Improve attribute methods generation

CHANGELOG.md

@@ -2,6 +2,9 @@
 
 ### [0-9-stable](https://github.com/rails-api/active_model_serializers/compare/v0.9.12...0-9-stable)
 
+- Perf
+  - [#2471](https://github.com/rails-api/active_model_serializers/pull/2471) Generate better attribute accessors, that also don't trigger warnings when redefined. (@byroot)
+
 ### [v0.9.12 (2024-04-11)](https://github.com/rails-api/active_model_serializers/compare/v0.9.11...v0.9.12)
 
 - Fix

Gemfile

@@ -72,8 +72,10 @@ group :test do
   platforms(*(@windows_platforms + [:ruby])) do
     if RUBY_VERSION < '2.5' || version < '6'
       gem 'sqlite3', '~> 1.3.13'
+    elsif version >= '8'
+      gem 'sqlite3', '>= 2'
     else
-      gem 'sqlite3'
+      gem 'sqlite3', '< 2'
     end
   end
   platforms :jruby do

lib/active_model/serializer.rb

@@ -90,15 +90,27 @@ def root_name
       end
 
       def attributes(*attrs)
+        # Use `class_eval` rather than `define_method` for faster access
+        # and avoid retaining objects in the closure.
+        # Batch all methods in a single `class_eval` for efficiceny,
+        # and define all methods on the same line so the eventual backtrace
+        # properly maps to the `attributes` call.
+        source = ["# frozen_string_literal: true\n"]
         attrs.each do |attr|
           striped_attr = strip_attribute attr
 
           @_attributes << striped_attr
 
-          define_method striped_attr do
-            object.read_attribute_for_serialization attr
-          end unless method_defined?(attr)
+          unless method_defined?(attr)
+            source <<
+            "def #{striped_attr}" <<
+              "object.read_attribute_for_serialization(#{attr.inspect})" <<
+            "end" <<
+            "alias_method :#{striped_attr}, :#{striped_attr}" # suppress method redefinition warning
+          end
         end
+        caller = caller_locations(1, 1).first
+        class_eval(source.join(";"), caller.path, caller.lineno - 1)
       end
 
       def has_one(*attrs)