Avoid creating Struct at runtime

gems/aws-sdk-core/CHANGELOG.md

@@ -1,6 +1,8 @@
 Unreleased Changes
 ------------------
 
+* Feature - Seahorse::Client::Configuration no longer generate real Ruby Struct at runtime.
+
 3.265.0 (2026-11-06)
 ------------------
 

gems/aws-sdk-core/lib/seahorse/client/configuration.rb

@@ -73,6 +73,58 @@ def call(*args)
         end
       end
 
+      # @api private
+      class DynamicStruct
+        attr_reader :members
+
+        def initialize(members)
+          @members = members.map(&:to_sym).to_set
+          @attributes = {}
+        end
+
+        def [](name)
+          name = name.to_sym
+          unless @members.include?(name)
+            raise NameError, "No member #{name} in Struct"
+          end
+
+          @attributes[name]
+        end
+
+        def []=(name, value)
+          name = name.to_sym
+          unless @members.include?(name)
+            raise NameError, "No member #{name} in Struct"
+          end
+
+          @attributes[name] = value
+        end
+
+        private
+
+        alias_method :write_attribute, :[]=
+        alias_method :read_attribute, :[]
+
+        def method_missing(name, *args, **kwargs, &block)
+          if name.end_with?('=')
+            attr_name = name[0..-2].to_sym
+            if @members.include?(attr_name)
+              write_attribute(attr_name, *args, **kwargs, &block)
+            else
+              super
+            end
+          elsif @members.include?(name)
+            read_attribute(name, *args, **kwargs, &block)
+          else
+            super
+          end
+        end
+
+        def respond_to_missing?(name, include_private = false)
+          @members.include?(name) || (name.end_with?('=') && @members.include?(name[0..-2].to_sym)) || super
+        end
+      end
+
       # @api private
       def initialize
         @defaults = Hash.new { |h,k| h[k] = Defaults.new }
@@ -156,7 +208,7 @@ def build!(options = {})
       private
 
       def empty_struct
-        Struct.new(*@defaults.keys.sort).new
+        DynamicStruct.new(@defaults.keys.sort)
       end
 
       def apply_options(struct, options)

gems/aws-sdk-core/spec/seahorse/client/base_spec.rb

@@ -24,7 +24,7 @@ module Client
       describe '#config' do
 
         it 'returns a Configuration struct' do
-          expect(client.config).to be_kind_of(Struct)
+          expect(client.config).to be_kind_of(Configuration::DynamicStruct)
         end
 
         it 'contains the client api' do

gems/aws-sdk-core/spec/seahorse/client/configuration_spec.rb

@@ -66,15 +66,15 @@ module Client
         it 'returns self so it can be chained' do
           c = config.add_option(:name).add_option(:color)
           expect(c).to be(config)
-          expect(c.build!.members).to eq([:color, :name])
+          expect(c.build!.members).to eq(Set[:color, :name])
         end
 
       end
 
       describe '#build!' do
 
         it 'returns a Struct' do
-          expect(config.add_option(:opt).build!).to be_kind_of(Struct)
+          expect(config.add_option(:opt).build!).to be_kind_of(Configuration::DynamicStruct)
         end
 
         it 'accepts a hash of options' do