FIX Improve robustness of attribute query for JSProxy

[mvdoc]

Functions like code.export.plot_panels fail from time to time in an unpredictable way. It looks like the culprit is that the JSProxy object tries to get some attributes that do not exist yet (see #449). However, when inspecting the JavaScript console, those attributes do exist. This suggests that the querying process is not robust enough to random delays in updating the viewer/JS environment.

This PR adds a simple logic that queries for the desired attr up to 10s before giving up. It should make the querying process a bit more robust.

Closes #449 (hopefully for good)

[TomDLT]

I don't quite understand why accessing self.attrs starts a query.

But the PR looks good to me.

(Failing tests are unrelated. They are due to a deprecated function in nibabel 4.0.)

[mvdoc]

From my reading of the code, JSProxy.__getattr__ implements a special case for JSProxy.attrs, which runs self.send(method='query', params=[self.name])[0]. So every time self.attrs is accessed, a query is sent. This should be fine if, once an attribute is present in self.attrs, subsequent calls to self.attrs still contain that attribute. But I'm not sure this is the case (and some random failures indicated that it wasn't), so I wanted to be careful.

pycortex/cortex/webgl/serve.py

Lines 324 to 334 in 908cc80

	def __getattr__(self, attr):
	if attr == 'attrs':
	return self.send(method='query', params=[self.name])[0]
	if attr not in self.attrs:
	raise KeyError(f"Attribute '{attr}' not found in {self}")
	if self.attrs[attr][0] in ["object", "function"]:
	return JSProxy(self.send, "%s.%s"%(self.name, attr))
	else:
	return self.attrs[attr][1]

[TomDLT]

From my reading of the code, JSProxy.__getattr__ implements a special case for JSProxy.attrs.

Oh right, I missed that for some reason, thanks!

[mvdoc]

Unfortunately, the viewer still crashes from time to time. It seems to me that 10s should be enough time to wait, so maybe the problem is somewhere else. :\

[TomDLT]

Does it crash after the 10sec wait?

[mvdoc]

Yep, it crashes with the same error: (Attribute 'surface' not found in <JS: window.viewer.ui>)...

[mvdoc]

This new change I implemented seems to have solved the problem (🤞). I made a new property for JSProxy.attrs in case there is some problem with calling __getattr__ recursively in an async setup like we the one we have with tornado and JS. This change also helped me figure out that sometimes querying window.viewer can return None or an int (an error number?), probably when the JS viewer hasn't been updated.