Fix adapter field for AMS logs

Author: ndbroadbent

lib/log_struct/integrations/active_model_serializers.rb

@@ -31,8 +31,8 @@ def self.setup(config)
           LogStruct.info(
             LogStruct::Log::ActiveModelSerializers.new(
               message: "ams.render",
-              serializer: serializer&.to_s,
-              adapter: adapter&.to_s,
+              serializer: serializer&.name,
+              adapter: adapter&.class&.name,
               resource_class: resource&.class&.name,
               duration_ms: duration_ms,
               timestamp: started

rails_test_app/templates/app/controllers/logging_controller.rb

@@ -145,6 +145,12 @@ def test_error_logging
     render json: {status: "ok", message: "Stack-safe error handling test completed"}
   end
 
+  # AMS serialization - triggers ActiveModelSerializers instrumentation
+  def test_ams_serialization
+    user = User.create!(name: "AMS Test User", email: "ams@example.com")
+    render json: user, serializer: UserSerializer
+  end
+
   # Shrine file upload - triggers Shrine instrumentation logging
   def test_shrine_upload
     document = Document.create_with_shrine_file(

rails_test_app/templates/app/serializers/user_serializer.rb

@@ -0,0 +1,6 @@
+# typed: true
+# frozen_string_literal: true
+
+class UserSerializer < ActiveModel::Serializer
+  attributes :id, :name, :email
+end

rails_test_app/templates/config/routes.rb

@@ -12,6 +12,7 @@
   get "/logging/request", to: "logging#test_request"
   get "/logging/error_logging", to: "logging#test_error_logging"
   get "/logging/shrine_upload", to: "logging#test_shrine_upload"
+  get "/logging/ams", to: "logging#test_ams_serialization"
 
   # Healthcheck route
   get "/health", to: proc { [200, {}, ["OK"]] }

rails_test_app/templates/test/integration/ams_logging_test.rb

@@ -76,4 +76,40 @@ def test_ams_logs_do_not_pollute_with_default_format
       stdout_output,
       "AMS default log format should not appear in stdout")
   end
+
+  def test_ams_logs_adapter_class_name_not_serialized_output
+    raise "AMS not available" unless defined?(::ActiveModelSerializers)
+
+    get "/logging/ams"
+
+    ::SemanticLogger.flush
+    @log_output.rewind
+    output = @log_output.read.to_s
+
+    # Find the AMS log line
+    ams_lines = output.lines.select { |line| line.include?('"msg":"ams.render"') }
+
+    assert_predicate ams_lines, :any?, "Expected to find ams.render log line, got:\n#{output}"
+
+    ams_line = ams_lines.first
+    parsed = JSON.parse(ams_line)
+
+    # serializer should be the class name
+    assert_equal "UserSerializer",
+      parsed["serializer"],
+      "Expected serializer to be 'UserSerializer', got: #{parsed["serializer"]}"
+
+    # adapter should be the adapter CLASS NAME, not serialized output
+    adapter = parsed["adapter"]
+
+    assert_kind_of String, adapter, "adapter should be a string"
+    assert_match(/^ActiveModelSerializers::Adapter::/,
+      adapter,
+      "adapter should be an AMS adapter class name like 'ActiveModelSerializers::Adapter::Attributes', got: #{adapter.inspect}")
+
+    # MUST NOT contain serialized user data (the bug we're fixing)
+    refute_includes adapter,
+      "AMS Test User",
+      "adapter field MUST NOT contain serialized output"
+  end
 end

test/log_struct/integrations/active_model_serializers_test.rb

@@ -22,17 +22,25 @@ class ActiveModelSerializersTest < ActiveSupport::TestCase
       test "subscribes to AMS notifications and emits structured log" do
         logs = []
         LogStruct.stub(:info, ->(log) { logs << log }) do
-          serializer = Class.new do
-            def self.to_s
+          serializer_class = Class.new do
+            def self.name
               "UserSerializer"
             end
           end
+
+          adapter_class = Class.new do
+            def self.name
+              "ActiveModelSerializers::Adapter::Json"
+            end
+          end
+          adapter_instance = adapter_class.new
+
           resource = OpenStruct.new(id: 1)
 
           ActiveSupport::Notifications.instrument(
             "render.active_model_serializers",
-            serializer: serializer,
-            adapter: :json,
+            serializer: serializer_class,
+            adapter: adapter_instance,
             resource: resource
           ) { sleep 0.001 }
         end
@@ -47,7 +55,7 @@ def self.to_s
         assert_equal "generate", json["evt"]
         assert_equal "ams.render", json["msg"]
         assert_equal "UserSerializer", json["serializer"]
-        assert_equal "json", json["adapter"]
+        assert_equal "ActiveModelSerializers::Adapter::Json", json["adapter"]
         assert_equal "OpenStruct", json["resource_class"]
         assert_in_delta 0.0, json["duration_ms"], 50.0
       end