Backport 7ba3a48 to 5.0

activerecord/CHANGELOG.md

@@ -1,3 +1,10 @@
+*   PostgreSQL array columns will now respect the encoding of strings contained
+    in the array.
+
+    Fixes #26326.
+
+    *Sean Griffin*
+
 *   Inverse association instances will now be set before `after_find` or
     `after_initialize` callbacks are run.
 

activerecord/lib/active_record/connection_adapters/postgresql/oid/array.rb

@@ -33,7 +33,11 @@ def cast(value)
 
           def serialize(value)
             if value.is_a?(::Array)
-              @pg_encoder.encode(type_cast_array(value, :serialize))
+              result = @pg_encoder.encode(type_cast_array(value, :serialize))
+              if encoding = determine_encoding_of_strings(value)
+                result.encode!(encoding)
+              end
+              result
             else
               super
             end
@@ -63,6 +67,13 @@ def type_cast_array(value, method)
               @subtype.public_send(method, value)
             end
           end
+
+          def determine_encoding_of_strings(value)
+            case value
+            when ::Array then determine_encoding_of_strings(value.first)
+            when ::String then value.encoding
+            end
+          end
         end
       end
     end

activerecord/test/cases/adapters/postgresql/array_test.rb

@@ -305,6 +305,12 @@ def self.model_name; ActiveModel::Name.new(PgArray) end
     assert_equal ["has already been taken"], e2.errors[:tags], "Should have uniqueness message for tags"
   end
 
+  def test_encoding_arrays_of_utf8_strings
+    string_with_utf8 = "nový"
+    assert_equal [string_with_utf8], @type.deserialize(@type.serialize([string_with_utf8]))
+    assert_equal [[string_with_utf8]], @type.deserialize(@type.serialize([[string_with_utf8]]))
+  end
+
   private
   def assert_cycle field, array
     # test creation