fix: sort tasks logically and consistent across dbms (#1177)

This PR changes the behavoir of sorting tasks. Before, tasks were sorted with null values first. Now, null values are always sorted last which is usually what you want.

Partial fix for https://github.com/go-vikunja/frontend/issues/54

Co-authored-by: kolaente <k@knt.li>
Reviewed-on: https://kolaente.dev/vikunja/api/pulls/1177

pkg/integrations/task_collection_test.go

@@ -113,7 +113,7 @@ func TestTaskCollection(t *testing.T) {
 			t.Run("by priority", func(t *testing.T) {
 				rec, err := testHandler.testReadAllWithUser(url.Values{"sort_by": []string{"priority"}}, urlParams)
 				assert.NoError(t, err)
-				assert.Contains(t, rec.Body.String(), `{"id":33,"title":"task #33 with percent done","description":"","done":false,"done_at":"0001-01-01T00:00:00Z","due_date":"0001-01-01T00:00:00Z","reminder_dates":null,"list_id":1,"repeat_after":0,"repeat_mode":0,"priority":0,"start_date":"0001-01-01T00:00:00Z","end_date":"0001-01-01T00:00:00Z","assignees":null,"labels":null,"hex_color":"","percent_done":0.5,"identifier":"test1-17","index":17,"related_tasks":{},"attachments":null,"is_favorite":false,"created":"2018-12-01T01:12:04Z","updated":"2018-12-01T01:12:04Z","bucket_id":1,"position":0,"kanban_position":0,"created_by":{"id":1,"name":"","username":"user1","created":"2018-12-01T15:13:12Z","updated":"2018-12-02T15:13:12Z"}},{"id":4,"title":"task #4 low prio","description":"","done":false,"done_at":"0001-01-01T00:00:00Z","due_date":"0001-01-01T00:00:00Z","reminder_dates":null,"list_id":1,"repeat_after":0,"repeat_mode":0,"priority":1,"start_date":"0001-01-01T00:00:00Z","end_date":"0001-01-01T00:00:00Z","assignees":null,"labels":null,"hex_color":"","percent_done":0,"identifier":"test1-4","index":4,"related_tasks":{},"attachments":null,"is_favorite":false,"created":"2018-12-01T01:12:04Z","updated":"2018-12-01T01:12:04Z","bucket_id":2,"position":0,"kanban_position":0,"created_by":{"id":1,"name":"","username":"user1","created":"2018-12-01T15:13:12Z","updated":"2018-12-02T15:13:12Z"}},{"id":3,"title":"task #3 high prio","description":"","done":false,"done_at":"0001-01-01T00:00:00Z","due_date":"0001-01-01T00:00:00Z","reminder_dates":null,"list_id":1,"repeat_after":0,"repeat_mode":0,"priority":100,"start_date":"0001-01-01T00:00:00Z","end_date":"0001-01-01T00:00:00Z","assignees":null,"labels":null,"hex_color":"","percent_done":0,"identifier":"test1-3","index":3,"related_tasks":{},"attachments":null,"is_favorite":false,"created":"2018-12-01T01:12:04Z","updated":"2018-12-01T01:12:04Z","bucket_id":2,"position":0,"kanban_position":0,"created_by":{"id":1,"name":"","username":"user1","created":"2018-12-01T15:13:12Z","updated":"2018-12-02T15:13:12Z"}}]`)
+				assert.Contains(t, rec.Body.String(), `{"id":33,"title":"task #33 with percent done","description":"","done":false,"done_at":"0001-01-01T00:00:00Z","due_date":"0001-01-01T00:00:00Z","reminder_dates":null,"list_id":1,"repeat_after":0,"repeat_mode":0,"priority":0,"start_date":"0001-01-01T00:00:00Z","end_date":"0001-01-01T00:00:00Z","assignees":null,"labels":null,"hex_color":"","percent_done":0.5,"identifier":"test1-17","index":17,"related_tasks":{},"attachments":null,"is_favorite":false,"created":"2018-12-01T01:12:04Z","updated":"2018-12-01T01:12:04Z","bucket_id":1,"position":0,"kanban_position":0,"created_by":{"id":1,"name":"","username":"user1","created":"2018-12-01T15:13:12Z","updated":"2018-12-02T15:13:12Z"}}]`)
 			})
 			t.Run("by priority desc", func(t *testing.T) {
 				rec, err := testHandler.testReadAllWithUser(url.Values{"sort_by": []string{"priority"}, "order_by": []string{"desc"}}, urlParams)
@@ -123,13 +123,13 @@ func TestTaskCollection(t *testing.T) {
 			t.Run("by priority asc", func(t *testing.T) {
 				rec, err := testHandler.testReadAllWithUser(url.Values{"sort_by": []string{"priority"}, "order_by": []string{"asc"}}, urlParams)
 				assert.NoError(t, err)
-				assert.Contains(t, rec.Body.String(), `{"id":33,"title":"task #33 with percent done","description":"","done":false,"done_at":"0001-01-01T00:00:00Z","due_date":"0001-01-01T00:00:00Z","reminder_dates":null,"list_id":1,"repeat_after":0,"repeat_mode":0,"priority":0,"start_date":"0001-01-01T00:00:00Z","end_date":"0001-01-01T00:00:00Z","assignees":null,"labels":null,"hex_color":"","percent_done":0.5,"identifier":"test1-17","index":17,"related_tasks":{},"attachments":null,"is_favorite":false,"created":"2018-12-01T01:12:04Z","updated":"2018-12-01T01:12:04Z","bucket_id":1,"position":0,"kanban_position":0,"created_by":{"id":1,"name":"","username":"user1","created":"2018-12-01T15:13:12Z","updated":"2018-12-02T15:13:12Z"}},{"id":4,"title":"task #4 low prio","description":"","done":false,"done_at":"0001-01-01T00:00:00Z","due_date":"0001-01-01T00:00:00Z","reminder_dates":null,"list_id":1,"repeat_after":0,"repeat_mode":0,"priority":1,"start_date":"0001-01-01T00:00:00Z","end_date":"0001-01-01T00:00:00Z","assignees":null,"labels":null,"hex_color":"","percent_done":0,"identifier":"test1-4","index":4,"related_tasks":{},"attachments":null,"is_favorite":false,"created":"2018-12-01T01:12:04Z","updated":"2018-12-01T01:12:04Z","bucket_id":2,"position":0,"kanban_position":0,"created_by":{"id":1,"name":"","username":"user1","created":"2018-12-01T15:13:12Z","updated":"2018-12-02T15:13:12Z"}},{"id":3,"title":"task #3 high prio","description":"","done":false,"done_at":"0001-01-01T00:00:00Z","due_date":"0001-01-01T00:00:00Z","reminder_dates":null,"list_id":1,"repeat_after":0,"repeat_mode":0,"priority":100,"start_date":"0001-01-01T00:00:00Z","end_date":"0001-01-01T00:00:00Z","assignees":null,"labels":null,"hex_color":"","percent_done":0,"identifier":"test1-3","index":3,"related_tasks":{},"attachments":null,"is_favorite":false,"created":"2018-12-01T01:12:04Z","updated":"2018-12-01T01:12:04Z","bucket_id":2,"position":0,"kanban_position":0,"created_by":{"id":1,"name":"","username":"user1","created":"2018-12-01T15:13:12Z","updated":"2018-12-02T15:13:12Z"}}]`)
+				assert.Contains(t, rec.Body.String(), `{"id":33,"title":"task #33 with percent done","description":"","done":false,"done_at":"0001-01-01T00:00:00Z","due_date":"0001-01-01T00:00:00Z","reminder_dates":null,"list_id":1,"repeat_after":0,"repeat_mode":0,"priority":0,"start_date":"0001-01-01T00:00:00Z","end_date":"0001-01-01T00:00:00Z","assignees":null,"labels":null,"hex_color":"","percent_done":0.5,"identifier":"test1-17","index":17,"related_tasks":{},"attachments":null,"is_favorite":false,"created":"2018-12-01T01:12:04Z","updated":"2018-12-01T01:12:04Z","bucket_id":1,"position":0,"kanban_position":0,"created_by":{"id":1,"name":"","username":"user1","created":"2018-12-01T15:13:12Z","updated":"2018-12-02T15:13:12Z"}}]`)
 			})
 			// should equal duedate asc
 			t.Run("by due_date", func(t *testing.T) {
 				rec, err := testHandler.testReadAllWithUser(url.Values{"sort_by": []string{"due_date"}}, urlParams)
 				assert.NoError(t, err)
-				assert.Contains(t, rec.Body.String(), `{"id":6,"title":"task #6 lower due date","description":"","done":false,"done_at":"0001-01-01T00:00:00Z","due_date":"2018-11-30T22:25:24Z","reminder_dates":null,"list_id":1,"repeat_after":0,"repeat_mode":0,"priority":0,"start_date":"0001-01-01T00:00:00Z","end_date":"0001-01-01T00:00:00Z","assignees":null,"labels":null,"hex_color":"","percent_done":0,"identifier":"test1-6","index":6,"related_tasks":{},"attachments":null,"is_favorite":false,"created":"2018-12-01T01:12:04Z","updated":"2018-12-01T01:12:04Z","bucket_id":3,"position":0,"kanban_position":0,"created_by":{"id":1,"name":"","username":"user1","created":"2018-12-01T15:13:12Z","updated":"2018-12-02T15:13:12Z"}},{"id":5,"title":"task #5 higher due date","description":"","done":false,"done_at":"0001-01-01T00:00:00Z","due_date":"2018-12-01T03:58:44Z","reminder_dates":null,"list_id":1,"repeat_after":0,"repeat_mode":0,"priority":0,"start_date":"0001-01-01T00:00:00Z","end_date":"0001-01-01T00:00:00Z","assignees":null,"labels":null,"hex_color":"","percent_done":0,"identifier":"test1-5","index":5,"related_tasks":{},"attachments":null,"is_favorite":false,"created":"2018-12-01T01:12:04Z","updated":"2018-12-01T01:12:04Z","bucket_id":2,"position":0,"kanban_position":0,"created_by":{"id":1,"name":"","username":"user1","created":"2018-12-01T15:13:12Z","updated":"2018-12-02T15:13:12Z"}}]`)
+				assert.Contains(t, rec.Body.String(), `[{"id":6,"title":"task #6 lower due date","description":"","done":false,"done_at":"0001-01-01T00:00:00Z","due_date":"2018-11-30T22:25:24Z","reminder_dates":null,"list_id":1,"repeat_after":0,"repeat_mode":0,"priority":0,"start_date":"0001-01-01T00:00:00Z","end_date":"0001-01-01T00:00:00Z","assignees":null,"labels":null,"hex_color":"","percent_done":0,"identifier":"test1-6","index":6,"related_tasks":{},"attachments":null,"is_favorite":false,"created":"2018-12-01T01:12:04Z","updated":"2018-12-01T01:12:04Z","bucket_id":3,"position":0,"kanban_position":0,"created_by":{"id":1,"name":"","username":"user1","created":"2018-12-01T15:13:12Z","updated":"2018-12-02T15:13:12Z"}}`)
 			})
 			t.Run("by duedate desc", func(t *testing.T) {
 				rec, err := testHandler.testReadAllWithUser(url.Values{"sort_by": []string{"due_date"}, "order_by": []string{"desc"}}, urlParams)
@@ -140,12 +140,12 @@ func TestTaskCollection(t *testing.T) {
 			t.Run("by duedate asc without  suffix", func(t *testing.T) {
 				rec, err := testHandler.testReadAllWithUser(url.Values{"sort_by": []string{"due_date"}, "order_by": []string{"asc"}}, urlParams)
 				assert.NoError(t, err)
-				assert.Contains(t, rec.Body.String(), `{"id":6,"title":"task #6 lower due date","description":"","done":false,"done_at":"0001-01-01T00:00:00Z","due_date":"2018-11-30T22:25:24Z","reminder_dates":null,"list_id":1,"repeat_after":0,"repeat_mode":0,"priority":0,"start_date":"0001-01-01T00:00:00Z","end_date":"0001-01-01T00:00:00Z","assignees":null,"labels":null,"hex_color":"","percent_done":0,"identifier":"test1-6","index":6,"related_tasks":{},"attachments":null,"is_favorite":false,"created":"2018-12-01T01:12:04Z","updated":"2018-12-01T01:12:04Z","bucket_id":3,"position":0,"kanban_position":0,"created_by":{"id":1,"name":"","username":"user1","created":"2018-12-01T15:13:12Z","updated":"2018-12-02T15:13:12Z"}},{"id":5,"title":"task #5 higher due date","description":"","done":false,"done_at":"0001-01-01T00:00:00Z","due_date":"2018-12-01T03:58:44Z","reminder_dates":null,"list_id":1,"repeat_after":0,"repeat_mode":0,"priority":0,"start_date":"0001-01-01T00:00:00Z","end_date":"0001-01-01T00:00:00Z","assignees":null,"labels":null,"hex_color":"","percent_done":0,"identifier":"test1-5","index":5,"related_tasks":{},"attachments":null,"is_favorite":false,"created":"2018-12-01T01:12:04Z","updated":"2018-12-01T01:12:04Z","bucket_id":2,"position":0,"kanban_position":0,"created_by":{"id":1,"name":"","username":"user1","created":"2018-12-01T15:13:12Z","updated":"2018-12-02T15:13:12Z"}}]`)
+				assert.Contains(t, rec.Body.String(), `[{"id":6,"title":"task #6 lower due date","description":"","done":false,"done_at":"0001-01-01T00:00:00Z","due_date":"2018-11-30T22:25:24Z","reminder_dates":null,"list_id":1,"repeat_after":0,"repeat_mode":0,"priority":0,"start_date":"0001-01-01T00:00:00Z","end_date":"0001-01-01T00:00:00Z","assignees":null,"labels":null,"hex_color":"","percent_done":0,"identifier":"test1-6","index":6,"related_tasks":{},"attachments":null,"is_favorite":false,"created":"2018-12-01T01:12:04Z","updated":"2018-12-01T01:12:04Z","bucket_id":3,"position":0,"kanban_position":0,"created_by":{"id":1,"name":"","username":"user1","created":"2018-12-01T15:13:12Z","updated":"2018-12-02T15:13:12Z"}}`)
 			})
 			t.Run("by due_date without suffix", func(t *testing.T) {
 				rec, err := testHandler.testReadAllWithUser(url.Values{"sort_by": []string{"due_date"}}, urlParams)
 				assert.NoError(t, err)
-				assert.Contains(t, rec.Body.String(), `{"id":6,"title":"task #6 lower due date","description":"","done":false,"done_at":"0001-01-01T00:00:00Z","due_date":"2018-11-30T22:25:24Z","reminder_dates":null,"list_id":1,"repeat_after":0,"repeat_mode":0,"priority":0,"start_date":"0001-01-01T00:00:00Z","end_date":"0001-01-01T00:00:00Z","assignees":null,"labels":null,"hex_color":"","percent_done":0,"identifier":"test1-6","index":6,"related_tasks":{},"attachments":null,"is_favorite":false,"created":"2018-12-01T01:12:04Z","updated":"2018-12-01T01:12:04Z","bucket_id":3,"position":0,"kanban_position":0,"created_by":{"id":1,"name":"","username":"user1","created":"2018-12-01T15:13:12Z","updated":"2018-12-02T15:13:12Z"}},{"id":5,"title":"task #5 higher due date","description":"","done":false,"done_at":"0001-01-01T00:00:00Z","due_date":"2018-12-01T03:58:44Z","reminder_dates":null,"list_id":1,"repeat_after":0,"repeat_mode":0,"priority":0,"start_date":"0001-01-01T00:00:00Z","end_date":"0001-01-01T00:00:00Z","assignees":null,"labels":null,"hex_color":"","percent_done":0,"identifier":"test1-5","index":5,"related_tasks":{},"attachments":null,"is_favorite":false,"created":"2018-12-01T01:12:04Z","updated":"2018-12-01T01:12:04Z","bucket_id":2,"position":0,"kanban_position":0,"created_by":{"id":1,"name":"","username":"user1","created":"2018-12-01T15:13:12Z","updated":"2018-12-02T15:13:12Z"}}]`)
+				assert.Contains(t, rec.Body.String(), `[{"id":6,"title":"task #6 lower due date","description":"","done":false,"done_at":"0001-01-01T00:00:00Z","due_date":"2018-11-30T22:25:24Z","reminder_dates":null,"list_id":1,"repeat_after":0,"repeat_mode":0,"priority":0,"start_date":"0001-01-01T00:00:00Z","end_date":"0001-01-01T00:00:00Z","assignees":null,"labels":null,"hex_color":"","percent_done":0,"identifier":"test1-6","index":6,"related_tasks":{},"attachments":null,"is_favorite":false,"created":"2018-12-01T01:12:04Z","updated":"2018-12-01T01:12:04Z","bucket_id":3,"position":0,"kanban_position":0,"created_by":{"id":1,"name":"","username":"user1","created":"2018-12-01T15:13:12Z","updated":"2018-12-02T15:13:12Z"}}`)
 			})
 			t.Run("by duedate desc without  suffix", func(t *testing.T) {
 				rec, err := testHandler.testReadAllWithUser(url.Values{"sort_by": []string{"due_date"}, "order_by": []string{"desc"}}, urlParams)
@@ -155,7 +155,7 @@ func TestTaskCollection(t *testing.T) {
 			t.Run("by duedate asc", func(t *testing.T) {
 				rec, err := testHandler.testReadAllWithUser(url.Values{"sort_by": []string{"due_date"}, "order_by": []string{"asc"}}, urlParams)
 				assert.NoError(t, err)
-				assert.Contains(t, rec.Body.String(), `{"id":6,"title":"task #6 lower due date","description":"","done":false,"done_at":"0001-01-01T00:00:00Z","due_date":"2018-11-30T22:25:24Z","reminder_dates":null,"list_id":1,"repeat_after":0,"repeat_mode":0,"priority":0,"start_date":"0001-01-01T00:00:00Z","end_date":"0001-01-01T00:00:00Z","assignees":null,"labels":null,"hex_color":"","percent_done":0,"identifier":"test1-6","index":6,"related_tasks":{},"attachments":null,"is_favorite":false,"created":"2018-12-01T01:12:04Z","updated":"2018-12-01T01:12:04Z","bucket_id":3,"position":0,"kanban_position":0,"created_by":{"id":1,"name":"","username":"user1","created":"2018-12-01T15:13:12Z","updated":"2018-12-02T15:13:12Z"}},{"id":5,"title":"task #5 higher due date","description":"","done":false,"done_at":"0001-01-01T00:00:00Z","due_date":"2018-12-01T03:58:44Z","reminder_dates":null,"list_id":1,"repeat_after":0,"repeat_mode":0,"priority":0,"start_date":"0001-01-01T00:00:00Z","end_date":"0001-01-01T00:00:00Z","assignees":null,"labels":null,"hex_color":"","percent_done":0,"identifier":"test1-5","index":5,"related_tasks":{},"attachments":null,"is_favorite":false,"created":"2018-12-01T01:12:04Z","updated":"2018-12-01T01:12:04Z","bucket_id":2,"position":0,"kanban_position":0,"created_by":{"id":1,"name":"","username":"user1","created":"2018-12-01T15:13:12Z","updated":"2018-12-02T15:13:12Z"}}]`)
+				assert.Contains(t, rec.Body.String(), `[{"id":6,"title":"task #6 lower due date","description":"","done":false,"done_at":"0001-01-01T00:00:00Z","due_date":"2018-11-30T22:25:24Z","reminder_dates":null,"list_id":1,"repeat_after":0,"repeat_mode":0,"priority":0,"start_date":"0001-01-01T00:00:00Z","end_date":"0001-01-01T00:00:00Z","assignees":null,"labels":null,"hex_color":"","percent_done":0,"identifier":"test1-6","index":6,"related_tasks":{},"attachments":null,"is_favorite":false,"created":"2018-12-01T01:12:04Z","updated":"2018-12-01T01:12:04Z","bucket_id":3,"position":0,"kanban_position":0,"created_by":{"id":1,"name":"","username":"user1","created":"2018-12-01T15:13:12Z","updated":"2018-12-02T15:13:12Z"}}`)
 			})
 			t.Run("invalid sort parameter", func(t *testing.T) {
 				_, err := testHandler.testReadAllWithUser(url.Values{"sort_by": []string{"loremipsum"}}, urlParams)
@@ -366,7 +366,7 @@ func TestTaskCollection(t *testing.T) {
 			t.Run("by priority", func(t *testing.T) {
 				rec, err := testHandler.testReadAllWithUser(url.Values{"sort_by": []string{"priority"}}, nil)
 				assert.NoError(t, err)
-				assert.Contains(t, rec.Body.String(), `{"id":33,"title":"task #33 with percent done","description":"","done":false,"done_at":"0001-01-01T00:00:00Z","due_date":"0001-01-01T00:00:00Z","reminder_dates":null,"list_id":1,"repeat_after":0,"repeat_mode":0,"priority":0,"start_date":"0001-01-01T00:00:00Z","end_date":"0001-01-01T00:00:00Z","assignees":null,"labels":null,"hex_color":"","percent_done":0.5,"identifier":"test1-17","index":17,"related_tasks":{},"attachments":null,"is_favorite":false,"created":"2018-12-01T01:12:04Z","updated":"2018-12-01T01:12:04Z","bucket_id":1,"position":0,"kanban_position":0,"created_by":{"id":1,"name":"","username":"user1","created":"2018-12-01T15:13:12Z","updated":"2018-12-02T15:13:12Z"}},{"id":4,"title":"task #4 low prio","description":"","done":false,"done_at":"0001-01-01T00:00:00Z","due_date":"0001-01-01T00:00:00Z","reminder_dates":null,"list_id":1,"repeat_after":0,"repeat_mode":0,"priority":1,"start_date":"0001-01-01T00:00:00Z","end_date":"0001-01-01T00:00:00Z","assignees":null,"labels":null,"hex_color":"","percent_done":0,"identifier":"test1-4","index":4,"related_tasks":{},"attachments":null,"is_favorite":false,"created":"2018-12-01T01:12:04Z","updated":"2018-12-01T01:12:04Z","bucket_id":2,"position":0,"kanban_position":0,"created_by":{"id":1,"name":"","username":"user1","created":"2018-12-01T15:13:12Z","updated":"2018-12-02T15:13:12Z"}},{"id":3,"title":"task #3 high prio","description":"","done":false,"done_at":"0001-01-01T00:00:00Z","due_date":"0001-01-01T00:00:00Z","reminder_dates":null,"list_id":1,"repeat_after":0,"repeat_mode":0,"priority":100,"start_date":"0001-01-01T00:00:00Z","end_date":"0001-01-01T00:00:00Z","assignees":null,"labels":null,"hex_color":"","percent_done":0,"identifier":"test1-3","index":3,"related_tasks":{},"attachments":null,"is_favorite":false,"created":"2018-12-01T01:12:04Z","updated":"2018-12-01T01:12:04Z","bucket_id":2,"position":0,"kanban_position":0,"created_by":{"id":1,"name":"","username":"user1","created":"2018-12-01T15:13:12Z","updated":"2018-12-02T15:13:12Z"}}]`)
+				assert.Contains(t, rec.Body.String(), `{"id":33,"title":"task #33 with percent done","description":"","done":false,"done_at":"0001-01-01T00:00:00Z","due_date":"0001-01-01T00:00:00Z","reminder_dates":null,"list_id":1,"repeat_after":0,"repeat_mode":0,"priority":0,"start_date":"0001-01-01T00:00:00Z","end_date":"0001-01-01T00:00:00Z","assignees":null,"labels":null,"hex_color":"","percent_done":0.5,"identifier":"test1-17","index":17,"related_tasks":{},"attachments":null,"is_favorite":false,"created":"2018-12-01T01:12:04Z","updated":"2018-12-01T01:12:04Z","bucket_id":1,"position":0,"kanban_position":0,"created_by":{"id":1,"name":"","username":"user1","created":"2018-12-01T15:13:12Z","updated":"2018-12-02T15:13:12Z"}}]`)
 			})
 			t.Run("by priority desc", func(t *testing.T) {
 				rec, err := testHandler.testReadAllWithUser(url.Values{"sort_by": []string{"priority"}, "order_by": []string{"desc"}}, nil)
@@ -376,13 +376,13 @@ func TestTaskCollection(t *testing.T) {
 			t.Run("by priority asc", func(t *testing.T) {
 				rec, err := testHandler.testReadAllWithUser(url.Values{"sort_by": []string{"priority"}, "order_by": []string{"asc"}}, nil)
 				assert.NoError(t, err)
-				assert.Contains(t, rec.Body.String(), `{"id":33,"title":"task #33 with percent done","description":"","done":false,"done_at":"0001-01-01T00:00:00Z","due_date":"0001-01-01T00:00:00Z","reminder_dates":null,"list_id":1,"repeat_after":0,"repeat_mode":0,"priority":0,"start_date":"0001-01-01T00:00:00Z","end_date":"0001-01-01T00:00:00Z","assignees":null,"labels":null,"hex_color":"","percent_done":0.5,"identifier":"test1-17","index":17,"related_tasks":{},"attachments":null,"is_favorite":false,"created":"2018-12-01T01:12:04Z","updated":"2018-12-01T01:12:04Z","bucket_id":1,"position":0,"kanban_position":0,"created_by":{"id":1,"name":"","username":"user1","created":"2018-12-01T15:13:12Z","updated":"2018-12-02T15:13:12Z"}},{"id":4,"title":"task #4 low prio","description":"","done":false,"done_at":"0001-01-01T00:00:00Z","due_date":"0001-01-01T00:00:00Z","reminder_dates":null,"list_id":1,"repeat_after":0,"repeat_mode":0,"priority":1,"start_date":"0001-01-01T00:00:00Z","end_date":"0001-01-01T00:00:00Z","assignees":null,"labels":null,"hex_color":"","percent_done":0,"identifier":"test1-4","index":4,"related_tasks":{},"attachments":null,"is_favorite":false,"created":"2018-12-01T01:12:04Z","updated":"2018-12-01T01:12:04Z","bucket_id":2,"position":0,"kanban_position":0,"created_by":{"id":1,"name":"","username":"user1","created":"2018-12-01T15:13:12Z","updated":"2018-12-02T15:13:12Z"}},{"id":3,"title":"task #3 high prio","description":"","done":false,"done_at":"0001-01-01T00:00:00Z","due_date":"0001-01-01T00:00:00Z","reminder_dates":null,"list_id":1,"repeat_after":0,"repeat_mode":0,"priority":100,"start_date":"0001-01-01T00:00:00Z","end_date":"0001-01-01T00:00:00Z","assignees":null,"labels":null,"hex_color":"","percent_done":0,"identifier":"test1-3","index":3,"related_tasks":{},"attachments":null,"is_favorite":false,"created":"2018-12-01T01:12:04Z","updated":"2018-12-01T01:12:04Z","bucket_id":2,"position":0,"kanban_position":0,"created_by":{"id":1,"name":"","username":"user1","created":"2018-12-01T15:13:12Z","updated":"2018-12-02T15:13:12Z"}}]`)
+				assert.Contains(t, rec.Body.String(), `{"id":33,"title":"task #33 with percent done","description":"","done":false,"done_at":"0001-01-01T00:00:00Z","due_date":"0001-01-01T00:00:00Z","reminder_dates":null,"list_id":1,"repeat_after":0,"repeat_mode":0,"priority":0,"start_date":"0001-01-01T00:00:00Z","end_date":"0001-01-01T00:00:00Z","assignees":null,"labels":null,"hex_color":"","percent_done":0.5,"identifier":"test1-17","index":17,"related_tasks":{},"attachments":null,"is_favorite":false,"created":"2018-12-01T01:12:04Z","updated":"2018-12-01T01:12:04Z","bucket_id":1,"position":0,"kanban_position":0,"created_by":{"id":1,"name":"","username":"user1","created":"2018-12-01T15:13:12Z","updated":"2018-12-02T15:13:12Z"}}]`)
 			})
 			// should equal duedate asc
 			t.Run("by due_date", func(t *testing.T) {
 				rec, err := testHandler.testReadAllWithUser(url.Values{"sort_by": []string{"due_date"}}, nil)
 				assert.NoError(t, err)
-				assert.Contains(t, rec.Body.String(), `{"id":6,"title":"task #6 lower due date","description":"","done":false,"done_at":"0001-01-01T00:00:00Z","due_date":"2018-11-30T22:25:24Z","reminder_dates":null,"list_id":1,"repeat_after":0,"repeat_mode":0,"priority":0,"start_date":"0001-01-01T00:00:00Z","end_date":"0001-01-01T00:00:00Z","assignees":null,"labels":null,"hex_color":"","percent_done":0,"identifier":"test1-6","index":6,"related_tasks":{},"attachments":null,"is_favorite":false,"created":"2018-12-01T01:12:04Z","updated":"2018-12-01T01:12:04Z","bucket_id":3,"position":0,"kanban_position":0,"created_by":{"id":1,"name":"","username":"user1","created":"2018-12-01T15:13:12Z","updated":"2018-12-02T15:13:12Z"}},{"id":5,"title":"task #5 higher due date","description":"","done":false,"done_at":"0001-01-01T00:00:00Z","due_date":"2018-12-01T03:58:44Z","reminder_dates":null,"list_id":1,"repeat_after":0,"repeat_mode":0,"priority":0,"start_date":"0001-01-01T00:00:00Z","end_date":"0001-01-01T00:00:00Z","assignees":null,"labels":null,"hex_color":"","percent_done":0,"identifier":"test1-5","index":5,"related_tasks":{},"attachments":null,"is_favorite":false,"created":"2018-12-01T01:12:04Z","updated":"2018-12-01T01:12:04Z","bucket_id":2,"position":0,"kanban_position":0,"created_by":{"id":1,"name":"","username":"user1","created":"2018-12-01T15:13:12Z","updated":"2018-12-02T15:13:12Z"}}]`)
+				assert.Contains(t, rec.Body.String(), `[{"id":6,"title":"task #6 lower due date","description":"","done":false,"done_at":"0001-01-01T00:00:00Z","due_date":"2018-11-30T22:25:24Z","reminder_dates":null,"list_id":1,"repeat_after":0,"repeat_mode":0,"priority":0,"start_date":"0001-01-01T00:00:00Z","end_date":"0001-01-01T00:00:00Z","assignees":null,"labels":null,"hex_color":"","percent_done":0,"identifier":"test1-6","index":6,"related_tasks":{},"attachments":null,"is_favorite":false,"created":"2018-12-01T01:12:04Z","updated":"2018-12-01T01:12:04Z","bucket_id":3,"position":0,"kanban_position":0,"created_by":{"id":1,"name":"","username":"user1","created":"2018-12-01T15:13:12Z","updated":"2018-12-02T15:13:12Z"}},{"id":5,"title":"task #5 higher due date","description":"","done":false,"done_at":"0001-01-01T00:00:00Z","due_date":"2018-12-01T03:58:44Z","reminder_dates":null,"list_id":1,"repeat_after":0,"repeat_mode":0,"priority":0,"start_date":"0001-01-01T00:00:00Z","end_date":"0001-01-01T00:00:00Z","assignees":null,"labels":null,"hex_color":"","percent_done":0,"identifier":"test1-5","index":5,"related_tasks":{},"attachments":null,"is_favorite":false,"created":"2018-12-01T01:12:04Z","updated":"2018-12-01T01:12:04Z","bucket_id":2,"position":0,"kanban_position":0,"created_by":{"id":1,"name":"","username":"user1","created":"2018-12-01T15:13:12Z","updated":"2018-12-02T15:13:12Z"}}`)
 			})
 			t.Run("by duedate desc", func(t *testing.T) {
 				rec, err := testHandler.testReadAllWithUser(url.Values{"sort_by": []string{"due_date"}, "order_by": []string{"desc"}}, nil)
@@ -392,7 +392,7 @@ func TestTaskCollection(t *testing.T) {
 			t.Run("by duedate asc", func(t *testing.T) {
 				rec, err := testHandler.testReadAllWithUser(url.Values{"sort_by": []string{"due_date"}, "order_by": []string{"asc"}}, nil)
 				assert.NoError(t, err)
-				assert.Contains(t, rec.Body.String(), `{"id":6,"title":"task #6 lower due date","description":"","done":false,"done_at":"0001-01-01T00:00:00Z","due_date":"2018-11-30T22:25:24Z","reminder_dates":null,"list_id":1,"repeat_after":0,"repeat_mode":0,"priority":0,"start_date":"0001-01-01T00:00:00Z","end_date":"0001-01-01T00:00:00Z","assignees":null,"labels":null,"hex_color":"","percent_done":0,"identifier":"test1-6","index":6,"related_tasks":{},"attachments":null,"is_favorite":false,"created":"2018-12-01T01:12:04Z","updated":"2018-12-01T01:12:04Z","bucket_id":3,"position":0,"kanban_position":0,"created_by":{"id":1,"name":"","username":"user1","created":"2018-12-01T15:13:12Z","updated":"2018-12-02T15:13:12Z"}},{"id":5,"title":"task #5 higher due date","description":"","done":false,"done_at":"0001-01-01T00:00:00Z","due_date":"2018-12-01T03:58:44Z","reminder_dates":null,"list_id":1,"repeat_after":0,"repeat_mode":0,"priority":0,"start_date":"0001-01-01T00:00:00Z","end_date":"0001-01-01T00:00:00Z","assignees":null,"labels":null,"hex_color":"","percent_done":0,"identifier":"test1-5","index":5,"related_tasks":{},"attachments":null,"is_favorite":false,"created":"2018-12-01T01:12:04Z","updated":"2018-12-01T01:12:04Z","bucket_id":2,"position":0,"kanban_position":0,"created_by":{"id":1,"name":"","username":"user1","created":"2018-12-01T15:13:12Z","updated":"2018-12-02T15:13:12Z"}}]`)
+				assert.Contains(t, rec.Body.String(), `[{"id":6,"title":"task #6 lower due date","description":"","done":false,"done_at":"0001-01-01T00:00:00Z","due_date":"2018-11-30T22:25:24Z","reminder_dates":null,"list_id":1,"repeat_after":0,"repeat_mode":0,"priority":0,"start_date":"0001-01-01T00:00:00Z","end_date":"0001-01-01T00:00:00Z","assignees":null,"labels":null,"hex_color":"","percent_done":0,"identifier":"test1-6","index":6,"related_tasks":{},"attachments":null,"is_favorite":false,"created":"2018-12-01T01:12:04Z","updated":"2018-12-01T01:12:04Z","bucket_id":3,"position":0,"kanban_position":0,"created_by":{"id":1,"name":"","username":"user1","created":"2018-12-01T15:13:12Z","updated":"2018-12-02T15:13:12Z"}},{"id":5,"title":"task #5 higher due date","description":"","done":false,"done_at":"0001-01-01T00:00:00Z","due_date":"2018-12-01T03:58:44Z","reminder_dates":null,"list_id":1,"repeat_after":0,"repeat_mode":0,"priority":0,"start_date":"0001-01-01T00:00:00Z","end_date":"0001-01-01T00:00:00Z","assignees":null,"labels":null,"hex_color":"","percent_done":0,"identifier":"test1-5","index":5,"related_tasks":{},"attachments":null,"is_favorite":false,"created":"2018-12-01T01:12:04Z","updated":"2018-12-01T01:12:04Z","bucket_id":2,"position":0,"kanban_position":0,"created_by":{"id":1,"name":"","username":"user1","created":"2018-12-01T15:13:12Z","updated":"2018-12-02T15:13:12Z"}}`)
 			})
 			t.Run("invalid parameter", func(t *testing.T) {
 				// Invalid parameter should not sort at all

pkg/models/task_collection_test.go

@@ -1046,6 +1046,9 @@ func TestTaskCollection_ReadAll(t *testing.T) {
 				a: &user.User{ID: 1},
 			},
 			want: []*Task{
+				// The only tasks with a position set
+				task1,
+				task2,
 				// the other ones don't have a position set
 				task3,
 				task4,
@@ -1076,9 +1079,51 @@ func TestTaskCollection_ReadAll(t *testing.T) {
 				task31,
 				task32,
 				task33,
-				// The only tasks with a position set
+			},
-				task1,
+		},
+		{
+			name: "order by due date",
+			fields: fields{
+				SortBy:  []string{"due_date", "id"},
+				OrderBy: []string{"asc", "desc"},
+			},
+			args: args{
+				a: &user.User{ID: 1},
+			},
+			want: []*Task{
+				// The only tasks with a due date
+				task6,
+				task5,
+				// The other ones don't have a due date
+				task33,
+				task32,
+				task31,
+				task30,
+				task29,
+				task28,
+				task27,
+				task26,
+				task25,
+				task24,
+				task23,
+				task22,
+				task21,
+				task20,
+				task19,
+				task18,
+				task17,
+				task16,
+				task15,
+				task12,
+				task11,
+				task10,
+				task9,
+				task8,
+				task7,
+				task4,
+				task3,
 				task2,
+				task1,
 			},
 		},
 		{

pkg/models/tasks.go

@@ -296,18 +296,21 @@ func getRawTasksForLists(s *xorm.Session, lists []*List, a web.Auth, opts *taskO
 		if err := param.validate(); err != nil {
 			return nil, 0, 0, err
 		}
+
+		// Mysql sorts columns with null values before ones without null value.
+		// Because it does not have support for NULLS FIRST or NULLS LAST we work around this by
+		// first sorting for null (or not null) values and then the order we actually want to.
+		if db.Type() == schemas.MYSQL {
+			orderby += param.sortBy + " IS NULL, "
+		}
+
 		orderby += param.sortBy + " " + param.orderBy.String()
 
-		// Postgres sorts by default entries with null values after ones with values.
+		// Postgres and sqlite allow us to control how columns with null values are sorted.
 		// To make that consistent with the sort order we have and other dbms, we're adding a separate clause here.
-		if db.Type() == schemas.POSTGRES {
+		if db.Type() == schemas.POSTGRES || db.Type() == schemas.SQLITE {
-			if param.orderBy == orderAscending {
-				orderby += " NULLS FIRST"
-			}
-			if param.orderBy == orderDescending {
 			orderby += " NULLS LAST"
 		}
-		}
 
 		if (i + 1) < len(opts.sortby) {
 			orderby += ", "