Add 'Hash#deep_transform_values', and 'Hash#deep_transform_values!'

5 files changed, 84 insertions, 0 deletions

diff --git a/activesupport/CHANGELOG.md b/activesupport/CHANGELOG.md
index 2da774ca66..7002474b8d 100644
--- a/activesupport/CHANGELOG.md
+++ b/activesupport/CHANGELOG.md
@@ -12,6 +12,10 @@
 
     *Stefan Schüßler*
 
+*   Add `Hash#deep_transform_values`, and `Hash#deep_transform_values!`.
+
+    *Guillermo Iguaran*
+
 ## Rails 6.0.0.beta1 (January 18, 2019) ##
 
 *   Remove deprecated `Module#reachable?` method.
diff --git a/activesupport/lib/active_support/core_ext/hash.rb b/activesupport/lib/active_support/core_ext/hash.rb
index c4b9e5f1a0..2f0901d853 100644
--- a/activesupport/lib/active_support/core_ext/hash.rb
+++ b/activesupport/lib/active_support/core_ext/hash.rb
@@ -2,6 +2,7 @@
 
 require "active_support/core_ext/hash/conversions"
 require "active_support/core_ext/hash/deep_merge"
+require "active_support/core_ext/hash/deep_transform_values"
 require "active_support/core_ext/hash/except"
 require "active_support/core_ext/hash/indifferent_access"
 require "active_support/core_ext/hash/keys"
diff --git a/activesupport/lib/active_support/core_ext/hash/deep_transform_values.rb b/activesupport/lib/active_support/core_ext/hash/deep_transform_values.rb
new file mode 100644
index 0000000000..ab68c34309
--- /dev/null
+++ b/activesupport/lib/active_support/core_ext/hash/deep_transform_values.rb
@@ -0,0 +1,52 @@
+# frozen_string_literal: true
+
+class Hash
+  # Returns a new hash with all keys converted by the block operation.
+  # This includes the keys from the root hash and from all
+  # nested hashes and arrays.
+  #
+  #  hash = { person: { name: 'Rob', age: '28' } }
+  #
+  #  hash.deep_transform_values{ |value| value.to_s.upcase }
+  #  # => {person: {name: "ROB", age: "28"}}
+  def deep_transform_values(&block)
+    _deep_transform_values_in_object(self, &block)
+  end
+
+  # Destructively converts all values by using the block operation.
+  # This includes the values from the root hash and from all
+  # nested hashes and arrays.
+  def deep_transform_values!(&block)
+    _deep_transform_values_in_object!(self, &block)
+  end
+
+  private
+    # support methods for deep transforming nested hashes and arrays
+    def _deep_transform_values_in_object(object, &block)
+      case object
+      when Hash
+        object.each_with_object({}) do |(key, value), result|
+          result[key] = _deep_transform_values_in_object(value, &block)
+        end
+      when Array
+        object.map { |e| _deep_transform_values_in_object(e, &block) }
+      else
+        yield(object)
+      end
+    end
+
+    def _deep_transform_values_in_object!(object, &block)
+      case object
+      when Hash
+        object.keys.each do |key|
+          value = object.delete(key)
+          object[key] = _deep_transform_values_in_object!(value, &block)
+        end
+        object
+      when Array
+        object.map! { |e| _deep_transform_values_in_object!(e, &block) }
+      else
+        yield(object)
+      end
+    end
+end
diff --git a/activesupport/test/core_ext/hash/deep_transform_values_test.rb b/activesupport/test/core_ext/hash/deep_transform_values_test.rb
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/activesupport/test/core_ext/hash/deep_transform_values_test.rb
diff --git a/activesupport/test/core_ext/hash_ext_test.rb b/activesupport/test/core_ext/hash_ext_test.rb
index e8e0a1ae72..90a5f2dcd1 100644
--- a/activesupport/test/core_ext/hash_ext_test.rb
+++ b/activesupport/test/core_ext/hash_ext_test.rb
@@ -33,6 +33,8 @@ class HashExtTest < ActiveSupport::TestCase
     h = {}
     assert_respond_to h, :deep_transform_keys
     assert_respond_to h, :deep_transform_keys!
+    assert_respond_to h, :deep_transform_values
+    assert_respond_to h, :deep_transform_values!
     assert_respond_to h, :symbolize_keys
     assert_respond_to h, :symbolize_keys!
     assert_respond_to h, :deep_symbolize_keys
@@ -78,6 +80,31 @@ class HashExtTest < ActiveSupport::TestCase
     assert_equal({ "a" => { b: { "c" => 3 } } }, @nested_mixed)
   end
 
+  def test_deep_transform_values
+    assert_equal({ "a" => "1", "b" => "2" }, @strings.deep_transform_values{ |value| value.to_s })
+    assert_equal({ "a" => { "b" => { "c" => "3" } } }, @nested_strings.deep_transform_values { |value| value.to_s })
+    assert_equal({ "a" => [ { "b" => "2" }, { "c" => "3" }, "4" ] }, @string_array_of_hashes.deep_transform_values { |value| value.to_s })
+  end
+
+  def test_deep_transform_values_not_mutates
+    transformed_hash = @nested_mixed.deep_dup
+    transformed_hash.deep_transform_values { |value| value.to_s }
+    assert_equal @nested_mixed, transformed_hash
+  end
+
+  def test_deep_transform_values!
+    assert_equal({ "a" => "1", "b" => "2" }, @strings.deep_transform_values!{ |value| value.to_s })
+    assert_equal({ "a" => { "b" => { "c" => "3" } } }, @nested_strings.deep_transform_values! { |value| value.to_s })
+    assert_equal({ "a" => [ { "b" => "2" }, { "c" => "3" }, "4" ] }, @string_array_of_hashes.deep_transform_values! { |value| value.to_s })
+  end
+
+  def test_deep_transform_values_with_bang_mutates
+    transformed_hash = @nested_mixed.deep_dup
+    transformed_hash.deep_transform_values! { |value| value.to_s }
+    assert_equal({ "a" => { b: { "c" => "3" } } }, transformed_hash)
+    assert_equal({ "a" => { b: { "c" => 3 } } }, @nested_mixed)
+  end
+
   def test_symbolize_keys
     assert_equal @symbols, @symbols.symbolize_keys
     assert_equal @symbols, @strings.symbolize_keys