Fix missing Tree.NodeHighlighted message

[robinvd]

When the tree has no selection the cursor_line is -1, then clicking on the last node in the tree will check if the selection is different from the last selection, and do a check nodes[previous_cursor_line] != nodes[new_cursor_line] but if previous_cursor_line=-1 and new_cursor_line=len(nodes)-1 then this will fail and the message will not be emitted.

Please review the following checklist.

• Docstrings on all new or modified functions / classes
• Updated documentation
• Updated CHANGELOG.md (where appropriate)

[TomJGooding]

Any chance of a regression test? I'm not a maintainer of Textual, but I'm sure you'll be asked this when someone gets to reviewing this. Thanks for you PR!

[robinvd]

any change to review this @davep (or other maintainers)

[davep]

@robinvd We've got a lot going on so sometimes it can take us a wee while to get through PRs. Meanwhile though what Tom said is good advice: if you've identified a bug and this is a PR to fix it then a regression test would be very welcome.

[robinvd]

@davep ofc I understand!On 31 Oct 2023, at 09:22, Dave Pearson ***@***.***> wrote: @robinvd We've got a lot going on so sometimes it can take us a wee while to get through PRs. Meanwhile though what Tom said is good advice: if you've identified a bug and this is a PR to fix it then a regression test would be very welcome. —Reply to this email directly, view it on GitHub, or unsubscribe.You are receiving this because you were mentioned.Message ID: ***@***.***>

[davep]

Just to add too: having enabled the running of tests in CI: it looks like your change might be causing some existing tests to fail; you will want to take that into account.

[willmcgugan]

@robinvd Could you open an issue for this please. With a small example that reproduces the problem. Just to help me understand what this is fixing.

[willmcgugan]

Closing. Assumed stale.

[robinvd]

@willmcgugan repro example

from textual.app import App
from textual.widgets import Tree


class BugApp(App):
    def compose(self):
        t = Tree("test")
        t.show_root = False
        t.root.add_leaf("node1")
        t.root.add_leaf("node2")
        t.root.add_leaf("node3")
        yield t

    def on_tree_node_highlighted(self, event):
        self.notify(f"hightlight! {event}")


BugApp().run()

if you now click on the last node, no notification will popup

[TomJGooding]

I might be wrong but this looks like an issue only when show_root=False is set in compose?

Currently this PR causes multiple existing tests to fail as @davep already mentioned. I wonder perhaps this just needs a check if show_root is False.