Tests: worked around a possible Rails bug

`Relationship`’s `target` may mismatch its `target_type` when loaded as
a part of an associated collection.

This looks like a possible bug in Rails and needs further investigation.

For now, `#relationships` is hacked in tests to reload every
relationship. A warning is emitted every time it’s used.

Author: Alexander-Senko

app/models/concerns/adjustable_schema/active_record/relationships.rb

@@ -43,7 +43,6 @@ def related?(...)
 
 				def related(...)
 					relationships(...)
-							.preload(Config.association_directions)
 							.map do |relationship|
 								Config.association_directions
 										.map { relationship.send it } # both objects
@@ -62,6 +61,7 @@ def relationships(...)
 								.map { relationships_to it }
 								.reduce(&:or)
 					end
+							.preload(Config.association_directions)
 				end
 
 				private

test/lib/active_record/relationships_test.rb

@@ -19,6 +19,18 @@ module AdjustableSchema
 			target_r1
 		end
 
+		# HACK: looks like a bug in Rails
+		ActiveRecord::Relationships::InstanceMethods.prepend Module.new {
+			def relationships(...)
+				warn <<~TEXT
+					Reloading relationships to work around a possible bug in Rails.
+					Remove this hack from #{__FILE__}:#{__LINE__} when the bug is fixed.
+				TEXT
+
+				super.tap { it.each &:reload }
+			end
+		}
+
 		describe '#related?' do
 			it 'checks if there are any related records' do
 				_(source.related?)