Pitch: ticket dependencies

[rjpaskin]

Ticket dependencies

As a user
I want to specify dependencies between tickets
So that I can tell what tickets need to be deployed before others

Proposal

A lot of this is based on a similar feature from Waffle: their help doc

Be able to declare dependencies using keywords in the title or description of a ticket

Given a ticket numbered 123
And a ticket numbered 987
When I add "requires #123" to ticket 987
Then I should see ticket 123 as a parent of 987
And I should see ticket 987 as a child of 123

Proposed keywords (taken from Waffle):

• blocked by #123
• requires #123
• require #123
• needs #123
• need #123
• depends on #123

Possible UI:

_________________________________________________________
| _______________________  |  __________________________ |
| | 123                 |  |  | 987                    | |
| | Some ticket         |  |  | Some other ticket      | |
| |_____________________|  |  |________________________| |
| | <icon> requires 987 |  |  | <icon> required by 123 | |
| |_____________________|  |  |________________________| |
|                          |                             |

For the icon/status, a dependency is "ok" if the required ticket is in the same swimlane
as the requiree, or a swimlane to the right:

Where Ticket 2 requires Ticket 1:

| Ticket 1 | Ticket 2 | => status: warning
|          |          |

| Ticket 1 |          | => status: ok
| Ticket 2 |          |

| Ticket 2 | Ticket 1 | => status: ok
|          |          |

Looking through previous tickets, it seems that we generally have a sequence of dependencies for
tickets:

ticket 1 => needed by ticket 2 => needed by ticket 3 => needed by ticket 4

with an occasional fanning-out - e.g. a ticket has 2 dependencies, which themselves are independent.

Out of scope/not going to do

• Keywords anywhere not in title/description - i.e. comments
  Too many places for parser code to look
• Dependencies between ticket => PR or PR => PR (we already have PR => ticket from the connects keyword)
  Simpler database modelling
• Adding dependencies through a UI in FlightPlan
  Text interface works well enough
• 'Inverse' dependencies - adding a keyword to the parent ticket (e.g. required by #123)
  Feel like it would be confusing if you needed to remove or amend the dependency to have to look at the parent ticket
• Showing nested dependencies - dependencies are only one level deep, but dependencies can form an implicit chain
  Prevent having to do expensive recursive database queries, or having a complex UI

Bonus

• Data migration to add dependencies to existing tickets in database
• Add to realtime updates
• Be able to 'navigate' through the dependency chain - click on a dependency and scroll that ticket into view?