Before this commit, we had pkg/integration/tests/submodule/add.go
failing with a panic. I'm pretty sure the issue is this: we're now
calling quite a few GetDisabledReason calls on each layout() call,
and if a background thread happens to update a model slice while
we're doing this, we can end up with a selection index that's now
out of bounds because it hasn't been clamped to match the new list
length.
Specifically, here we had the selected index being -1 (the list starts
empty and somehow the value is -1 in this case) and then the list
gets a new submodule so the length is now 1, but the list cursor
doesn't know about this so remains on the old value. Then we confirm
the length is greater than zero and try to get the selected submodule
and get an out of bounds error.
This commit fixes the issue by clamping the selected index whenever
we get the length of the list so that it stays in-sync. This is not
a perfect solution because the length can change at any time, but
it seems to reliably fix the test, and using mutexes didn't seem to
make a difference.
Note that we're swapping the order of IFileTree and IListCursor in
the file tree view model to ensure that the list cursor's Len()
method is called (which performs the clamping).
Also, comment from the PR:
This 'trait' pattern we're using is convenient but can lead to awkward
situations. In this case we have both the list view model and the
(embedded) list cursor with a Len() method. The list cursor Len()
method just calls the list view model Len() method. But I wanted
to make it that the list view model now calls ClampSelection() on the
list cursor whenever it obtains the length. This will cause an
infinite loop because ClampSelection() internally calls Len()
(which calls the list view model's Len() method which in turn
calls ClampSelection() again, etc).
The only reason we were passing the list view model into the list
cursor was to supply the length method, so now we're just doing
that directly, and letting the list view model delegate the Len()
call to the list cursor, which now itself calls ClampSelection.
Something dumb that we're currently doing is expecting list items
to define an ID method which returns a string. We use that when copying
items to clipboard with ctrl+o and when getting a ref name for diffing.
This commit gets us a little deeper into that hole by explicitly requiring
list items to implement that method so that we can easily use the new
helper functions in list_controller_trait.go.
In future we need to just remove the whole ID thing entirely but I'm too
lazy to do that right now.
The only time we should call SetSelectedLineIdx is when we are happy for a
select range to be retained which means things like moving the selected line
index to top top/bottom or up/down a page as the user navigates.
But in every other case we should now call SetSelection because that will
set the selected index and cancel the range which is almost always what we
want.
This adds range select ability in two ways:
1) Sticky: like what we already have with the staging view i.e. press v then use arrow keys
2) Non-sticky: where you just use shift+up/down to expand the range
The state machine works like this:
(no range, press 'v') -> sticky range
(no range, press arrow) -> no range
(no range, press shift+arrow) -> nonsticky range
(sticky range, press 'v') -> no range
(sticky range, press arrow) -> sticky range
(sticky range, press shift+arrow) -> nonsticky range
(nonsticky range, press 'v') -> no range
(nonsticky range, press arrow) -> no range
(nonsticky range, press shift+arrow) -> nonsticky range
