1490337 - Support landing any unblocked series in a full stack graph

Status: RESOLVED FIXED

(Conduit :: Lando, enhancement)

Description

[Steven MacLeod [:smacleod]]

Lando UI should present the full stack graph when loading a revision's page, allowing the user to select any landable (unblocked) series to land.

Comment 2

[Steven MacLeod [:smacleod]]

Attachment: stacks: add algorithm for drawing the stack graph (Bug 1490337).

This change introduces an algorithm for sorting the stack graph
topologically, implemented by `sort_stack_topological()`. It's important
to sort the stack topologically in order to draw it vertically beside
the revisions table.

`sort_stack_topological()` takes a `key` kwarg which can be used to
influence which topological sort is chosen. The intention here is to
allow us to influence the sort with `key` to result in a deterministic
order for a particular stack. I plan to break the tie between node
ordering using the revision ID in the future.

Additionally a `draw_stack_graph()` function implements an algorithm for
converting the topologically sorted graph into metadata which makes
drawing the graph trivial. A list of rows will be returned specifying
where the commit should appear in the drawing as well as the lines
needed to be drawn for the row. Each column specified in `above`,
`below`, or `other` results in a single line drawn. The specifics of
these lines is described in code.

Comment 3

[Steven MacLeod [:smacleod]]

Attachment: stacks: draw stack graph and allow selecting tip (Bug 1490337).

This converts the current stack page to display the full stack graph
rather than just the revisions to be landed (or a single revision when
it can't land). The new stack graph drawn in the table indicates the
relationships between the rows and mimics the stack display in
Phabricator itself.

What can/will land is now indicated by the "Land" column. If a revision
is part of a landable path it will have a radio button in this column
allowing the user to select it as the tip to land. The currently
selected series that will land based on the tip has the "Land" column
highlighted green.

Due to time constraints dynamically changing the series to land based on
these radio button selections was scrapped. Instead clicking a radio
button will take the user to the stack page for that specific revision.
This results in a bit of a slow, sub-optimal UX, but gives the same
overall functionality. Because of this choice all the code for the
LandingPreview could stay the same, treating the selected series as
static.

In the future it would be good to transition to a more dynamic page
which would make the dryrun at selection time. This would require adding
some new dynamic endpoints the JS could hit to grab the dryrun as well
as restructuring the entire stack page's JS.

Depends on D14267.

Comment 4

[Steven MacLeod [:smacleod]]

This has landed and should go out with the next deploy (early 2019).