From d3599d8affa90b60b4e9ab24fdbd35477b5ac06d Mon Sep 17 00:00:00 2001
From: Eugene Kenny <elkenny@gmail.com>
Date: Thu, 5 Mar 2020 01:24:14 +0000
Subject: [PATCH] Use index_by and index_with wherever possible

Using `index_by` or `index_with` is more concise than `each_with_object`
and more performant than `map { ... }.to_h` or `Hash[map { ... }]`.
---
 .../partial_renderer/collection_caching.rb    | 19 ++++++++++---------
 .../test/template/form_options_helper_test.rb |  7 ++++---
 .../active_record/associations/preloader.rb   |  6 ++++--
 .../lib/active_record/attribute_methods.rb    |  5 +++--
 activerecord/lib/active_record/core.rb        |  5 ++---
 activerecord/lib/active_record/insert_all.rb  |  4 +++-
 .../active_record/relation/calculations.rb    |  4 +++-
 .../lib/active_record/test_fixtures.rb        |  5 +++--
 .../test/cases/arel/support/fake_record.rb    |  6 ++++--
 .../test/cases/attribute_methods/read_test.rb |  7 ++++---
 activerecord/test/cases/base_test.rb          |  7 ++++---
 activerecord/test/cases/counter_cache_test.rb |  5 +++--
 activesupport/lib/active_support/cache.rb     |  5 +++--
 .../active_support/cache/mem_cache_store.rb   |  3 ++-
 .../lib/active_support/current_attributes.rb  |  3 ++-
 .../lib/active_support/testing/assertions.rb  |  4 +++-
 railties/lib/rails/generators.rb              |  3 ++-
 17 files changed, 59 insertions(+), 39 deletions(-)

diff --git a/actionview/lib/action_view/renderer/partial_renderer/collection_caching.rb b/actionview/lib/action_view/renderer/partial_renderer/collection_caching.rb
index c12a25a5ec..71458185a6 100644
--- a/actionview/lib/action_view/renderer/partial_renderer/collection_caching.rb
+++ b/actionview/lib/action_view/renderer/partial_renderer/collection_caching.rb
@@ -1,5 +1,7 @@
 # frozen_string_literal: true
 
+require "active_support/core_ext/enumerable"
+
 module ActionView
   module CollectionCaching # :nodoc:
     extend ActiveSupport::Concern
@@ -88,16 +90,15 @@ module ActionView
       # If the partial is not already cached it will also be
       # written back to the underlying cache store.
       def fetch_or_cache_partial(cached_partials, template, order_by:)
-        order_by.each_with_object({}) do |cache_key, hash|
-            hash[cache_key] =
-              if content = cached_partials[cache_key]
-                build_rendered_template(content, template)
-              else
-                yield.tap do |rendered_partial|
-                  collection_cache.write(cache_key, rendered_partial.body)
-                end
-              end
+        order_by.index_with do |cache_key|
+          if content = cached_partials[cache_key]
+            build_rendered_template(content, template)
+          else
+            yield.tap do |rendered_partial|
+              collection_cache.write(cache_key, rendered_partial.body)
+            end
           end
+        end
       end
   end
 end
diff --git a/actionview/test/template/form_options_helper_test.rb b/actionview/test/template/form_options_helper_test.rb
index dc6990c4b7..403190030d 100644
--- a/actionview/test/template/form_options_helper_test.rb
+++ b/actionview/test/template/form_options_helper_test.rb
@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
 require "abstract_unit"
+require "active_support/core_ext/enumerable"
 
 class Map < Hash
   def category
@@ -67,9 +68,9 @@ class FormOptionsHelperTest < ActionView::TestCase
   ActiveSupport::TimeZone.prepend FakeZones
 
   setup do
-    ActiveSupport::TimeZone.fake_zones = %w(A B C D E).map do |id|
-      [ id, FakeZones::FakeZone.new(id) ]
-    end.to_h
+    ActiveSupport::TimeZone.fake_zones = %w(A B C D E).index_with do |id|
+      FakeZones::FakeZone.new(id)
+    end
 
     @fake_timezones = ActiveSupport::TimeZone.all
   end
diff --git a/activerecord/lib/active_record/associations/preloader.rb b/activerecord/lib/active_record/associations/preloader.rb
index 411b01bbe4..304d7d1a3a 100644
--- a/activerecord/lib/active_record/associations/preloader.rb
+++ b/activerecord/lib/active_record/associations/preloader.rb
@@ -1,5 +1,7 @@
 # frozen_string_literal: true
 
+require "active_support/core_ext/enumerable"
+
 module ActiveRecord
   module Associations
     # Implements the details of eager loading of Active Record associations.
@@ -171,8 +173,8 @@ module ActiveRecord
           end
 
           def records_by_owner
-            @records_by_owner ||= owners.each_with_object({}) do |owner, result|
-              result[owner] = Array(owner.association(reflection.name).target)
+            @records_by_owner ||= owners.index_with do |owner|
+              Array(owner.association(reflection.name).target)
             end
           end
 
diff --git a/activerecord/lib/active_record/attribute_methods.rb b/activerecord/lib/active_record/attribute_methods.rb
index 2d52ccd088..4f65385701 100644
--- a/activerecord/lib/active_record/attribute_methods.rb
+++ b/activerecord/lib/active_record/attribute_methods.rb
@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
 require "mutex_m"
+require "active_support/core_ext/enumerable"
 
 module ActiveRecord
   # = Active Record Attribute Methods
@@ -375,8 +376,8 @@ module ActiveRecord
       end
 
       def attributes_with_values(attribute_names)
-        attribute_names.each_with_object({}) do |name, attrs|
-          attrs[name] = _read_attribute(name)
+        attribute_names.index_with do |name|
+          _read_attribute(name)
         end
       end
 
diff --git a/activerecord/lib/active_record/core.rb b/activerecord/lib/active_record/core.rb
index 4e5af4ac00..f879abdd28 100644
--- a/activerecord/lib/active_record/core.rb
+++ b/activerecord/lib/active_record/core.rb
@@ -1,5 +1,6 @@
 # frozen_string_literal: true
 
+require "active_support/core_ext/enumerable"
 require "active_support/core_ext/hash/indifferent_access"
 require "active_support/core_ext/string/filters"
 require "active_support/parameter_filter"
@@ -208,9 +209,7 @@ module ActiveRecord
         keys = hash.keys
 
         statement = cached_find_by_statement(keys) { |params|
-          wheres = keys.each_with_object({}) { |param, o|
-            o[param] = params.bind
-          }
+          wheres = keys.index_with { params.bind }
           where(wheres).limit(1)
         }
         begin
diff --git a/activerecord/lib/active_record/insert_all.rb b/activerecord/lib/active_record/insert_all.rb
index c002c193b5..0a02b2e550 100644
--- a/activerecord/lib/active_record/insert_all.rb
+++ b/activerecord/lib/active_record/insert_all.rb
@@ -1,5 +1,7 @@
 # frozen_string_literal: true
 
+require "active_support/core_ext/enumerable"
+
 module ActiveRecord
   class InsertAll # :nodoc:
     attr_reader :model, :connection, :inserts, :keys
@@ -179,7 +181,7 @@ module ActiveRecord
             unknown_column = (keys - columns.keys).first
             raise UnknownAttributeError.new(model.new, unknown_column) if unknown_column
 
-            keys.map { |key| [ key, connection.lookup_cast_type_from_column(columns[key]) ] }.to_h
+            keys.index_with { |key| connection.lookup_cast_type_from_column(columns[key]) }
           end
 
           def format_columns(columns)
diff --git a/activerecord/lib/active_record/relation/calculations.rb b/activerecord/lib/active_record/relation/calculations.rb
index 23a0b563ef..d134fdb0b8 100644
--- a/activerecord/lib/active_record/relation/calculations.rb
+++ b/activerecord/lib/active_record/relation/calculations.rb
@@ -1,5 +1,7 @@
 # frozen_string_literal: true
 
+require "active_support/core_ext/enumerable"
+
 module ActiveRecord
   module Calculations
     # Count the records.
@@ -354,7 +356,7 @@ module ActiveRecord
         if association
           key_ids     = calculated_data.collect { |row| row[group_aliases.first] }
           key_records = association.klass.base_class.where(association.klass.base_class.primary_key => key_ids)
-          key_records = Hash[key_records.map { |r| [r.id, r] }]
+          key_records = key_records.index_by(&:id)
         end
 
         Hash[calculated_data.map do |row|
diff --git a/activerecord/lib/active_record/test_fixtures.rb b/activerecord/lib/active_record/test_fixtures.rb
index cdd31f7f7a..ad05c793a5 100644
--- a/activerecord/lib/active_record/test_fixtures.rb
+++ b/activerecord/lib/active_record/test_fixtures.rb
@@ -1,5 +1,7 @@
 # frozen_string_literal: true
 
+require "active_support/core_ext/enumerable"
+
 module ActiveRecord
   module TestFixtures
     extend ActiveSupport::Concern
@@ -206,8 +208,7 @@ module ActiveRecord
       end
 
       def load_fixtures(config)
-        fixtures = ActiveRecord::FixtureSet.create_fixtures(fixture_path, fixture_table_names, fixture_class_names, config)
-        Hash[fixtures.map { |f| [f.name, f] }]
+        ActiveRecord::FixtureSet.create_fixtures(fixture_path, fixture_table_names, fixture_class_names, config).index_by(&:name)
       end
 
       def instantiate_fixtures
diff --git a/activerecord/test/cases/arel/support/fake_record.rb b/activerecord/test/cases/arel/support/fake_record.rb
index 5ebeabd4a3..f03c965232 100644
--- a/activerecord/test/cases/arel/support/fake_record.rb
+++ b/activerecord/test/cases/arel/support/fake_record.rb
@@ -1,5 +1,7 @@
 # frozen_string_literal: true
 
+require "active_support/core_ext/enumerable"
+
 require "date"
 module FakeRecord
   class Column < Struct.new(:name, :type)
@@ -24,8 +26,8 @@ module FakeRecord
         ]
       }
       @columns_hash = {
-        "users" => Hash[@columns["users"].map { |x| [x.name, x] }],
-        "products" => Hash[@columns["products"].map { |x| [x.name, x] }]
+        "users" => @columns["users"].index_by(&:name),
+        "products" => @columns["products"].index_by(&:name)
       }
       @primary_keys = {
         "users" => "id",
diff --git a/activerecord/test/cases/attribute_methods/read_test.rb b/activerecord/test/cases/attribute_methods/read_test.rb
index 54512068ee..198a6a85a2 100644
--- a/activerecord/test/cases/attribute_methods/read_test.rb
+++ b/activerecord/test/cases/attribute_methods/read_test.rb
@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
 require "cases/helper"
+require "active_support/core_ext/enumerable"
 
 module ActiveRecord
   module AttributeMethods
@@ -30,9 +31,9 @@ module ActiveRecord
           end
 
           def self.columns_hash
-            Hash[attribute_names.map { |name|
-              [name, FakeColumn.new(name)]
-            }]
+            attribute_names.index_with { |name|
+              FakeColumn.new(name)
+            }
           end
         end
       end
diff --git a/activerecord/test/cases/base_test.rb b/activerecord/test/cases/base_test.rb
index b225be354c..8edca79a3f 100644
--- a/activerecord/test/cases/base_test.rb
+++ b/activerecord/test/cases/base_test.rb
@@ -27,6 +27,7 @@ require "models/bird"
 require "models/car"
 require "models/bulb"
 require "concurrent/atomic/count_down_latch"
+require "active_support/core_ext/enumerable"
 
 class FirstAbstractClass < ActiveRecord::Base
   self.abstract_class = true
@@ -732,9 +733,9 @@ class BasicsTest < ActiveRecord::TestCase
   def test_attributes
     category = Category.new(name: "Ruby")
 
-    expected_attributes = category.attribute_names.map do |attribute_name|
-      [attribute_name, category.public_send(attribute_name)]
-    end.to_h
+    expected_attributes = category.attribute_names.index_with do |attribute_name|
+      category.public_send(attribute_name)
+    end
 
     assert_instance_of Hash, category.attributes
     assert_equal expected_attributes, category.attributes
diff --git a/activerecord/test/cases/counter_cache_test.rb b/activerecord/test/cases/counter_cache_test.rb
index cc4f86a0fb..155c637aa3 100644
--- a/activerecord/test/cases/counter_cache_test.rb
+++ b/activerecord/test/cases/counter_cache_test.rb
@@ -16,6 +16,7 @@ require "models/friendship"
 require "models/subscriber"
 require "models/subscription"
 require "models/book"
+require "active_support/core_ext/enumerable"
 
 class CounterCacheTest < ActiveRecord::TestCase
   fixtures :topics, :categories, :categorizations, :cars, :dogs, :dog_lovers, :people, :friendships, :subscribers, :subscriptions, :books
@@ -355,8 +356,8 @@ class CounterCacheTest < ActiveRecord::TestCase
 
   private
     def assert_touching(record, *attributes)
-      record.update_columns attributes.map { |attr| [ attr, 5.minutes.ago ] }.to_h
-      touch_times = attributes.map { |attr| [ attr, record.public_send(attr) ] }.to_h
+      record.update_columns attributes.index_with(5.minutes.ago)
+      touch_times = attributes.index_with { |attr| record.public_send(attr) }
 
       yield
 
diff --git a/activesupport/lib/active_support/cache.rb b/activesupport/lib/active_support/cache.rb
index 7ec1a66369..bfaca88681 100644
--- a/activesupport/lib/active_support/cache.rb
+++ b/activesupport/lib/active_support/cache.rb
@@ -3,6 +3,7 @@
 require "zlib"
 require "active_support/core_ext/array/extract_options"
 require "active_support/core_ext/array/wrap"
+require "active_support/core_ext/enumerable"
 require "active_support/core_ext/module/attribute_accessors"
 require "active_support/core_ext/numeric/bytes"
 require "active_support/core_ext/numeric/time"
@@ -440,8 +441,8 @@ module ActiveSupport
         instrument :read_multi, names, options do |payload|
           reads   = read_multi_entries(names, **options)
           writes  = {}
-          ordered = names.each_with_object({}) do |name, hash|
-            hash[name] = reads.fetch(name) { writes[name] = yield(name) }
+          ordered = names.index_with do |name|
+            reads.fetch(name) { writes[name] = yield(name) }
           end
 
           payload[:hits] = reads.keys
diff --git a/activesupport/lib/active_support/cache/mem_cache_store.rb b/activesupport/lib/active_support/cache/mem_cache_store.rb
index 18a62f52d3..bebe87b019 100644
--- a/activesupport/lib/active_support/cache/mem_cache_store.rb
+++ b/activesupport/lib/active_support/cache/mem_cache_store.rb
@@ -7,6 +7,7 @@ rescue LoadError => e
   raise e
 end
 
+require "active_support/core_ext/enumerable"
 require "active_support/core_ext/marshal"
 require "active_support/core_ext/array/extract_options"
 
@@ -162,7 +163,7 @@ module ActiveSupport
 
         # Reads multiple entries from the cache implementation.
         def read_multi_entries(names, **options)
-          keys_to_names = Hash[names.map { |name| [normalize_key(name, options), name] }]
+          keys_to_names = names.index_by { |name| normalize_key(name, options) }
 
           raw_values = @data.with { |c| c.get_multi(keys_to_names.keys) }
           values = {}
diff --git a/activesupport/lib/active_support/current_attributes.rb b/activesupport/lib/active_support/current_attributes.rb
index f6eba2ba44..d2d16b2629 100644
--- a/activesupport/lib/active_support/current_attributes.rb
+++ b/activesupport/lib/active_support/current_attributes.rb
@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
 require "active_support/callbacks"
+require "active_support/core_ext/enumerable"
 
 module ActiveSupport
   # Abstract super class that provides a thread-isolated attributes singleton, which resets automatically
@@ -201,7 +202,7 @@ module ActiveSupport
       end
 
       def compute_attributes(keys)
-        keys.collect { |key| [ key, public_send(key) ] }.to_h
+        keys.index_with { |key| public_send(key) }
       end
   end
 end
diff --git a/activesupport/lib/active_support/testing/assertions.rb b/activesupport/lib/active_support/testing/assertions.rb
index 7ff9fd0532..d564cad808 100644
--- a/activesupport/lib/active_support/testing/assertions.rb
+++ b/activesupport/lib/active_support/testing/assertions.rb
@@ -1,5 +1,7 @@
 # frozen_string_literal: true
 
+require "active_support/core_ext/enumerable"
+
 module ActiveSupport
   module Testing
     module Assertions
@@ -89,7 +91,7 @@ module ActiveSupport
           else
             difference = args[0] || 1
             message = args[1]
-            Hash[Array(expression).map { |e| [e, difference] }]
+            Array(expression).index_with(difference)
           end
 
         exps = expressions.keys.map { |e|
diff --git a/railties/lib/rails/generators.rb b/railties/lib/rails/generators.rb
index df4330486b..fb328c70ef 100644
--- a/railties/lib/rails/generators.rb
+++ b/railties/lib/rails/generators.rb
@@ -8,6 +8,7 @@ require "rails/command"
 
 require "active_support/core_ext/kernel/singleton_class"
 require "active_support/core_ext/array/extract_options"
+require "active_support/core_ext/enumerable"
 require "active_support/core_ext/hash/deep_merge"
 require "active_support/core_ext/module/attribute_accessors"
 require "active_support/core_ext/string/indent"
@@ -252,7 +253,7 @@ module Rails
 
         lookup(lookups)
 
-        namespaces = Hash[subclasses.map { |klass| [klass.namespace, klass] }]
+        namespaces = subclasses.index_by(&:namespace)
         lookups.each do |namespace|
           klass = namespaces[namespace]
           return klass if klass