Fetch thread names from ruby when outputting

Author: dalehamel

lib/vernier/output/firefox.rb

@@ -165,6 +165,15 @@ def initialize(ruby_thread_id, profile, categorizer, name:, tid:, samples:, weig
           @tid = tid
           @name = name
 
+          if @name == ""
+            tr = ObjectSpace._id2ref(@ruby_thread_id)
+            if tr && tr.name && !tr.name.empty?
+              @name = tr.name
+            else
+              @name = "UNNAMED [#{@ruby_thread_id}]"
+            end
+          end
+
           timestamps ||= [0] * samples.size
           @samples, @weights, @timestamps = samples, weights, timestamps
           @sample_categories = sample_categories || ([0] * samples.size)

test/output/test_firefox.rb

@@ -151,4 +151,33 @@ def test_custom_intervals
     markers = JSON.parse(output)["threads"].flat_map { _1["markers"]["data"] }
     assert_includes markers, {"type"=>"UserTiming", "entryType"=>"measure", "name"=>"custom"}
   end
+
+
+  def test_thread_names
+    current_name = Thread.current.name
+    unnamed_id = nil
+    result = Vernier.trace do
+      Thread.current.name="main"
+      th1 = Thread.new { sleep 0.01 }
+      unnamed_id = th1.object_id
+      th1.join
+    end
+
+    output = Vernier::Output::Firefox.new(result).output
+
+    assert_valid_firefox_profile(output)
+
+    data = JSON.parse(output)
+    threads = data["threads"]
+    threads.each do |tr|
+      if tr["isMainThread"]
+        assert_equal "main", tr["name"]
+      else
+        assert_equal "UNNAMED [#{unnamed_id}]", tr["name"]
+      end
+    end
+
+  ensure
+    Thread.current.name = current_name
+  end
 end