new component element and hot-reloading

[jamesdbrock]

The new @component elements don't work with hot reloading.

Encountered exception while reloading: Error while reloading <MyApp id=0x7fffdbac48e0  />: New class expects prop (args) not present in old class
Traceback (most recent call last):
  File "/home/jbrock/work/oth/pyedifice/pyedifice/edifice/app.py", line 157, in event
    render_result = self._render_engine._refresh_by_class(classes)
  File "/home/jbrock/work/oth/pyedifice/pyedifice/edifice/engine.py", line 451, in _refresh_by_class
    raise ValueError(
Stemming from these renders:
ValueError: Error while reloading <MyApp id=0x7fffdbac48e0  />: New class expects prop (args) not present in old class

I think it has something to do with this.

pyedifice/edifice/_component.py

Lines 660 to 665 in 14ba471

	def __init__(self, *args: P.args, **kwargs: P.kwargs):
	name_to_val = defaults.copy()
	name_to_val.update(filter(not_ignored, zip(varnames, args, strict=False)))
	name_to_val.update(((k, v) for (k, v) in kwargs.items() if k[0] != "_"))
	name_to_val["children"] = name_to_val.get("children") or []
	self._register_props(name_to_val)

[jamesdbrock]

To see hot reloading succeed and fail, check out branch hotreload1 which restores the old example tutorial program.

Hot reloading works:

python -m edifice examples/tutorial.py MyApp

Hot reloading doesn't work:

python -m edifice examples/tutorial_old.py MyApp

[considerate]

My immediate thought is that this might be related to the children prop

[jamesdbrock]

When hot reloading the new tutorial.py on this line

pyedifice/edifice/engine.py

Line 444 in 14ba471

kwargs = {k: old_comp.props[k] for k, v in parameters[1:]

We have

old_comp.props = PropsDict({'children': []})

and

parameters = [
0: ('self', <Parameter "self">)
1: ('args', <Parameter "*args: P.args">)
2: ('kwargs', <Parameter "**kwargs...P.kwargs">)

So we get Exception has occurred: KeyError 'args'.

When hot reloading the tutorial_old.py on that line

parameters = [('self', <Parameter "self">)]

[jamesdbrock]

This is the hard part. We must somehow construct a new Element, using the required constructor arguments, which are the kwargs props. It doesn't have to be the right props, because we can just assign the right props on the next line after the Element is constructed. But constructing it is tricky.

pyedifice/edifice/engine.py

Line 455 in 14ba471

parts[3] = new_comp_class(**kwargs)