Cannot update main when main is GridSpec #1741
Description
ALL software version info
Panel MASTER branch
Description of expected behavior and the observed behavior
When the template main is a GridSpec I would expect to be able to update the GridSpec.
For example at awesome-panel.org I was trying to prepopulate a Template across pages to get a shared look and feel. But a few pages should look different and replace one or more of the prepopulated items.
Complete, minimal, self-contained example code that reproduces the issue
from panel.template import ReactTemplate
from panel.pane import Markdown
def test_grid_spec_replace():
template=ReactTemplate()
first = Markdown("I was here first")
template.main[0,0]=first
second=Markdown("But now I take over")
template.main[0,0]=second
return template
test_grid_spec_replace().servable()
Stack traceback and/or browser JavaScript console output
$ 2020-11-04 06:21:39,386 Starting Bokeh server version 2.2.3 (running on Tornado 6.0.4)
2020-11-04 06:21:39,387 User authentication hooks NOT provided (default user enabled)
2020-11-04 06:21:39,390 Bokeh app running at: http://localhost:5006/script
2020-11-04 06:21:39,391 Starting Bokeh server with process id: 21168
WARNING:param.GridSpec00005: Specified region overlaps with the following existing object(s) in the grid:
(0, 0): Markdown(str)
The following shows a view of the grid (empty: 0, occupied: 1, overlapping: 2):
[[2 0 0 0 0 0 0 0 0 0 0 0]]
2020-11-04 06:21:47,318 Specified region overlaps with the following existing object(s) in the grid:
(0, 0): Markdown(str)
The following shows a view of the grid (empty: 0, occupied: 1, overlapping: 2):
[[2 0 0 0 0 0 0 0 0 0 0 0]]
2020-11-04 06:21:47,636 WebSocket connection opened
2020-11-04 06:21:47,637 ServerConnection createdScreenshots or screencasts of the bug in action
Additional Context
I simply don't understand why the changes to the different parameters of a BasicTemplate needs to trigger complicated updates. I believe instead that there should be one function to update and render the template when needed. That would be much easier. I also think the current implementation has a performance cost because there will potentially be a lot of complicated updates that could have been simplified to one.
