Fix messages[]= does not override value

2 files changed, 9 insertions, 0 deletions

diff --git a/activemodel/lib/active_model/errors.rb b/activemodel/lib/active_model/errors.rb
index 81a65a60a7..ac19b4625e 100644
--- a/activemodel/lib/active_model/errors.rb
+++ b/activemodel/lib/active_model/errors.rb
@@ -631,6 +631,7 @@ module ActiveModel
     def []=(attribute, value)
       ActiveSupport::Deprecation.warn("Calling `[]=` to an ActiveModel::Errors is deprecated. Please call `ActiveModel::Errors#add` instead.")
 
+      @errors.delete(attribute)
       Array(value).each do |message|
         @errors.add(attribute, message)
       end
diff --git a/activemodel/test/cases/errors_test.rb b/activemodel/test/cases/errors_test.rb
index 513bd163fc..1e4a6ddc00 100644
--- a/activemodel/test/cases/errors_test.rb
+++ b/activemodel/test/cases/errors_test.rb
@@ -101,6 +101,14 @@ class ErrorsTest < ActiveModel::TestCase
     end
   end
 
+  test "[]= overrides values" do
+    errors = ActiveModel::Errors.new(self)
+    assert_deprecated { errors.messages[:foo] = "omg" }
+    assert_deprecated { errors.messages[:foo] = "zomg" }
+
+    assert_equal ["zomg"], errors[:foo]
+  end
+
   test "values returns an empty array after try to get a message only" do
     errors = ActiveModel::Errors.new(Person.new)
     errors.messages[:foo]