ncols Out of bounds error for GridSpec with fixed ncols when adding rows only.

[MarcSkovMadsen]

I'm on Panel 0.10.0

If I run pytest on the below

import panel as pn

def test_gridspec_ncols():
    grid = pn.layout.GridSpec(ncols=3)
    for index in range(0,5):
        grid[index,:]=pn.pane.Markdown("Hello World")

$ pytest 'scripts\test_gridspec.py'
Test session starts (platform: win32, Python 3.7.6, pytest 5.4.2, pytest-sugar 0.9.3)
rootdir: C:\repos\private\awesome-panel, inifile: pytest.ini
plugins: cov-2.8.1, mock-3.1.0, sugar-0.9.3
collecting ... 

――――――――――――――――――――――――――― test_gridspec_ncols ――――――――――――――――――――――――――――

    def test_gridspec_ncols():
        grid = pn.layout.GridSpec(ncols=3)
        for index in range(0,5):
>           grid[index,:]=pn.pane.Markdown("Hello World")

scripts\test_gridspec.py:6:
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

self = GridSpec(ncols=3, nrows=4)
    [0] Markdown(str)
    [1] Markdown(str)
    [2] Markdown(str)
    [3] Markdown(str)
index = (4, slice(None, None, None)), obj = Markdown(str)

    def __setitem__(self, index, obj):
        from ..pane.base import panel
        if not isinstance(index, tuple):
            raise IndexError('Must supply a 2D index for GridSpec assignment.')

        yidx, xidx = index
        if isinstance(xidx, slice):
            x0, x1 = (xidx.start, xidx.stop)
        else:
            x0, x1 = (xidx, xidx+1)

        if isinstance(yidx, slice):
            y0, y1 = (yidx.start, yidx.stop)
        else:
            y0, y1 = (yidx, yidx+1)

        l = 0 if x0 is None else x0
        r = self.nrows if x1 is None else x1
        t = 0 if y0 is None else y0
        b = self.ncols if y1 is None else y1

        if self._cols_fixed and (l >= self.ncols or r > self.ncols):
>           raise IndexError('Assigned object to column(s) out-of-bounds '
                             'of the grid declared by `ncols`. which '
                             f'was set to {self.ncols}.')
E           IndexError: Assigned object to column(s) out-of-bounds of the grid declared by `ncols`. which was set to 3.

.venv\lib\site-packages\panel\layout\grid.py:416: IndexError

 scripts/test_gridspec.py ⨯                                   100% ██████████
========================= short test summary info ==========================
FAILED scripts/test_gridspec.py::test_gridspec_ncols - IndexError: Assigne...

Results (1.47s):
       1 failed
         - scripts/test_gridspec.py:3 test_gridspec_ncols

I would expect to be able to add any number of rows. I only set a limit on the number of columns.

Additional Context

I use a similar script on awesome-panel.org to convert from a ListLike specification of panels to a GridSpec such that I can use all templates together on awesome-panel.org.

[hoxbro]

I think the problem is related to r and b. If i change the lines above the IndexError to the following, I can run the code.

 l = 0 if x0 is None else x0
 r = self.ncols if x1 is None else x1
 t = 0 if y0 is None else y0
 b = self.nrows if y1 is None else y1

I have a hard time figure out how the naming works, it would be nice with a docstring telling what the names means.
But for me it make sense that r should be related to self.ncols when I look at the if-statement and the same for b and self.nrows.

If I have understood it correct, I can make a PR for it. :)

[philippjfr]

Sorry I'm so used to lbrt being abbreviations for left, bottom, right, top of a bounding box that I didn't think about leaving docstrings.

[hoxbro]

That make sense. Properly just me who didn't knew that...

Should I make a PR for this?