urwid 2.6.4-1 exception when rendering an empty Pile or Columns as a flow widget

[Olivier Gayot]

When attempting to render an empty Pile or Columns as a flow widget using urwid 2.6.4-1, it fails with the following exception:

  File "/usr/lib/python3/dist-packages/urwid/widget/widget.py", line 112, in cached_render
    canv = fn(self, size, focus=focus)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3/dist-packages/urwid/widget/pile.py", line 822, in render
    _widths, heights, size_args = self.get_rows_sizes(size, focus)
                                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3/dist-packages/urwid/widget/pile.py", line 730, in get_rows_sizes
    heights.append(w.pack(w_h_arg, item_focus)[1])
                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3/dist-packages/urwid/widget/pile.py", line 744, in pack
    return super().pack(size, focus)
           ^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3/dist-packages/urwid/widget/widget.py", line 401, in pack
    raise WidgetError(f"Cannot pack (maxcol,) size, this is not a flow widget: {self!r}")
urwid.widget.widget.WidgetError: Cannot pack (maxcol,) size, this is not a flow widget: <Pile widget>

Minimal code to reproduce:

```python
from urwid import Pile

Pile([
    ("pack", Pile([])),
]).render((10,))
```

This looks like a regression in 2.6.4-1 since the same code was not failing on 2.1.2-4

There is an upstream fix [1] that is released in urwid 2.6.5.

 https://github.com/urwid/urwid/pull/843

[Olivier Gayot (ogayot)]

Adding debdiff. The updated package is available in ppa:ogayot/noble-proposed

https://launchpad.net/~ogayot/+archive/ubuntu/noble-proposed/+packages

[Benjamin Drung (bdrung)]

Sponsored upload.

[Launchpad Janitor (janitor)]

This bug was fixed in the package urwid - 2.6.4-1ubuntu1

---------------
urwid (2.6.4-1ubuntu1) noble; urgency=medium

  * Apply upstream patch to fix a crash when rendering an empty Pile or an
    empty Columns as a flow widget. (LP: #2058388)
    + d/patches/fix-crash-empty-pile.patch

 -- Olivier Gayot <email address hidden> Fri, 22 Mar 2024 14:59:22 +0100