Don’t push to client layer if not tracking

- This will resolve a potential issue with client side logic including
events that we shouldn’t be linking together. The thinking is that this
would be fine without this, but this future proofs things a bit more.

app/experiments/application_experiment.rb

@@ -10,9 +10,10 @@ class ApplicationExperiment < Gitlab::Experiment # rubocop:disable Gitlab/Namesp
   end
 
   def publish(_result = nil)
+    return unless should_track? # don't track events for excluded contexts
+
     track(:assignment) # track that we've assigned a variant for this context
 
-    # push the experiment data to the client
     begin
       Gon.push({ experiment: { name => signature } }, true) # push the experiment data to the client
     rescue NoMethodError

spec/experiments/application_experiment_spec.rb

@@ -58,6 +58,15 @@ RSpec.describe ApplicationExperiment, :experiment do
   end
 
   describe "publishing results" do
+    it "doesn't track or push data to the client if we shouldn't track", :snowplow do
+      allow(subject).to receive(:should_track?).and_return(false)
+      expect(Gon).not_to receive(:push)
+
+      subject.publish(:action)
+
+      expect_no_snowplow_event
+    end
+
     it "tracks the assignment" do
       expect(subject).to receive(:track).with(:assignment)