fix(tasks): reset description checklist when a recurring task recurs

When a recurring task with inline checklist items in its description
(TipTap `- [ ]` checkboxes) was marked done, Vikunja advanced the due
date and reopened it for the next occurrence, but the description's
checkboxes stayed CHECKED. The recurrence path in updateDone advances
dates/reminders and resets Done, but nothing touched the Description
field, so the checked checklist HTML carried over verbatim.

Reset the checklist checked-state on the recurrence transition only,
covering the TipTap form (`data-checked="true"` and `checked` on
`<input type="checkbox">`) and Markdown `- [x]`/`- [X]` defensively.

Fixes #2709

pkg/models/tasks.go

@@ -1747,6 +1747,22 @@ func setTaskDatesFromCurrentDateRepeat(oldTask, newTask *Task) {
 	newTask.Done = false
 }
 
+var (
+	checklistTiptapCheckedRegex   = regexp.MustCompile(`(data-checked=")true(")`)
+	checklistInputCheckedRegex    = regexp.MustCompile(`(<input[^>]*type=["']checkbox["'][^>]*?)\s+checked(?:=["'][^"']*["'])?`)
+	checklistMarkdownCheckedRegex = regexp.MustCompile(`(?m)^(\s*[-*]\s+\[)[xX](\])`)
+)
+
+// resetDescriptionChecklist unchecks every checklist item in a description without
+// touching any other content. A recurring task carries its description verbatim into
+// the next occurrence, so checked checklist items would otherwise stay checked.
+func resetDescriptionChecklist(description string) string {
+	description = checklistTiptapCheckedRegex.ReplaceAllString(description, "${1}false${2}")
+	description = checklistInputCheckedRegex.ReplaceAllString(description, "$1")
+	description = checklistMarkdownCheckedRegex.ReplaceAllString(description, "$1 $2")
+	return description
+}
+
 // This helper function updates the reminders, doneAt, start, end and due dates of the *old* task
 // and saves the new values in the newTask object.
 // We make a few assumptions here:
@@ -1766,6 +1782,11 @@ func updateDone(oldTask *Task, newTask *Task) (updateDoneAt bool) {
 			setTaskDatesDefault(oldTask, newTask)
 		}
 
+		// A recurring task reopens for its next occurrence, so its checklist starts fresh.
+		if oldTask.isRepeating() && !newTask.Done {
+			newTask.Description = resetDescriptionChecklist(newTask.Description)
+		}
+
 		newTask.DoneAt = time.Now()
 	}
 

pkg/models/tasks_test.go

@@ -986,6 +986,60 @@ func TestUpdateDone(t *testing.T) {
 				assert.False(t, newTask.Done)
 			})
 		})
+		t.Run("reset checklist on recurrence", func(t *testing.T) {
+			const checked = `before<ul data-type="taskList"><li data-checked="true" data-type="taskItem"><label><input type="checkbox" checked="checked"><span></span></label><div><p>Item</p></li></ul>after`
+			const unchecked = `before<ul data-type="taskList"><li data-checked="false" data-type="taskItem"><label><input type="checkbox"><span></span></label><div><p>Item</p></li></ul>after`
+
+			oldTask := &Task{
+				Done:        false,
+				RepeatAfter: 8600,
+				DueDate:     time.Unix(1550000000, 0),
+			}
+			newTask := &Task{
+				Done:        true,
+				Description: checked,
+			}
+
+			updateDone(oldTask, newTask)
+
+			assert.False(t, newTask.Done)
+			assert.True(t, newTask.DueDate.After(oldTask.DueDate))
+			assert.Equal(t, unchecked, newTask.Description)
+		})
+		t.Run("reset markdown checklist on recurrence", func(t *testing.T) {
+			oldTask := &Task{
+				Done:        false,
+				RepeatAfter: 8600,
+				DueDate:     time.Unix(1550000000, 0),
+			}
+			newTask := &Task{
+				Done:        true,
+				Description: "- [x] one\n- [X] two\n- [ ] three\nnot a [x] checklist",
+			}
+
+			updateDone(oldTask, newTask)
+
+			assert.Equal(t, "- [ ] one\n- [ ] two\n- [ ] three\nnot a [x] checklist", newTask.Description)
+		})
+		t.Run("non-recurring description untouched", func(t *testing.T) {
+			const checked = `before<ul data-type="taskList"><li data-checked="true" data-type="taskItem"><label><input type="checkbox" checked="checked"><span></span></label><div><p>Item</p></li></ul>after`
+
+			oldTask := &Task{
+				Done:        false,
+				RepeatAfter: 0,
+				RepeatMode:  TaskRepeatModeDefault,
+				DueDate:     time.Unix(1550000000, 0),
+			}
+			newTask := &Task{
+				Done:        true,
+				Description: checked,
+			}
+
+			updateDone(oldTask, newTask)
+
+			assert.True(t, newTask.Done)
+			assert.Equal(t, checked, newTask.Description)
+		})
 	})
 }