micro optimizations in allocating hashes and arrays

There were a few places where hashes could be mutated without side effects,
they already work with copies of original hashes. So, `merge!` replaced some
of `merge` calls.

Also, `Grape::Util::StackableValues`, `Grape::Util::ReverseStackableValues` and
`Grape::Util::InheritableValues` got a base class which keeps common methods
to avoid duplication. Besides, that a `[]` and `keys` methods were optimized
to allocate less arrays when it is possible.

There is an additional benchmark which measures more complex scenario. Unfortunately,
there isn't noticeable difference in performance between the master and this change.
However, I also profiled the same endpoint as the benchmark has.

Before this change:

     Measure Mode: memory
     Thread ID: 47216803207600
     Fiber ID: 47216805628400
     Total: 40536.000000
     Sort by: self_time

     %self      total      self      wait     child     calls  name
     13.85   6848.000  5616.000     0.000  1232.000       15  *Hash#each_pair
     9.73    3944.000  3944.000     0.000     0.000       17   Hash#merge
     8.80    5088.000  3568.000     0.000  1520.000        8  *Array#map
     8.57   11720.000  3472.000     0.000  8248.000       27  *Class#new
     4.54    1840.000  1840.000     0.000     0.000       46   Symbol#to_s
     4.44    1800.000  1800.000     0.000     0.000       20  *Grape::Util::StackableValues#[]
     3.36    1440.000  1360.000     0.000    80.000        5   Grape::Endpoint#run_filters
     2.88    3040.000  1168.000     0.000  1872.000        9  *Hash#each
     2.37    1200.000   960.000     0.000   240.000        6   <Class::Grape::Router>#normalize_path
     2.29    1088.000   928.000     0.000   160.000        4   ActiveSupport::HashWithIndifferentAccess#[]=
     2.21    1128.000   896.000     0.000   232.000        8  *Kernel#dup
     2.07     840.000   840.000     0.000     0.000        9   String#split
     1.64   12008.000   664.000     0.000 11344.000        1   Grape::Endpoint#run_validators

After this change:

     Measure Mode: memory
     Thread ID: 47390769740200
     Fiber ID: 47390772121400
     Total: 37296.000000
     Sort by: self_time

     %self      total      self      wait     child     calls  name
     15.06   6848.000  5616.000     0.000  1232.000       15  *Hash#each_pair
     9.57    5088.000  3568.000     0.000  1520.000        8  *Array#map
     9.31   11720.000  3472.000     0.000  8248.000       27  *Class#new
     4.93    1840.000  1840.000     0.000     0.000       46   Symbol#to_s
     4.35    1624.000  1624.000     0.000     0.000        7   Hash#merge
     3.65    1440.000  1360.000     0.000    80.000        5   Grape::Endpoint#run_filters
     3.13    3040.000  1168.000     0.000  1872.000        9  *Hash#each
     2.57    1200.000   960.000     0.000   240.000        6   <Class::Grape::Router>#normalize_path
     2.49    1088.000   928.000     0.000   160.000        4   ActiveSupport::HashWithIndifferentAccess#[]=
     2.40    1128.000   896.000     0.000   232.000        8  *Kernel#dup
     2.25     840.000   840.000     0.000     0.000        9   String#split
     2.15    1400.000   800.000     0.000   600.000       20  *Grape::Util::StackableValues#[]
     1.78   11768.000   664.000     0.000 11104.000        1   Grape::Endpoint#run_validators

 - The total memory usage went down from 40536 to 37296 bytes.
 - `Hash#merge` moved from second position to 5th.
 - `Grape::Util::StackableValues#[]` moved from 6th to 12th.

CHANGELOG.md

@@ -3,6 +3,7 @@
 #### Features
 
 * Your contribution here.
+* [#1915](https://github.com/ruby-grape/grape/pull/1915): Micro optimizations in allocating hashes and arrays - [@dnesteryuk](https://github.com/dnesteryuk).
 * [#1904](https://github.com/ruby-grape/grape/pull/1904): Allows Grape to load files on startup rather than on the first call - [@myxoh](https://github.com/myxoh).
 * [#1907](https://github.com/ruby-grape/grape/pull/1907): Adds outside configuration to Grape with `configure` - [@unleashy](https://github.com/unleashy).
 

benchmark/nested_params.rb

@@ -0,0 +1,41 @@
+require 'grape'
+require 'benchmark/ips'
+
+class API < Grape::API
+  prefix :api
+  version 'v1', using: :path
+
+  params do
+    requires :address, type: Hash do
+      requires :street, type: String
+      requires :postal_code, type: Integer
+      optional :city, type: String
+    end
+  end
+  post '/' do
+    'hello'
+  end
+end
+
+options = {
+  method: 'POST',
+  params: {
+    address: {
+      street: 'Alexis Pl.',
+      postal_code: '90210',
+      city: 'Beverly Hills'
+    }
+  }
+}
+
+env = Rack::MockRequest.env_for('/api/v1', options)
+
+10.times do |i|
+  env["HTTP_HEADER#{i}"] = '123'
+end
+
+Benchmark.ips do |ips|
+  ips.report('POST with nested params') do
+    API.call env
+  end
+end

lib/grape/endpoint.rb

@@ -200,7 +200,7 @@ def prepare_version
     end
 
     def merge_route_options(**default)
-      options[:route_options].clone.merge(**default)
+      options[:route_options].clone.merge!(**default)
     end
 
     def map_routes

lib/grape/error_formatter.rb

@@ -14,7 +14,7 @@ def builtin_formatters
       end
 
       def formatters(options)
-        builtin_formatters.merge(default_elements).merge(options[:error_formatters] || {})
+        builtin_formatters.merge(default_elements).merge!(options[:error_formatters] || {})
       end
 
       def formatter_for(api_format, **options)

lib/grape/exceptions/validation_errors.rb

@@ -39,14 +39,16 @@ def to_json(**_opts)
       end
 
       def full_messages
-        map { |attributes, error| full_message(attributes, error) }.uniq
+        messages = map { |attributes, error| full_message(attributes, error) }
+        messages.uniq!
+        messages
       end
 
       private
 
       def full_message(attributes, error)
         I18n.t(
-          'grape.errors.format'.to_sym,
+          'grape.errors.format',
           default: '%{attributes} %{message}',
           attributes: attributes.count == 1 ? translate_attribute(attributes.first) : translate_attributes(attributes),
           message: error.message

lib/grape/formatter.rb

@@ -14,7 +14,7 @@ def builtin_formmaters
       end
 
       def formatters(options)
-        builtin_formmaters.merge(default_elements).merge(options[:formatters] || {})
+        builtin_formmaters.merge(default_elements).merge!(options[:formatters] || {})
       end
 
       def formatter_for(api_format, **options)

lib/grape/parser.rb

@@ -12,7 +12,7 @@ def builtin_parsers
       end
 
       def parsers(options)
-        builtin_parsers.merge(default_elements).merge(options[:parsers] || {})
+        builtin_parsers.merge(default_elements).merge!(options[:parsers] || {})
       end
 
       def parser_for(api_format, **options)

lib/grape/util/base_inheritable.rb

@@ -0,0 +1,34 @@
+module Grape
+  module Util
+    # Base for classes which need to operate with own values kept
+    # in the hash and inherited values kept in a Hash-like object.
+    class BaseInheritable
+      attr_accessor :inherited_values
+      attr_accessor :new_values
+
+      # @param inherited_values [Object] An object implementing an interface
+      #   of the Hash class.
+      def initialize(inherited_values = {})
+        @inherited_values = inherited_values
+        @new_values = {}
+      end
+
+      def delete(key)
+        new_values.delete key
+      end
+
+      def initialize_copy(other)
+        super
+        self.inherited_values = other.inherited_values
+        self.new_values = other.new_values.dup
+      end
+
+      def keys
+        combined = inherited_values.keys
+        combined.concat(new_values.keys)
+        combined.uniq!
+        combined
+      end
+    end
+  end
+end

lib/grape/util/inheritable_values.rb

@@ -1,14 +1,8 @@
+require_relative 'base_inheritable'
+
 module Grape
   module Util
-    class InheritableValues
-      attr_accessor :inherited_values
-      attr_accessor :new_values
-
-      def initialize(inherited_values = {})
-        self.inherited_values = inherited_values
-        self.new_values = {}
-      end
-
+    class InheritableValues < BaseInheritable
       def [](name)
         values[name]
       end
@@ -17,26 +11,12 @@ def []=(name, value)
         new_values[name] = value
       end
 
-      def delete(key)
-        new_values.delete key
-      end
-
       def merge(new_hash)
-        values.merge(new_hash)
-      end
-
-      def keys
-        (new_values.keys + inherited_values.keys).sort.uniq
+        values.merge!(new_hash)
       end
 
       def to_hash
-        values.clone
-      end
-
-      def initialize_copy(other)
-        super
-        self.inherited_values = other.inherited_values
-        self.new_values = other.new_values.dup
+        values
       end
 
       protected

lib/grape/util/reverse_stackable_values.rb

@@ -1,45 +1,16 @@
+require_relative 'stackable_values'
+
 module Grape
   module Util
-    class ReverseStackableValues
-      attr_accessor :inherited_values
-      attr_accessor :new_values
-
-      def initialize(inherited_values = {})
-        @inherited_values = inherited_values
-        @new_values = {}
-      end
+    class ReverseStackableValues < StackableValues
+      protected
 
-      def [](name)
+      def concat_values(inherited_value, new_value)
         [].tap do |value|
-          value.concat(@new_values[name] || [])
-          value.concat(@inherited_values[name] || [])
-        end
-      end
-
-      def []=(name, value)
-        @new_values[name] ||= []
-        @new_values[name].push value
-      end
-
-      def delete(key)
-        new_values.delete key
-      end
-
-      def keys
-        (@new_values.keys + @inherited_values.keys).sort.uniq
-      end
-
-      def to_hash
-        keys.each_with_object({}) do |key, result|
-          result[key] = self[key]
+          value.concat(new_value)
+          value.concat(inherited_value)
         end
       end
-
-      def initialize_copy(other)
-        super
-        self.inherited_values = other.inherited_values
-        self.new_values = other.new_values.dup
-      end
     end
   end
 end

lib/grape/util/stackable_values.rb

@@ -1,23 +1,25 @@
+require_relative 'base_inheritable'
+
 module Grape
   module Util
-    class StackableValues
-      attr_accessor :inherited_values
-      attr_accessor :new_values
+    class StackableValues < BaseInheritable
       attr_reader :frozen_values
 
-      def initialize(inherited_values = {})
-        @inherited_values = inherited_values
-        @new_values = {}
+      def initialize(*_args)
+        super
+
         @frozen_values = {}
       end
 
       def [](name)
         return @frozen_values[name] if @frozen_values.key? name
 
-        value = []
-        value.concat(@inherited_values[name] || [])
-        value.concat(@new_values[name] || [])
-        value
+        inherited_value = @inherited_values[name]
+        new_value = @new_values[name] || []
+
+        return new_value unless inherited_value
+
+        concat_values(inherited_value, new_value)
       end
 
       def []=(name, value)
@@ -26,14 +28,6 @@ def []=(name, value)
         @new_values[name].push value
       end
 
-      def delete(key)
-        new_values.delete key
-      end
-
-      def keys
-        (@new_values.keys + @inherited_values.keys).sort.uniq
-      end
-
       def to_hash
         keys.each_with_object({}) do |key, result|
           result[key] = self[key]
@@ -44,10 +38,13 @@ def freeze_value(key)
         @frozen_values[key] = self[key].freeze
       end
 
-      def initialize_copy(other)
-        super
-        self.inherited_values = other.inherited_values
-        self.new_values = other.new_values.dup
+      protected
+
+      def concat_values(inherited_value, new_value)
+        [].tap do |value|
+          value.concat(inherited_value)
+          value.concat(new_value)
+        end
       end
     end
   end

lib/grape/validations/validators/base.rb

@@ -56,10 +56,10 @@ def validate!(params)
 
       def self.convert_to_short_name(klass)
         ret = klass.name.gsub(/::/, '/')
-                   .gsub(/([A-Z]+)([A-Z][a-z])/, '\1_\2')
-                   .gsub(/([a-z\d])([A-Z])/, '\1_\2')
-                   .tr('-', '_')
-                   .downcase
+        ret.gsub!(/([A-Z]+)([A-Z][a-z])/, '\1_\2')
+        ret.gsub!(/([a-z\d])([A-Z])/, '\1_\2')
+        ret.tr!('-', '_')
+        ret.downcase!
         File.basename(ret, '_validator')
       end