Fix moving items down when there is no space

After moving a sequence when there is no space for
a moving object we need to reset the position
for move_after and move_berofe methods

app/models/concerns/relative_positioning.rb

@@ -127,6 +127,7 @@ module RelativePositioning
 
     if pos_after && (pos_after - pos_before) < 2
       before.move_sequence_after
+      pos_after = before.next_relative_position
     end
 
     self.relative_position = self.class.position_between(pos_before, pos_after)
@@ -138,6 +139,7 @@ module RelativePositioning
 
     if pos_before && (pos_after - pos_before) < 2
       after.move_sequence_before
+      pos_before = after.prev_relative_position
     end
 
     self.relative_position = self.class.position_between(pos_before, pos_after)

changelogs/unreleased/32839-fix-relative-position-edge-case.yml

+---
+title: Fix relative positioning when moving items down and there is no space
+merge_request: 17781
+author:
+type: fixed

spec/support/shared_examples/relative_positioning_shared_examples.rb

@@ -84,6 +84,22 @@ RSpec.shared_examples 'a class that supports relative positioning' do
 
       expect(item1.relative_position).to be < item2.relative_position
     end
+
+    context 'when there is no space' do
+      let(:item3) { create(factory, default_params) }
+
+      before do
+        item1.update(relative_position: 1000)
+        item2.update(relative_position: 1001)
+        item3.update(relative_position: 1002)
+      end
+
+      it 'moves items correctly' do
+        item3.move_before(item2)
+
+        expect(item3.relative_position).to be_between(item1.reload.relative_position, item2.reload.relative_position).exclusive
+      end
+    end
   end
 
   describe '#move_after' do
@@ -94,6 +110,22 @@ RSpec.shared_examples 'a class that supports relative positioning' do
 
       expect(item1.relative_position).to be > item2.relative_position
     end
+
+    context 'when there is no space' do
+      let(:item3) { create(factory, default_params) }
+
+      before do
+        item1.update(relative_position: 1000)
+        item2.update(relative_position: 1001)
+        item3.update(relative_position: 1002)
+      end
+
+      it 'moves items correctly' do
+        item1.move_after(item2)
+
+        expect(item1.relative_position).to be_between(item2.reload.relative_position, item3.reload.relative_position).exclusive
+      end
+    end
   end
 
   describe '#move_to_end' do
@@ -196,7 +228,7 @@ RSpec.shared_examples 'a class that supports relative positioning' do
 
       new_item.move_between(item1, item2)
 
-      expect(new_item.relative_position).to be_between(item1.relative_position, item2.relative_position)
+      expect(new_item.relative_position).to be_between(item1.relative_position, item2.relative_position).exclusive
     end
 
     it 'uses rebalancing if there is no place' do
@@ -208,7 +240,7 @@ RSpec.shared_examples 'a class that supports relative positioning' do
       new_item.move_between(item2, item3)
       new_item.save!
 
-      expect(new_item.relative_position).to be_between(item2.relative_position, item3.relative_position)
+      expect(new_item.relative_position).to be_between(item2.relative_position, item3.relative_position).exclusive
       expect(item1.reload.relative_position).not_to eq(100)
     end