ORM: Fix typing of aiida.orm.nodes.data.code module

[sphuber]

Fixes #5819

[chrisjsewell]

Heya, so as I've mentioned before, the problem with using pathlib.PurePath here, is that it implies that one can also represent paths on Windows (aka DOS) systems, and I don't believe that is the case.

For starters, I don't think SshTransport is compatible with the remote computer being a Windows machine anyway.

Then for the code:

1. Since aiida can only be installed on UNIX, this means that pathlib.PurePath will actually always be pathlib.PurePosixPath.
2. Since the path is serialised to the storage as a string, even if the user would specifically add the executable path as PureWindowsPath, it would still end up being read as a unix path, e.g. PurePath(str(PureWindowsPath(r'C:\path\to\exec.exe'))).parent -> PurePosixPath('.') which is obviously wrong.
   • if you actually wantd to allow for windows paths, then you would need to specifically serialise the path somehow with specific information on the OS

So, basically, I think you should change all the PurePath uses to PurePosixPath

[sphuber]

But what you are describing is a limitation of the Transport interface and the limitations other parts of AiiDA impose on the remote computer. But in principle the Code is abstract in that sense and should be able to support both no? It is possible that we implement support in the future for running on remote windows computers, and in that case the code classes should just work with PurePath. Is there any downside to keeping PurePath now?

The only thing maybe is if a user runs AiiDA on a windows machine (is this even possible?) uses pathlib.Path to construct the code instance and so (unwittingly) uses the wrong path type for a remote computer that is going to be POSIX-like. Still, since I don't think we support Windows, this shouldn't be an actual possibility.

[chrisjsewell]

The Code.executable_path is currently stored in the database as a string.
How do you know whether that string is intended to be posix or windows?
Currently it is essentially interpreted as the same as the filesystem that aiida is installed on, which is wrong.

[chrisjsewell]

At present the problem is, by wrapping things in pathlib objects you have essentially made the Code less abstract than it previously was.

[sphuber]

Currently it is essentially interpreted as the same as the filesystem that aiida is installed on, which is wrong.

Ah I see now, yeah you are right, that is a problem.

[chrisjsewell]

cheers