Decrease retained object allocations in the reporter

lib/buildkite/test_collector/cucumber_plugin/trace.rb

@@ -2,28 +2,33 @@
 
 module Buildkite::TestCollector::CucumberPlugin
   class Trace < Buildkite::TestCollector::Trace
-    attr_accessor :scenario, :failure_reason, :failure_expanded
+    attr_accessor :failure_reason, :failure_expanded
     attr_reader :history, :tags, :location_prefix
 
     FILE_PATH_REGEX = /^(.*?\.(rb|feature))/
 
     def initialize(scenario, history:, failure_reason: nil, failure_expanded: [], tags: nil, location_prefix: nil)
-      @scenario         = scenario
       @history          = history
       @failure_reason   = failure_reason
       @failure_expanded = failure_expanded
       @tags             = tags
       @location_prefix  = location_prefix
+
+      # Extract all data eagerly to allow GC of the scenario object
+      @result = if scenario.passed?
+                  'passed'
+                elsif scenario.failed?
+                  'failed'
+                else
+                  'skipped'
+                end
+      @name = scenario.name
+      @location = scenario.location&.to_s
+      @file_name = @location&.to_s[FILE_PATH_REGEX]
     end
 
     def result
-      if scenario.passed?
-        'passed'
-      elsif scenario.failed?
-        'failed'
-      else
-        'skipped'
-      end
+      @result
     end
 
     private
@@ -41,15 +46,15 @@ def scope
     end
 
     def name
-      scenario.name
+      @name
     end
 
     def location
-      scenario.location&.to_s
+      @location
     end
 
     def file_name
-      @file_name ||= location&.to_s[FILE_PATH_REGEX]
+      @file_name
     end
   end
 end

lib/buildkite/test_collector/minitest_plugin/reporter.rb

@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 module Buildkite::TestCollector::MinitestPlugin
-  class Reporter < Minitest::StatisticsReporter
+  class Reporter < Minitest::Reporter
     def initialize(io, options)
       super
       @io = io

lib/buildkite/test_collector/minitest_plugin/trace.rb

@@ -2,8 +2,6 @@
 
 module Buildkite::TestCollector::MinitestPlugin
   class Trace < Buildkite::TestCollector::Trace
-    attr_accessor :example
-    attr_writer :failure_reason, :failure_expanded
     attr_reader :history
     attr_reader :location_prefix
     attr_reader :tags
@@ -18,28 +16,45 @@ class Trace < Buildkite::TestCollector::Trace
     FILE_PATH_REGEX = /^(.*?\.(rb|feature))/
 
     def initialize(example, history:, tags: nil, trace: nil, location_prefix: nil)
-      @example = example
       @history = history
       @tags = tags
       @location_prefix = location_prefix
+
+      # Extract all data eagerly to allow GC of the test object
+      @source_location = example.method(example.name).source_location
+      @result = RESULT_CODES[example.result_code]
+      @scope = example.class.name
+      @name = example.name
+      @failure_reason = strip_invalid_utf8_chars(example.failure&.message)&.split("\n")&.first
+      @failure_expanded = example.failures.map.with_index do |failure, index|
+        # remove the first line of message from the first failure
+        # to avoid duplicate line in Test Analytics UI
+        messages = strip_invalid_utf8_chars(failure.message).split("\n")
+        messages = messages[1..-1] if index.zero?
+
+        {
+          expanded: messages,
+          backtrace: failure.backtrace
+        }
+      end
     end
 
     def result
-      RESULT_CODES[example.result_code]
+      @result
     end
 
     def source_location
-      @source_location ||= example.method(example.name).source_location
+      @source_location
     end
 
     private
 
     def scope
-      example.class.name
+      @scope
     end
 
     def name
-      example.name
+      @name
     end
 
     def location
@@ -65,21 +80,11 @@ def project_dir
     end
 
     def failure_reason
-      @failure_reason ||= strip_invalid_utf8_chars(example.failure&.message)&.split("\n")&.first
+      @failure_reason
     end
 
     def failure_expanded
-      @failure_expanded ||= example.failures.map.with_index do |failure, index|
-        # remove the first line of message from the first failure
-        # to avoid duplicate line in Test Analytics UI
-        messages = strip_invalid_utf8_chars(failure.message).split("\n")
-        messages = messages[1..-1] if index.zero?
-
-        {
-          expanded: messages,
-          backtrace: failure.backtrace
-        }
-      end
+      @failure_expanded
     end
   end
 end

lib/buildkite/test_collector/rspec_plugin/reporter.rb

@@ -16,7 +16,11 @@ def handle_example(notification)
       trace = Buildkite::TestCollector.uploader.traces[example.id]
 
       if trace
-        trace.example = example
+        trace.result = case example.execution_result.status
+                       when :passed; "passed"
+                       when :failed; "failed"
+                       when :pending; "skipped"
+                       end
         if example.execution_result.status == :failed
           trace.failure_reason, trace.failure_expanded = failure_info(notification)
         end

lib/buildkite/test_collector/rspec_plugin/trace.rb

@@ -2,56 +2,54 @@
 
 module Buildkite::TestCollector::RSpecPlugin
   class Trace < Buildkite::TestCollector::Trace
-    attr_accessor :example, :failure_reason, :failure_expanded
+    attr_accessor :failure_reason, :failure_expanded
+    attr_writer :result
     attr_reader :history
     attr_reader :tags
     attr_reader :location_prefix
 
     FILE_PATH_REGEX = /^(.*?\.(rb|feature))/
 
     def initialize(example, history:, failure_reason: nil, failure_expanded: [], tags: nil, location_prefix: nil)
-      @example = example
       @history = history
       @failure_reason = failure_reason
       @failure_expanded = failure_expanded
       @tags = tags
       @location_prefix = location_prefix
+
+      # Extract all data eagerly to allow GC of the test object
+      @scope = example.example_group.metadata[:full_description]
+      @name = example.description
+      @location = example.location
+      @id = strip_invalid_utf8_chars(example.id)
+      @shared_group_inclusion_backtrace = example.metadata[:shared_group_inclusion_backtrace]
     end
 
     def result
-      case example.execution_result.status
-      when :passed; "passed"
-      when :failed; "failed"
-      when :pending; "skipped"
-      end
+      @result
     end
 
     private
 
     def scope
-      example.example_group.metadata[:full_description]
+      @scope
     end
 
     def name
-      example.description
+      @name
     end
 
     def location
-      example.location
+      @location
     end
 
     def file_name
       @file_name ||= begin
-        identifier_file_name = strip_invalid_utf8_chars(example.id)[FILE_PATH_REGEX]
-        location_file_name = example.location[FILE_PATH_REGEX]
+        identifier_file_name = @id[FILE_PATH_REGEX]
+        location_file_name = @location[FILE_PATH_REGEX]
 
         if identifier_file_name != location_file_name
-          # If the identifier and location files are not the same, we assume
-          # that the test was run as part of a shared example. If this isn't the
-          # case, then there's something we haven't accounted for
           if shared_example?
-            # Taking the last frame in this backtrace will give us the original
-            # entry point for the shared example
             shared_example_call_location[FILE_PATH_REGEX]
           else
             "Unknown"
@@ -63,11 +61,11 @@ def file_name
     end
 
     def shared_example?
-      !example.metadata[:shared_group_inclusion_backtrace].empty?
+      !@shared_group_inclusion_backtrace.empty?
     end
 
     def shared_example_call_location
-      example.metadata[:shared_group_inclusion_backtrace].last.inclusion_location
+      @shared_group_inclusion_backtrace.last.inclusion_location
     end
   end
 end

spec/support/rspec_example_trace_helpers.rb

@@ -52,9 +52,9 @@ def fake_example(opts = {})
   end
 
   def fake_trace(a_example)
-    fake_trace = double("Buildkite::TestCollector::RSpecPlugin::Trace", example: a_example)
+    fake_trace = double("Buildkite::TestCollector::RSpecPlugin::Trace")
     allow(fake_trace).to receive(:[]) { fake_trace }
-    allow(fake_trace).to receive(:example=)
+    allow(fake_trace).to receive(:result=)
     allow(fake_trace).to receive(:failure_reason=)
     allow(fake_trace).to receive(:failure_expanded=)
     fake_trace

spec/test_collector/http_client_spec.rb

@@ -18,11 +18,16 @@
       description: "mince and cheese",
       id: "12",
       location: "123 Pie St",
-      execution_result: execution_result
+      execution_result: execution_result,
+      metadata: { shared_group_inclusion_backtrace: [] }
     )
   end
 
-  let(:trace) { Buildkite::TestCollector::RSpecPlugin::Trace.new(example, history: "pie lore") }
+  let(:trace) do
+    t = Buildkite::TestCollector::RSpecPlugin::Trace.new(example, history: "pie lore")
+    t.result = "passed"
+    t
+  end
 
   let(:http_double) { double("Net::HTTP_double") }
   let(:post_double) { double("Net::HTTP::Post") }