Add real buckets for tasks which don't have one (#446)

Add docs for error code

Add moving new tasks into the default bucket when none was provided

Add moving tasks in default bucket when deleting one

Fix tests again

Add test for removing a bucket

Fix tests

Prevent removing the last bucket

Remove the empty pseudo bucket

Add migration to create a new bucket for each list (and put all tasks in it

Co-authored-by: kolaente <k@knt.li>
Reviewed-on: https://kolaente.dev/vikunja/api/pulls/446

pkg/migration/20200425182634.go

@@ -0,0 +1,75 @@
+// Vikunja is a to-do list application to facilitate your life.
+// Copyright 2018-2020 Vikunja and contributors. All rights reserved.
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+package migration
+
+import (
+	"code.vikunja.io/api/pkg/models"
+	"src.techknowlogick.com/xormigrate"
+	"xorm.io/xorm"
+)
+
+func init() {
+	migrations = append(migrations, &xormigrate.Migration{
+		ID:          "20200425182634",
+		Description: "Create one bucket for each list",
+		Migrate: func(tx *xorm.Engine) (err error) {
+			lists := []*models.List{}
+			err = tx.Find(&lists)
+			if err != nil {
+				return
+			}
+
+			tasks := []*models.Task{}
+			err = tx.Find(&tasks)
+			if err != nil {
+				return
+			}
+
+			// This map contains all buckets with their list ids as key
+			buckets := make(map[int64]*models.Bucket, len(lists))
+			for _, l := range lists {
+				buckets[l.ID] = &models.Bucket{
+					ListID: l.ID,
+					Title:  "New Bucket",
+					// The bucket creator is just the same as the list's one
+					CreatedByID: l.OwnerID,
+				}
+				_, err = tx.Insert(buckets[l.ID])
+				if err != nil {
+					return
+				}
+
+				for _, t := range tasks {
+					if t.ListID != l.ID {
+						continue
+					}
+
+					t.BucketID = buckets[l.ID].ID
+					_, err = tx.Where("id = ?", t.ID).Update(t)
+					if err != nil {
+						return
+					}
+				}
+			}
+
+			return
+		},
+		Rollback: func(tx *xorm.Engine) error {
+			return nil
+		},
+	})
+}