Attribute assignment safeguards for NestModule and SynapseCollection

[Helveg]

• Settings unknown attributes on nest module raises an AttributError
• Fixed an always-true condition that allowed setting unknown attributes on SynapseCollection.

Closes #2219.

Just 1 remark: while the network or synapse collection is empty, you can set unknown attributes. Any idea why this was implemented, should it remain that way?

[heplesser]

@Helveg Thanks!

• This change seems too drastic, all Pynest tests seem to fail now ;).
• How does this address the problem that unknown synapse collection objects are not detected?
• Please add a regression test, both for kernel and synapse attributes.

[heplesser]

Just 1 remark: while the network or synapse collection is empty, you can set unknown attributes. Any idea why this was implemented, should it remain that way?

I cannot think of any reason for this behavior. One technical aspect might be that the detection of unknown parameter names for node collections largely happens in SetStatus() in the kernel, and for an empty collection we have nothing to call that on. @stinebuu @hakonsbm Any comments?

[Helveg]

How does this address the problem that unknown synapse collection objects are not detected?

Where can I find a description of this problem? I thought the problems were related to attribute assignment on nest and SynapseCollection?

[heplesser]

How does this address the problem that unknown synapse collection objects are not detected?

Where can I find a description of this problem? I thought the problems were related to attribute assignment on nest and SynapseCollection?

Sorry, my comment was unclear. What I meant is: How does this change ensure that

c = nest.GetConnections()
c.gewicht = 10

will raise an exception because gewicht is not a known synapse parameters. It should have been "parameter" or "attribute", not "object" in my original question.

[Helveg]

There already was a __setattr__ implementation that defers to SynapseCollection.set, which goes into SLI and errors graciously if the key isn't known, it just wasn't being called. The problem was that the condition to defer to .set was always false, and instead super().__setattr__(attr, value) was always called which would just set the attribute the regular Python way. You can see in e87ae1c how I remedied that.

[heplesser]

@Helveg Thanks for the fixes! Could you improve comments a little, see inline remarks?

[hakonsbm]

Just 1 remark: while the network or synapse collection is empty, you can set unknown attributes. Any idea why this was implemented, should it remain that way?

I cannot think of any reason for this behavior. One technical aspect might be that the detection of unknown parameter names for node collections largely happens in SetStatus() in the kernel, and for an empty collection we have nothing to call that on. @stinebuu @hakonsbm Any comments?

@heplesser Yes, but the behaviour isn't consistent for NodeCollections and SynapseCollections.

For empty NodeCollections, trying to get a non-existent attribute results in an AttributeError, while trying to set an attribute will just return None without setting anything.

An empty SynapseCollection will return an empty tuple when trying to get an unknown attribute, while setting an attribute will set the attribute on the SynapseCollection itself. Interestingly, setting a valid attribute, like weight, on a non-empty SynapseCollection will also set it as an attribute of the SynapseCollection, not as a property of the connections.

[stinebuu]

This looks good to me, I only have a small comment on a comment.

Regarding the different behavior for NodeCollection and SynapseCollection, I cannot remember why there is a difference. Maybe something we should look at further in another issue?

[stinebuu]

👍

[jougs]

@Helveg: The merge of this PR leads to the following error on Read the Docs.

Traceback (most recent call last):
  File "/home/docs/checkouts/readthedocs.org/user_builds/nest-simulator/envs/latest/lib/python3.8/site-packages/sphinx/cmd/build.py", line 276, in build_main
    app = Sphinx(args.sourcedir, args.confdir, args.outputdir,
  File "/home/docs/checkouts/readthedocs.org/user_builds/nest-simulator/envs/latest/lib/python3.8/site-packages/sphinx/application.py", line 216, in __init__
    self.config = Config.read(self.confdir, confoverrides or {}, self.tags)
  File "/home/docs/checkouts/readthedocs.org/user_builds/nest-simulator/envs/latest/lib/python3.8/site-packages/sphinx/config.py", line 173, in read
    namespace = eval_config_file(filename, tags)
  File "/home/docs/checkouts/readthedocs.org/user_builds/nest-simulator/envs/latest/lib/python3.8/site-packages/sphinx/config.py", line 342, in eval_config_file
    raise ConfigError(msg % traceback.format_exc()) from exc
sphinx.errors.ConfigError: There is a programmable error in your configuration file:

Traceback (most recent call last):
  File "/home/docs/checkouts/readthedocs.org/user_builds/nest-simulator/envs/latest/lib/python3.8/site-packages/sphinx/config.py", line 329, in eval_config_file
    exec(code, namespace)
  File "/home/docs/checkouts/readthedocs.org/user_builds/nest-simulator/checkouts/latest/doc/userdoc/conf.py", line 86, in <module>
    nest.NestModule = type(nest)
  File "/home/docs/checkouts/readthedocs.org/user_builds/nest-simulator/checkouts/latest/pynest/nest/__init__.py", line 423, in _setattr_error
    raise err from None
AttributeError: can't set attribute 'NestModule' on module 'nest'

@steffengraber, @jessica-mitchell, @terhorstd

[terhorstd]

This breaks the documentation generation: https://readthedocs.org/api/v2/build/15469804.txt
We're looking into it.

[terhorstd]

This was also one of the Python trickery nest.NestModule = type(nest) in Sphinx's conf.py, that is now not possible anymore. Where would this best to be fixed? Here or in conf.py?

[Helveg]

1. Check if the trickery is still required, the line may just be removed (check if the KernelAttribute doc page is still generated correctly)
2. Change it to vars(nest)["NestModule"] = type(nest)