disallow mutating a relation once loaded

1 files changed, 27 insertions, 0 deletions

diff --git a/activerecord/test/cases/relations_test.rb b/activerecord/test/cases/relations_test.rb
index 6c5bee7382..8544d36aa8 100644
--- a/activerecord/test/cases/relations_test.rb
+++ b/activerecord/test/cases/relations_test.rb
@@ -1284,4 +1284,31 @@ class RelationTest < ActiveRecord::TestCase
       Post.scoped.find_by!("1 = 0")
     end
   end
+
+  test "loaded relations cannot be mutated by multi value methods" do
+    relation = Post.scoped
+    relation.to_a
+
+    assert_raises(ActiveRecord::ImmutableRelation) do
+      relation.where! 'foo'
+    end
+  end
+
+  test "loaded relations cannot be mutated by single value methods" do
+    relation = Post.scoped
+    relation.to_a
+
+    assert_raises(ActiveRecord::ImmutableRelation) do
+      relation.limit! 5
+    end
+  end
+
+  test "loaded relations cannot be mutated by merge!" do
+    relation = Post.scoped
+    relation.to_a
+
+    assert_raises(ActiveRecord::ImmutableRelation) do
+      relation.merge! where: 'foo'
+    end
+  end
 end