Use native `Array#append`, `Array#prepend`, `Hash#transform_keys`, and `Hash#transform_keys!`

Since Rails 6 requires Ruby 2.5.

https://github.com/ruby/ruby/blob/ruby_2_5/NEWS

Follow up #34754.

11 files changed, 6 insertions, 181 deletions

diff --git a/actionpack/lib/action_controller/metal/conditional_get.rb b/actionpack/lib/action_controller/metal/conditional_get.rb
index d6911ee2b5..29d1919ec5 100644
--- a/actionpack/lib/action_controller/metal/conditional_get.rb
+++ b/actionpack/lib/action_controller/metal/conditional_get.rb
@@ -1,7 +1,5 @@
 # frozen_string_literal: true
 
-require "active_support/core_ext/hash/keys"
-
 module ActionController
   module ConditionalGet
     extend ActiveSupport::Concern
diff --git a/actionpack/lib/action_controller/renderer.rb b/actionpack/lib/action_controller/renderer.rb
index 2b4559c760..cf8c0159e2 100644
--- a/actionpack/lib/action_controller/renderer.rb
+++ b/actionpack/lib/action_controller/renderer.rb
@@ -1,7 +1,5 @@
 # frozen_string_literal: true
 
-require "active_support/core_ext/hash/keys"
-
 module ActionController
   # ActionController::Renderer allows you to render arbitrary templates
   # without requirement of being in controller actions.
diff --git a/activejob/lib/active_job/test_helper.rb b/activejob/lib/active_job/test_helper.rb
index e0a71f4da8..f03780b91e 100644
--- a/activejob/lib/active_job/test_helper.rb
+++ b/activejob/lib/active_job/test_helper.rb
@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "active_support/core_ext/class/subclasses"
-require "active_support/core_ext/hash/keys"
 
 module ActiveJob
   # Provides helper methods for testing Active Job
diff --git a/activemodel/lib/active_model/validations.rb b/activemodel/lib/active_model/validations.rb
index 7f14d102dd..f18f9a601a 100644
--- a/activemodel/lib/active_model/validations.rb
+++ b/activemodel/lib/active_model/validations.rb
@@ -1,8 +1,6 @@
 # frozen_string_literal: true
 
 require "active_support/core_ext/array/extract_options"
-require "active_support/core_ext/hash/keys"
-require "active_support/core_ext/hash/except"
 
 module ActiveModel
   # == Active \Model \Validations
diff --git a/activesupport/lib/active_support/core_ext/array.rb b/activesupport/lib/active_support/core_ext/array.rb
index a2569c798b..88b6567712 100644
--- a/activesupport/lib/active_support/core_ext/array.rb
+++ b/activesupport/lib/active_support/core_ext/array.rb
@@ -6,5 +6,4 @@ require "active_support/core_ext/array/conversions"
 require "active_support/core_ext/array/extract"
 require "active_support/core_ext/array/extract_options"
 require "active_support/core_ext/array/grouping"
-require "active_support/core_ext/array/prepend_and_append"
 require "active_support/core_ext/array/inquiry"
diff --git a/activesupport/lib/active_support/core_ext/array/prepend_and_append.rb b/activesupport/lib/active_support/core_ext/array/prepend_and_append.rb
index 661971d7cd..ba3739f640 100644
--- a/activesupport/lib/active_support/core_ext/array/prepend_and_append.rb
+++ b/activesupport/lib/active_support/core_ext/array/prepend_and_append.rb
@@ -1,9 +1,5 @@
 # frozen_string_literal: true
 
-class Array
-  # The human way of thinking about adding stuff to the end of a list is with append.
-  alias_method :append,  :push unless [].respond_to?(:append)
+require "active_support/deprecation"
 
-  # The human way of thinking about adding stuff to the beginning of a list is with prepend.
-  alias_method :prepend, :unshift unless [].respond_to?(:prepend)
-end
+ActiveSupport::Deprecation.warn "Ruby 2.5+ (required by Rails 6) provides Array#append and Array#prepend natively, so requiring active_support/core_ext/array/prepend_and_append is no longer necessary. Requiring it will raise LoadError in Rails 6.1."
diff --git a/activesupport/lib/active_support/core_ext/hash/keys.rb b/activesupport/lib/active_support/core_ext/hash/keys.rb
index bdf196ec3d..7d3495db2c 100644
--- a/activesupport/lib/active_support/core_ext/hash/keys.rb
+++ b/activesupport/lib/active_support/core_ext/hash/keys.rb
@@ -1,35 +1,6 @@
 # frozen_string_literal: true
 
 class Hash
-  # Returns a new hash with all keys converted using the +block+ operation.
-  #
-  #  hash = { name: 'Rob', age: '28' }
-  #
-  #  hash.transform_keys { |key| key.to_s.upcase } # => {"NAME"=>"Rob", "AGE"=>"28"}
-  #
-  # If you do not provide a +block+, it will return an Enumerator
-  # for chaining with other methods:
-  #
-  #  hash.transform_keys.with_index { |k, i| [k, i].join } # => {"name0"=>"Rob", "age1"=>"28"}
-  def transform_keys
-    return enum_for(:transform_keys) { size } unless block_given?
-    result = {}
-    each_key do |key|
-      result[yield(key)] = self[key]
-    end
-    result
-  end unless method_defined? :transform_keys
-
-  # Destructively converts all keys using the +block+ operations.
-  # Same as +transform_keys+ but modifies +self+.
-  def transform_keys!
-    return enum_for(:transform_keys!) { size } unless block_given?
-    keys.each do |key|
-      self[yield(key)] = delete(key)
-    end
-    self
-  end unless method_defined? :transform_keys!
-
   # Returns a new hash with all keys converted to strings.
   #
   #   hash = { name: 'Rob', age: '28' }
diff --git a/activesupport/lib/active_support/inflector/inflections.rb b/activesupport/lib/active_support/inflector/inflections.rb
index 2b86d233e5..fa087c4dd6 100644
--- a/activesupport/lib/active_support/inflector/inflections.rb
+++ b/activesupport/lib/active_support/inflector/inflections.rb
@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "concurrent/map"
-require "active_support/core_ext/array/prepend_and_append"
 require "active_support/i18n"
 require "active_support/deprecation"
 
diff --git a/activesupport/test/core_ext/array/prepend_append_test.rb b/activesupport/test/core_ext/array/prepend_append_test.rb
index c34acd66ad..8573dbd5a6 100644
--- a/activesupport/test/core_ext/array/prepend_append_test.rb
+++ b/activesupport/test/core_ext/array/prepend_append_test.rb
@@ -1,14 +1,11 @@
 # frozen_string_literal: true
 
 require "abstract_unit"
-require "active_support/core_ext/array"
 
 class PrependAppendTest < ActiveSupport::TestCase
-  def test_append
-    assert_equal [1, 2], [1].append(2)
-  end
-
-  def test_prepend
-    assert_equal [2, 1], [1].prepend(2)
+  def test_requiring_prepend_and_append_is_deprecated
+    assert_deprecated do
+      require "active_support/core_ext/array/prepend_and_append"
+    end
   end
 end
diff --git a/activesupport/test/core_ext/hash/transform_keys_test.rb b/activesupport/test/core_ext/hash/transform_keys_test.rb
deleted file mode 100644
index b9e41f7b25..0000000000
--- a/activesupport/test/core_ext/hash/transform_keys_test.rb
+++ /dev/null
@@ -1,64 +0,0 @@
-# frozen_string_literal: true
-
-require "abstract_unit"
-require "active_support/core_ext/hash/keys"
-
-class TransformKeysTest < ActiveSupport::TestCase
-  test "transform_keys returns a new hash with the keys computed from the block" do
-    original = { a: "a", b: "b" }
-    mapped = original.transform_keys { |k| "#{k}!".to_sym }
-
-    assert_equal({ a: "a", b: "b" }, original)
-    assert_equal({ a!: "a", b!: "b" }, mapped)
-  end
-
-  test "transform_keys! modifies the keys of the original" do
-    original = { a: "a", b: "b" }
-    mapped = original.transform_keys! { |k| "#{k}!".to_sym }
-
-    assert_equal({ a!: "a", b!: "b" }, original)
-    assert_same original, mapped
-  end
-
-  test "transform_keys returns a sized Enumerator if no block is given" do
-    original = { a: "a", b: "b" }
-    enumerator = original.transform_keys
-    assert_equal original.size, enumerator.size
-    assert_equal Enumerator, enumerator.class
-  end
-
-  test "transform_keys! returns a sized Enumerator if no block is given" do
-    original = { a: "a", b: "b" }
-    enumerator = original.transform_keys!
-    assert_equal original.size, enumerator.size
-    assert_equal Enumerator, enumerator.class
-  end
-
-  test "transform_keys is chainable with Enumerable methods" do
-    original = { a: "a", b: "b" }
-    mapped = original.transform_keys.with_index { |k, i| [k, i].join.to_sym }
-    assert_equal({ a0: "a", b1: "b" }, mapped)
-  end
-
-  test "transform_keys! is chainable with Enumerable methods" do
-    original = { a: "a", b: "b" }
-    original.transform_keys!.with_index { |k, i| [k, i].join.to_sym }
-    assert_equal({ a0: "a", b1: "b" }, original)
-  end
-
-  test "transform_keys returns a Hash instance when self is inherited from Hash" do
-    class HashDescendant < ::Hash
-      def initialize(elements = nil)
-        super(elements)
-        (elements || {}).each_pair { |key, value| self[key] = value }
-      end
-    end
-
-    original = HashDescendant.new(a: "a", b: "b")
-    mapped = original.transform_keys { |k| "#{k}!".to_sym }
-
-    assert_equal({ a: "a", b: "b" }, original)
-    assert_equal({ a!: "a", b!: "b" }, mapped)
-    assert_equal(::Hash, mapped.class)
-  end
-end
diff --git a/guides/source/active_support_core_extensions.md b/guides/source/active_support_core_extensions.md
index 6b0554bb5f..428271d9b7 100644
--- a/guides/source/active_support_core_extensions.md
+++ b/guides/source/active_support_core_extensions.md
@@ -2132,30 +2132,6 @@ The methods `second`, `third`, `fourth`, and `fifth` return the corresponding el
 
 NOTE: Defined in `active_support/core_ext/array/access.rb`.
 
-### Adding Elements
-
-#### `prepend`
-
-This method is an alias of `Array#unshift`.
-
-```ruby
-%w(a b c d).prepend('e')  # => ["e", "a", "b", "c", "d"]
-[].prepend(10)            # => [10]
-```
-
-NOTE: Defined in `active_support/core_ext/array/prepend_and_append.rb`.
-
-#### `append`
-
-This method is an alias of `Array#<<`.
-
-```ruby
-%w(a b c d).append('e')  # => ["a", "b", "c", "d", "e"]
-[].append([1,2])         # => [[1, 2]]
-```
-
-NOTE: Defined in `active_support/core_ext/array/prepend_and_append.rb`.
-
 ### Extracting
 
 The method `extract!` removes and returns the elements for which the block returns a true value.
@@ -2646,48 +2622,6 @@ There's also the bang variant `except!` that removes keys in the very receiver.
 
 NOTE: Defined in `active_support/core_ext/hash/except.rb`.
 
-#### `transform_keys` and `transform_keys!`
-
-The method `transform_keys` accepts a block and returns a hash that has applied the block operations to each of the keys in the receiver:
-
-```ruby
-{nil => nil, 1 => 1, a: :a}.transform_keys { |key| key.to_s.upcase }
-# => {"" => nil, "1" => 1, "A" => :a}
-```
-
-In case of key collision, one of the values will be chosen. The chosen value may not always be the same given the same hash:
-
-```ruby
-{"a" => 1, a: 2}.transform_keys { |key| key.to_s.upcase }
-# The result could either be
-# => {"A"=>2}
-# or
-# => {"A"=>1}
-```
-
-This method may be useful for example to build specialized conversions. For instance `stringify_keys` and `symbolize_keys` use `transform_keys` to perform their key conversions:
-
-```ruby
-def stringify_keys
-  transform_keys { |key| key.to_s }
-end
-...
-def symbolize_keys
-  transform_keys { |key| key.to_sym rescue key }
-end
-```
-
-There's also the bang variant `transform_keys!` that applies the block operations to keys in the very receiver.
-
-Besides that, one can use `deep_transform_keys` and `deep_transform_keys!` to perform the block operation on all the keys in the given hash and all the hashes nested into it. An example of the result is:
-
-```ruby
-{nil => nil, 1 => 1, nested: {a: 3, 5 => 5}}.deep_transform_keys { |key| key.to_s.upcase }
-# => {""=>nil, "1"=>1, "NESTED"=>{"A"=>3, "5"=>5}}
-```
-
-NOTE: Defined in `active_support/core_ext/hash/keys.rb`.
-
 #### `stringify_keys` and `stringify_keys!`
 
 The method `stringify_keys` returns a hash that has a stringified version of the keys in the receiver. It does so by sending `to_s` to them: