Kanban bucket limits (#652)

Fix integration tests

Generate swagger docs

Add test for moving a task between buckets

Add check for bucket limit when updating a task

Add fixture to ensure a bucket with a high limit will never exceed the limit

Refactor bucket limit check into seperate function

Add test for creating and fix

Fix unexported field

Add error in case a task was added to a bucket which has its limit already exceeded

Add migration to add new task field

Add limit field to buckets

Co-authored-by: kolaente <k@knt.li>
Reviewed-on: https://kolaente.dev/vikunja/api/pulls/652

pkg/models/error.go

@@ -1334,3 +1334,32 @@ func (err ErrCannotRemoveLastBucket) HTTPError() web.HTTPError {
 		Message:  "You cannot remove the last bucket on this list.",
 	}
 }
+
+// ErrBucketLimitExceeded represents an error where a task is being created or moved to a bucket which has its limit already exceeded.
+type ErrBucketLimitExceeded struct {
+	BucketID int64
+	Limit    int64
+	TaskID   int64 // may be 0
+}
+
+// IsErrBucketLimitExceeded checks if an error is ErrBucketLimitExceeded.
+func IsErrBucketLimitExceeded(err error) bool {
+	_, ok := err.(ErrBucketLimitExceeded)
+	return ok
+}
+
+func (err ErrBucketLimitExceeded) Error() string {
+	return fmt.Sprintf("Cannot add a task to this bucket because it would exceed the limit [BucketID: %d, Limit: %d, TaskID: %d]", err.BucketID, err.Limit, err.TaskID)
+}
+
+// ErrCodeBucketLimitExceeded holds the unique world-error code of this error
+const ErrCodeBucketLimitExceeded = 10004
+
+// HTTPError holds the http error description
+func (err ErrBucketLimitExceeded) HTTPError() web.HTTPError {
+	return web.HTTPError{
+		HTTPCode: http.StatusPreconditionFailed,
+		Code:     ErrCodeBucketLimitExceeded,
+		Message:  "You cannot add the task to this bucket as it already exceeded the limit of tasks it can hold.",
+	}
+}

pkg/models/kanban.go

@@ -35,6 +35,9 @@ type Bucket struct {
 	// All tasks which belong to this bucket.
 	Tasks []*Task `xorm:"-" json:"tasks"`
 
+	// How many tasks can be at the same time on this board max
+	Limit int64 `xorm:"default 0" json:"limit"`
+
 	// A timestamp when this bucket was created. You cannot change this value.
 	Created time.Time `xorm:"created not null" json:"created"`
 	// A timestamp when this bucket was last updated. You cannot change this value.

pkg/models/tasks.go

@@ -545,6 +545,32 @@ func checkBucketAndTaskBelongToSameList(s *xorm.Session, fullTask *Task, bucketI
 	return
 }
 
+// Checks if adding a new task would exceed the bucket limit
+func checkBucketLimit(s *xorm.Session, t *Task, bucket *Bucket) (err error) {
+
+	// We need the bucket to check if it has more tasks than the limit allows
+	if bucket == nil {
+		bucket, err = getBucketByID(s, t.BucketID)
+		if err != nil {
+			return err
+		}
+	}
+
+	// Check the limit
+	if bucket.Limit > 0 {
+		taskCount, err := s.
+			Where("bucket_id = ?", bucket.ID).
+			Count(&Task{})
+		if err != nil {
+			return err
+		}
+		if taskCount >= bucket.Limit {
+			return ErrBucketLimitExceeded{TaskID: t.ID, BucketID: bucket.ID, Limit: bucket.Limit}
+		}
+	}
+	return nil
+}
+
 // Create is the implementation to create a list task
 // @Summary Create a task
 // @Description Inserts a task into a list.
@@ -608,12 +634,18 @@ func createTask(s *xorm.Session, t *Task, a web.Auth, updateAssignees bool) (err
 	}
 
 	// Get the default bucket and move the task there
+	var bucket *Bucket
 	if t.BucketID == 0 {
-		defaultBucket, err := getDefaultBucket(s, t.ListID)
+		bucket, err = getDefaultBucket(s, t.ListID)
 		if err != nil {
 			return err
 		}
-		t.BucketID = defaultBucket.ID
+		t.BucketID = bucket.ID
+	}
+
+	// Bucket Limit
+	if err := checkBucketLimit(s, t, bucket); err != nil {
+		return err
 	}
 
 	// Get the index for this task
@@ -730,15 +762,19 @@ func (t *Task) Update() (err error) {
 		"repeat_from_current_date",
 	}
 
-	// If the task is being moved between lists, make sure to move the bucket + index as well
-	if t.ListID != 0 && ot.ListID != t.ListID {
-		b, err := getDefaultBucket(s, t.ListID)
+	// Make sure we have a bucket
+	var bucket *Bucket
+	if t.BucketID == 0 || (t.ListID != 0 && ot.ListID != t.ListID) {
+		bucket, err = getDefaultBucket(s, t.ListID)
 		if err != nil {
 			_ = s.Rollback()
 			return err
 		}
-		t.BucketID = b.ID
+		t.BucketID = bucket.ID
+	}
 
+	// If the task is being moved between lists, make sure to move the bucket + index as well
+	if t.ListID != 0 && ot.ListID != t.ListID {
 		latestTask := &Task{}
 		_, err = s.Where("list_id = ?", t.ListID).OrderBy("id desc").Get(latestTask)
 		if err != nil {
@@ -750,6 +786,12 @@ func (t *Task) Update() (err error) {
 		colsToUpdate = append(colsToUpdate, "index")
 	}
 
+	// Check the bucket limit
+	if err := checkBucketLimit(s, t, bucket); err != nil {
+		_ = s.Rollback()
+		return err
+	}
+
 	// Update the labels
 	//
 	// Maybe FIXME:

pkg/models/tasks_test.go

@@ -85,6 +85,18 @@ func TestTask_Create(t *testing.T) {
 		assert.Error(t, err)
 		assert.True(t, user.IsErrUserDoesNotExist(err))
 	})
+	t.Run("full bucket", func(t *testing.T) {
+		db.LoadAndAssertFixtures(t)
+		task := &Task{
+			Title:       "Lorem",
+			Description: "Lorem Ipsum Dolor",
+			ListID:      1,
+			BucketID:    2, // Bucket 2 already has 3 tasks and a limit of 3
+		}
+		err := task.Create(usr)
+		assert.Error(t, err)
+		assert.True(t, IsErrBucketLimitExceeded(err))
+	})
 }
 
 func TestTask_Update(t *testing.T) {
@@ -111,6 +123,19 @@ func TestTask_Update(t *testing.T) {
 		assert.Error(t, err)
 		assert.True(t, IsErrTaskDoesNotExist(err))
 	})
+	t.Run("full bucket", func(t *testing.T) {
+		db.LoadAndAssertFixtures(t)
+		task := &Task{
+			ID:          1,
+			Title:       "test10000",
+			Description: "Lorem Ipsum Dolor",
+			ListID:      1,
+			BucketID:    2, // Bucket 2 already has 3 tasks and a limit of 3
+		}
+		err := task.Update()
+		assert.Error(t, err)
+		assert.True(t, IsErrBucketLimitExceeded(err))
+	})
 }
 
 func TestTask_Delete(t *testing.T) {