GridSpec objects attribute violates Panel interface contract

[analog-cbarber]

The Panel class provides an objects attribute that is expected to contain a list of child objects:

class Panel(Reactive):
   ...
    objects = param.Parameter(default=[], doc="""
        The list of child objects that make up the layout.""")

but GridSpec overrides this with a dictionary:

class GridSpec(Panel):
   ...
    objects = param.Dict(default={}, doc="""
        The dictionary of child objects that make up the grid.""")

Consequently any code that is meant to operate on a Panel .object list is likely to break when applied to a GridSpec. In particular, the Panel._cleanup, which is inherited by GridSpec will fail because iterating over the objects will return tuples instead of the actual child objects.

For this case, you could probably fix this by overriding _cleanup in GridSpec but it would not fix the underlying issue.

Observed using Panel 0.6.0.

[philippjfr]

Thanks, most of the code in Panel should probably just move to ListPanel.

[analog-cbarber]

Seems like this is might not be a good first issue if it involves a significant API change.