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-rw-r--r--activesupport/CHANGELOG2
-rw-r--r--activesupport/lib/active_support/core_ext/enumerable.rb9
2 files changed, 9 insertions, 2 deletions
diff --git a/activesupport/CHANGELOG b/activesupport/CHANGELOG
index 81eeb92e32..059a3ebbe0 100644
--- a/activesupport/CHANGELOG
+++ b/activesupport/CHANGELOG
@@ -1,5 +1,7 @@
*SVN*
+* Changed the implementation of Enumerable#group_by to use a double array approach instead of a hash such that the insert order is honored [DHH/Marcel]
+
* remove multiple enumerations from ActiveSupport::JSON#convert_json_to_yaml when dealing with date/time values. [rick]
* Hash#symbolize_keys skips keys that can't be symbolized. #10500 [Brad Greenlee]
diff --git a/activesupport/lib/active_support/core_ext/enumerable.rb b/activesupport/lib/active_support/core_ext/enumerable.rb
index f35c8f86c5..c3a351538f 100644
--- a/activesupport/lib/active_support/core_ext/enumerable.rb
+++ b/activesupport/lib/active_support/core_ext/enumerable.rb
@@ -15,8 +15,13 @@ module Enumerable
# "2006-02-24 -> Transcript, Transcript"
# "2006-02-23 -> Transcript"
def group_by
- inject({}) do |groups, element|
- (groups[yield(element)] ||= []) << element
+ inject([]) do |groups, element|
+ value = yield(element)
+ if (last_group = groups.last) && last_group.first == value
+ last_group.last << element
+ else
+ groups << [value, [element]]
+ end
groups
end
end if RUBY_VERSION < '1.9'