Rails 6 requires Ruby 2.4.1+

Skipping over 2.4.0 to sidestep the `"symbol_from_string".to_sym.dup` bug.

References #32028

16 files changed, 32 insertions, 141 deletions

diff --git a/activesupport/CHANGELOG.md b/activesupport/CHANGELOG.md
index 2976040a59..33d2793ffc 100644
--- a/activesupport/CHANGELOG.md
+++ b/activesupport/CHANGELOG.md
@@ -1,7 +1,14 @@
-* Adds parallel testing to Rails
+## Rails 6.0.0.alpha (Unreleased) ##
 
-  Parallelize your test suite with forked processes or threads.
+*   Rails 6 requires Ruby 2.4.1 or newer.
+
+    *Jeremy Daer*
+
+*   Adds parallel testing to Rails
+
+    Parallelize your test suite with forked processes or threads.
+
+    *Eileen M. Uchitelle*, *Aaron Patterson*
 
-  *Eileen M. Uchitelle*, *Aaron Patterson*
 
 Please check [5-2-stable](https://github.com/rails/rails/blob/5-2-stable/activesupport/CHANGELOG.md) for previous changes.
diff --git a/activesupport/activesupport.gemspec b/activesupport/activesupport.gemspec
index ee3228e677..aa695c98b2 100644
--- a/activesupport/activesupport.gemspec
+++ b/activesupport/activesupport.gemspec
@@ -9,7 +9,7 @@ Gem::Specification.new do |s|
   s.summary     = "A toolkit of support libraries and Ruby core extensions extracted from the Rails framework."
   s.description = "A toolkit of support libraries and Ruby core extensions extracted from the Rails framework. Rich support for multibyte strings, internationalization, time zones, and testing."
 
-  s.required_ruby_version = ">= 2.3.0"
+  s.required_ruby_version = ">= 2.4.1"
 
   s.license = "MIT"
 
diff --git a/activesupport/lib/active_support/cache/redis_cache_store.rb b/activesupport/lib/active_support/cache/redis_cache_store.rb
index c5f8c876ba..64bc77cf22 100644
--- a/activesupport/lib/active_support/cache/redis_cache_store.rb
+++ b/activesupport/lib/active_support/cache/redis_cache_store.rb
@@ -17,7 +17,6 @@ end
 
 require "digest/sha2"
 require "active_support/core_ext/marshal"
-require "active_support/core_ext/hash/transform_values"
 
 module ActiveSupport
   module Cache
diff --git a/activesupport/lib/active_support/core_ext/hash.rb b/activesupport/lib/active_support/core_ext/hash.rb
index e19aeaa983..325581a60a 100644
--- a/activesupport/lib/active_support/core_ext/hash.rb
+++ b/activesupport/lib/active_support/core_ext/hash.rb
@@ -8,4 +8,3 @@ require "active_support/core_ext/hash/indifferent_access"
 require "active_support/core_ext/hash/keys"
 require "active_support/core_ext/hash/reverse_merge"
 require "active_support/core_ext/hash/slice"
-require "active_support/core_ext/hash/transform_values"
diff --git a/activesupport/lib/active_support/core_ext/hash/transform_values.rb b/activesupport/lib/active_support/core_ext/hash/transform_values.rb
index 4b19c9fc1f..fc15130c9e 100644
--- a/activesupport/lib/active_support/core_ext/hash/transform_values.rb
+++ b/activesupport/lib/active_support/core_ext/hash/transform_values.rb
@@ -1,32 +1,5 @@
 # frozen_string_literal: true
 
-class Hash
-  # Returns a new hash with the results of running +block+ once for every value.
-  # The keys are unchanged.
-  #
-  #   { a: 1, b: 2, c: 3 }.transform_values { |x| x * 2 } # => { a: 2, b: 4, c: 6 }
-  #
-  # If you do not provide a +block+, it will return an Enumerator
-  # for chaining with other methods:
-  #
-  #   { a: 1, b: 2 }.transform_values.with_index { |v, i| [v, i].join.to_i } # => { a: 10, b: 21 }
-  def transform_values
-    return enum_for(:transform_values) { size } unless block_given?
-    return {} if empty?
-    result = self.class.new
-    each do |key, value|
-      result[key] = yield(value)
-    end
-    result
-  end unless method_defined? :transform_values
+require "active_support/deprecation"
 
-  # Destructively converts all values using the +block+ operations.
-  # Same as +transform_values+ but modifies +self+.
-  def transform_values!
-    return enum_for(:transform_values!) { size } unless block_given?
-    each do |key, value|
-      self[key] = yield(value)
-    end
-  end unless method_defined? :transform_values!
-  # TODO: Remove this file when supporting only Ruby 2.4+.
-end
+ActiveSupport::Deprecation.warn "Ruby 2.4+ (required by Rails 6) provides Hash#transform_values natively, so requiring active_support/core_ext/hash/transform_values is no longer necessary. Requiring it will raise LoadError in Rails 6.1."
diff --git a/activesupport/lib/active_support/core_ext/numeric/conversions.rb b/activesupport/lib/active_support/core_ext/numeric/conversions.rb
index f6c2713986..7fcd0d0311 100644
--- a/activesupport/lib/active_support/core_ext/numeric/conversions.rb
+++ b/activesupport/lib/active_support/core_ext/numeric/conversions.rb
@@ -129,12 +129,6 @@ module ActiveSupport::NumericWithFormat
   end
 end
 
-# Ruby 2.4+ unifies Fixnum & Bignum into Integer.
-if 0.class == Integer
-  Integer.prepend ActiveSupport::NumericWithFormat
-else
-  Fixnum.prepend ActiveSupport::NumericWithFormat
-  Bignum.prepend ActiveSupport::NumericWithFormat
-end
+Integer.prepend ActiveSupport::NumericWithFormat
 Float.prepend ActiveSupport::NumericWithFormat
 BigDecimal.prepend ActiveSupport::NumericWithFormat
diff --git a/activesupport/lib/active_support/core_ext/object/duplicable.rb b/activesupport/lib/active_support/core_ext/object/duplicable.rb
index 9bb99087bc..c78ee6bbfc 100644
--- a/activesupport/lib/active_support/core_ext/object/duplicable.rb
+++ b/activesupport/lib/active_support/core_ext/object/duplicable.rb
@@ -75,8 +75,11 @@ end
 
 class Symbol
   begin
-    :symbol.dup # Ruby 2.4.x.
-    "symbol_from_string".to_sym.dup # Some symbols can't `dup` in Ruby 2.4.0.
+    :symbol.dup
+
+    # Some symbols couldn't be duped in Ruby 2.4.0 only, due to a bug.
+    # This feature check catches any regression.
+    "symbol_from_string".to_sym.dup
   rescue TypeError
 
     # Symbols are not duplicable:
diff --git a/activesupport/lib/active_support/core_ext/regexp.rb b/activesupport/lib/active_support/core_ext/regexp.rb
index efbd708aee..d92943c7ae 100644
--- a/activesupport/lib/active_support/core_ext/regexp.rb
+++ b/activesupport/lib/active_support/core_ext/regexp.rb
@@ -4,8 +4,4 @@ class Regexp #:nodoc:
   def multiline?
     options & MULTILINE == MULTILINE
   end
-
-  def match?(string, pos = 0)
-    !!match(string, pos)
-  end unless //.respond_to?(:match?)
 end
diff --git a/activesupport/lib/active_support/core_ext/string/multibyte.rb b/activesupport/lib/active_support/core_ext/string/multibyte.rb
index 07c0d16398..6cceb46507 100644
--- a/activesupport/lib/active_support/core_ext/string/multibyte.rb
+++ b/activesupport/lib/active_support/core_ext/string/multibyte.rb
@@ -11,12 +11,13 @@ class String
   # encapsulates the original string. A Unicode safe version of all the String methods are defined on this proxy
   # class. If the proxy class doesn't respond to a certain method, it's forwarded to the encapsulated string.
   #
-  #   >> "lj".upcase
-  #   => "lj"
   #   >> "lj".mb_chars.upcase.to_s
   #   => "LJ"
   #
-  # NOTE: An above example is useful for pre Ruby 2.4. Ruby 2.4 supports Unicode case mappings.
+  # NOTE: Ruby 2.4 and later support native Unicode case mappings:
+  #
+  #   >> "lj".upcase
+  #   => "LJ"
   #
   # == Method chaining
   #
diff --git a/activesupport/lib/active_support/duration/iso8601_serializer.rb b/activesupport/lib/active_support/duration/iso8601_serializer.rb
index bb177ae5b7..84ae29c1ec 100644
--- a/activesupport/lib/active_support/duration/iso8601_serializer.rb
+++ b/activesupport/lib/active_support/duration/iso8601_serializer.rb
@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "active_support/core_ext/object/blank"
-require "active_support/core_ext/hash/transform_values"
 
 module ActiveSupport
   class Duration
diff --git a/activesupport/lib/active_support/rails.rb b/activesupport/lib/active_support/rails.rb
index 5c34a0abb3..8b727a69ec 100644
--- a/activesupport/lib/active_support/rails.rb
+++ b/activesupport/lib/active_support/rails.rb
@@ -27,9 +27,3 @@ require "active_support/core_ext/module/delegation"
 
 # Defines ActiveSupport::Deprecation.
 require "active_support/deprecation"
-
-# Defines Regexp#match?.
-#
-# This should be removed when Rails needs Ruby 2.4 or later, and the require
-# added where other Regexp extensions are being used (easy to grep).
-require "active_support/core_ext/regexp"
diff --git a/activesupport/lib/active_support/xml_mini.rb b/activesupport/lib/active_support/xml_mini.rb
index ee2048cb54..d0659aeaae 100644
--- a/activesupport/lib/active_support/xml_mini.rb
+++ b/activesupport/lib/active_support/xml_mini.rb
@@ -48,10 +48,6 @@ module ActiveSupport
         "Array"      => "array",
         "Hash"       => "hash"
       }
-
-      # No need to map these on Ruby 2.4+
-      TYPE_NAMES["Fixnum"] = "integer" unless 0.class == Integer
-      TYPE_NAMES["Bignum"] = "integer" unless 0.class == Integer
     end
 
     FORMATTING = {
diff --git a/activesupport/test/core_ext/array/grouping_test.rb b/activesupport/test/core_ext/array/grouping_test.rb
index c182b91826..37111a5d7d 100644
--- a/activesupport/test/core_ext/array/grouping_test.rb
+++ b/activesupport/test/core_ext/array/grouping_test.rb
@@ -4,15 +4,6 @@ require "abstract_unit"
 require "active_support/core_ext/array"
 
 class GroupingTest < ActiveSupport::TestCase
-  def setup
-    # In Ruby < 2.4, test we avoid Integer#/ (redefined by mathn)
-    Fixnum.send :private, :/ unless 0.class == Integer
-  end
-
-  def teardown
-    Fixnum.send :public, :/ unless 0.class == Integer
-  end
-
   def test_in_groups_of_with_perfect_fit
     groups = []
     ("a".."i").to_a.in_groups_of(3) do |group|
diff --git a/activesupport/test/core_ext/duration_test.rb b/activesupport/test/core_ext/duration_test.rb
index c5022cf5b1..8f6befe809 100644
--- a/activesupport/test/core_ext/duration_test.rb
+++ b/activesupport/test/core_ext/duration_test.rb
@@ -24,7 +24,7 @@ class DurationTest < ActiveSupport::TestCase
   end
 
   def test_instance_of
-    assert 1.minute.instance_of?(1.class)
+    assert 1.minute.instance_of?(Integer)
     assert 2.days.instance_of?(ActiveSupport::Duration)
     assert !3.second.instance_of?(Numeric)
   end
diff --git a/activesupport/test/core_ext/hash/transform_values_test.rb b/activesupport/test/core_ext/hash/transform_values_test.rb
index d34b7fa7b9..e481b5e4a9 100644
--- a/activesupport/test/core_ext/hash/transform_values_test.rb
+++ b/activesupport/test/core_ext/hash/transform_values_test.rb
@@ -2,25 +2,16 @@
 
 require "abstract_unit"
 require "active_support/core_ext/hash/indifferent_access"
-require "active_support/core_ext/hash/transform_values"
 
-class TransformValuesTest < ActiveSupport::TestCase
-  test "transform_values returns a new hash with the values computed from the block" do
-    original = { a: "a", b: "b" }
-    mapped = original.transform_values { |v| v + "!" }
-
-    assert_equal({ a: "a", b: "b" }, original)
-    assert_equal({ a: "a!", b: "b!" }, mapped)
-  end
-
-  test "transform_values! modifies the values of the original" do
-    original = { a: "a", b: "b" }
-    mapped = original.transform_values! { |v| v + "!" }
-
-    assert_equal({ a: "a!", b: "b!" }, original)
-    assert_same original, mapped
+class TransformValuesDeprecatedRequireTest < ActiveSupport::TestCase
+  test "requiring transform_values is deprecated" do
+    assert_deprecated do
+      require "active_support/core_ext/hash/transform_values"
+    end
   end
+end
 
+class IndifferentTransformValuesTest < ActiveSupport::TestCase
   test "indifferent access is still indifferent after mapping values" do
     original = { a: "a", b: "b" }.with_indifferent_access
     mapped = original.transform_values { |v| v + "!" }
@@ -28,50 +19,4 @@ class TransformValuesTest < ActiveSupport::TestCase
     assert_equal "a!", mapped[:a]
     assert_equal "a!", mapped["a"]
   end
-
-  # This is to be consistent with the behavior of Ruby's built in methods
-  # (e.g. #select, #reject) as of 2.2
-  test "default values do not persist during mapping" do
-    original = Hash.new("foo")
-    original[:a] = "a"
-    mapped = original.transform_values { |v| v + "!" }
-
-    assert_equal "a!", mapped[:a]
-    assert_nil mapped[:b]
-  end
-
-  test "default procs do not persist after mapping" do
-    original = Hash.new { "foo" }
-    original[:a] = "a"
-    mapped = original.transform_values { |v| v + "!" }
-
-    assert_equal "a!", mapped[:a]
-    assert_nil mapped[:b]
-  end
-
-  test "transform_values returns a sized Enumerator if no block is given" do
-    original = { a: "a", b: "b" }
-    enumerator = original.transform_values
-    assert_equal original.size, enumerator.size
-    assert_equal Enumerator, enumerator.class
-  end
-
-  test "transform_values! returns a sized Enumerator if no block is given" do
-    original = { a: "a", b: "b" }
-    enumerator = original.transform_values!
-    assert_equal original.size, enumerator.size
-    assert_equal Enumerator, enumerator.class
-  end
-
-  test "transform_values is chainable with Enumerable methods" do
-    original = { a: "a", b: "b" }
-    mapped = original.transform_values.with_index { |v, i| [v, i].join }
-    assert_equal({ a: "a0", b: "b1" }, mapped)
-  end
-
-  test "transform_values! is chainable with Enumerable methods" do
-    original = { a: "a", b: "b" }
-    original.transform_values!.with_index { |v, i| [v, i].join }
-    assert_equal({ a: "a0", b: "b1" }, original)
-  end
 end
diff --git a/activesupport/test/core_ext/object/duplicable_test.rb b/activesupport/test/core_ext/object/duplicable_test.rb
index b984becce3..635dd7f281 100644
--- a/activesupport/test/core_ext/object/duplicable_test.rb
+++ b/activesupport/test/core_ext/object/duplicable_test.rb
@@ -9,15 +9,9 @@ class DuplicableTest < ActiveSupport::TestCase
   if RUBY_VERSION >= "2.5.0"
     RAISE_DUP = [method(:puts)]
     ALLOW_DUP = ["1", "symbol_from_string".to_sym, Object.new, /foo/, [], {}, Time.now, Class.new, Module.new, BigDecimal("4.56"), nil, false, true, 1, 2.3, Complex(1), Rational(1)]
-  elsif RUBY_VERSION >= "2.4.1"
+  else
     RAISE_DUP = [method(:puts), Complex(1), Rational(1)]
     ALLOW_DUP = ["1", "symbol_from_string".to_sym, Object.new, /foo/, [], {}, Time.now, Class.new, Module.new, BigDecimal("4.56"), nil, false, true, 1, 2.3]
-  elsif RUBY_VERSION >= "2.4.0"  # Due to 2.4.0 bug. This elsif cannot be removed unless we drop 2.4.0 support...
-    RAISE_DUP = [method(:puts), Complex(1), Rational(1), "symbol_from_string".to_sym]
-    ALLOW_DUP = ["1", Object.new, /foo/, [], {}, Time.now, Class.new, Module.new, BigDecimal("4.56"), nil, false, true, 1, 2.3]
-  else
-    RAISE_DUP = [nil, false, true, :symbol, 1, 2.3, method(:puts), Complex(1), Rational(1)]
-    ALLOW_DUP = ["1", Object.new, /foo/, [], {}, Time.now, Class.new, Module.new, BigDecimal("4.56")]
   end
 
   def test_duplicable