_breakdown_subscriber.rb

@@ -10,18 +10,29 @@ def call(*args)
         payload = event.payload
 
         routes.each do |route, method|
+          next if (groups = build_groups(payload)).none?
+
           Airbrake.notify_performance_breakdown(
             method: method,
             route: route,
             response_type: payload[:format],
-            groups: {
-              db: payload[:db_runtime] || 0,
-              view: payload[:view_runtime] || 0
-            },
+            groups: groups,
             start_time: event.time
           )
         end
       end
+
+      def build_groups(payload)
+        groups = {}
+
+        db_runtime = payload[:db_runtime] || 0
+        groups[:db] = db_runtime if db_runtime > 0
+
+        view_runtime = payload[:view_runtime] || 0
+        groups[:view] = view_runtime if view_runtime > 0
+
+        groups
+      end
     end
   end
 end

spec/apps/rails/dummy_app.rb

@@ -30,6 +30,7 @@ class DummyApp < Rails::Application
   routes.append do
     get '/' => 'dummy#index'
     get '/crash' => 'dummy#crash'
+    get '/breakdown' => 'dummy#breakdown'
     get '/notify_airbrake_helper' => 'dummy#notify_airbrake_helper'
     get '/notify_airbrake_sync_helper' => 'dummy#notify_airbrake_sync_helper'
     get '/active_record_after_commit' => 'dummy#active_record_after_commit'
@@ -100,7 +101,8 @@ class DummyController < ActionController::Base
       'dummy/active_record_after_rollback.html.erb' => 'active_record_after_rollback',
       'dummy/active_job.html.erb' => 'active_job',
       'dummy/resque.html.erb' => 'resque',
-      'dummy/delayed_job.html.erb' => 'delayed_job'
+      'dummy/delayed_job.html.erb' => 'delayed_job',
+      'dummy/breakdown.html.erb' => 'breakdown'
     )
   ]
 
@@ -111,6 +113,11 @@ def crash
     raise AirbrakeTestError
   end
 
+  def breakdown
+    Book.create(title: 'breakdown')
+    Book.all
+  end
+
   def notify_airbrake_helper
     notify_airbrake(AirbrakeTestError.new)
   end

spec/integration/rails/rails_spec.rb

@@ -296,17 +296,14 @@
     it "sends performance breakdown info to Airbrake" do
       expect(Airbrake).to receive(:notify_performance_breakdown).with(
         hash_including(
-          route: '/crash(.:format)',
+          route: '/breakdown(.:format)',
           method: 'GET',
           response_type: :html,
-          groups: {
-            db: anything,
-            view: anything
-          }
+          groups: hash_including(db: an_instance_of(Float))
         )
       ).at_least(:once)
 
-      get '/crash'
+      get '/breakdown'
     end
   end
 end

spec/unit/rails/action_controller_performance_breakdown_subscriber_spec.rb

@@ -55,13 +55,13 @@
     context "and when view_runtime is nil" do
       before { event.payload[:view_runtime] = nil }
 
-      it "sets the view group runtime to 0" do
+      it "omits view_runtime" do
         expect(Airbrake).to receive(:notify_performance_breakdown).with(
           hash_including(
             route: '/test-route',
             method: 'GET',
             response_type: :html,
-            groups: { db: 0.5, view: 0 }
+            groups: { db: 0.5 }
           )
         )
         subject.call([])
@@ -71,17 +71,61 @@
     context "and when db_runtime is nil" do
       before { event.payload[:db_runtime] = nil }
 
-      it "sets the view group runtime to 0" do
+      it "omits db_runtime" do
         expect(Airbrake).to receive(:notify_performance_breakdown).with(
           hash_including(
             route: '/test-route',
             method: 'GET',
             response_type: :html,
-            groups: { db: 0, view: 0.5 }
+            groups: { view: 0.5 }
           )
         )
         subject.call([])
       end
     end
+
+    context "when db_runtime is zero" do
+      before { event.payload[:db_runtime] = 0 }
+
+      it "omits db_runtime" do
+        expect(Airbrake).to receive(:notify_performance_breakdown).with(
+          hash_including(
+            route: '/test-route',
+            method: 'GET',
+            response_type: :html,
+            groups: { view: 0.5 }
+          )
+        )
+        subject.call([])
+      end
+    end
+
+    context "when view_runtime is zero" do
+      before { event.payload[:view_runtime] = 0 }
+
+      it "omits view_runtime" do
+        expect(Airbrake).to receive(:notify_performance_breakdown).with(
+          hash_including(
+            route: '/test-route',
+            method: 'GET',
+            response_type: :html,
+            groups: { db: 0.5 }
+          )
+        )
+        subject.call([])
+      end
+    end
+
+    context "when db_runtime and view_runtime are both zero" do
+      before do
+        event.payload[:db_runtime] = 0
+        event.payload[:view_runtime] = 0
+      end
+
+      it "doesn't notify Airbrake" do
+        expect(Airbrake).not_to receive(:notify_performance_breakdown)
+        subject.call([])
+      end
+    end
   end
 end