New wrapper for flags

[Paebbels]

This PR proposes a solution to get rid of flags_name.value = True syntax and uses proper descriptor protocols for hiding the C-binding wrapper.

Old:

Flags_Gather_Comments.value = True

New:

Flags().Gather_Comments = True

@tgingold if you like the idea, I would do these additional steps:

• Eliminate the parenthesis (instantiating a singleton):

  Flags.Gather_Comments = True

• Expand this technique to other flags too. E.g. in parse, vhdl, ...

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Originally started PR was #2105.

[tgingold]

I'd really prefer to have a layered approach. libghdl should be just a ctype interface, and a more pythonic interface would be implemented on top of it.

Could you at least keep the wrappers as globals in flags.py ? That would also keep backward compatibility.
Than I am OK for the Flags class.

[Paebbels]

With my proposal, I would like to enhance what ctypes doesn't do well. They have implemented a descriptor interface, but introduced another level of value access by using .value syntax.

Could you at least keep the wrappers as globals in flags.py

I didn't fully get this point.
Do you mean:

• keeping the old ctypes wrappers in parallel to the Flags class, OR
• providing aliases to the descriptors, so old names still work?

My goal is to provide a clean and easy syntax for bare variables from libghdl, which ctype doesn't provide. No further overhead or abstraction is planned on pyGHDL.libghdl.

I'll do further improvements like getting rid of the () and then you can see a more final proposal.

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In an ideal world, I wouldn't implement this using a singletone + (instance) properties / descriptors. I would prefer to use class properties (like @Property + @classmethod). Unfortunately, this feature is broken in Python and it's even a vulnerability. I'm trying to push on fixing it in Python itself. If so, it won't be available before 3.12 as I don't expect back porting.

[tgingold]

With my proposal, I would like to enhance what ctypes doesn't do well. They have implemented a descriptor interface, but introduced another level of value access by using .value syntax.

I think I perfectly understand your proposal and I think this is a good idea.

Could you at least keep the wrappers as globals in flags.py I didn't fully get this point. Do you mean: • keeping the old ctypes wrappers in parallel to the Flags class, OR • providing aliases to the descriptors, so old names still work?

I would simply keep the wrappers as they are and just add the Flags() class. No need to move the wrappers inside the class. And yes, I agree that getting rid of the () would also be nice!

[umarcor]

@Paebbels, can this be rebased and merged or does it need additional work?

[Paebbels]

I can rebase, but there is additional work needed from my side.