Add convenience method group_by_attribute

Many operations need grouping of errors by attributes, e.g. ActiveRecord::AutosaveAssociation#association_valid?

Refactor other methods using group_by_attribute

1 files changed, 8 insertions, 0 deletions

diff --git a/activemodel/test/cases/errors_test.rb b/activemodel/test/cases/errors_test.rb
index a6fd95d7b1..58aa7ee147 100644
--- a/activemodel/test/cases/errors_test.rb
+++ b/activemodel/test/cases/errors_test.rb
@@ -494,6 +494,14 @@ class ErrorsTest < ActiveModel::TestCase
     assert_equal({ name: [{ error: :invalid }] }, person.errors.details)
   end
 
+  test "group_by_attribute" do
+    person = Person.new
+    error = person.errors.add(:name, :invalid, message: "is bad")
+    hash = person.errors.group_by_attribute
+
+    assert_equal({ name: [error] }, hash)
+  end
+
   test "dup duplicates details" do
     errors = ActiveModel::Errors.new(Person.new)
     errors.add(:name, :invalid)