Allow optional compilation of C extensions

[teknico]

• I have searched the issues of this repo and believe that this is not a duplicate.
• I have searched the documentation and believe that my question is not covered.

This issue is prompted by a suggestion:

I'd recommend creating a new issue detailing shortcomings of the current implementations with as much details as possible please.

Feature Request

This is in reference to issue #11. The tinydecred project uses Poetry, and we're trying to add a Cython-generated extension to speed up the code in one of the Python files, using the undocumented feature mentioned in issue #11.

Here's the build.py file we're using:

try:
    from Cython.Build import cythonize
except ImportError:
    def build(setup_kwargs):
        pass
else:
    def build(setup_kwargs):
        setup_kwargs.update(
            {"ext_modules": cythonize(["decred/crypto/secp256k1/field.py"])}
        )

A problem we have is that we'd like to ignore the error that happens if the developer does not have a C compiler installed and they execute the poetry install command (example).

(Ignoring such errors is the correct behavior in this case because the C extension is generated by Cython from a Python file and a matching .pxd file. If the compiled dynamic library is not there, the interpreter will just use the Python file.)

Thanks.

[abn]

If this is the desired behaviour, wouldn't it be cleaner and more explicit to wrap the build step in a try catch within the build.py?

[teknico]

Indeed, and that's what we ended up doing.

Still a workaround though, so we'll be happy to eventually see official support of non-Python extensions in Poetry.

[abn]

Fair enough. Within the frame of current implementation, I'd consider that the solution for now.

That said, we should consider this if we end up further integrating support for C extensions.

[Secrus]

Closing as duplicate of #1351

[github-actions]

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