setup.py: Make click dependency optional

[jonte]

This makes it easier to install only the python modules, and not the w1thermsensor command line utility.

If there is only interest in the python modules, do the following:

pip install w1thermsensor

If the w1thermsensor utility is invoked when the package has been installed in this way, an informative error message is displayed, notifying that click needs to be installed.

To ensure that the w1thermsor utility also works, specify additional dependencies using [CLI], as such:

pip install w1thermsensor[CLI]

Signed-off-by: Jonatan Pålsson jonatan.p@gmail.com

[codecov-io]

Codecov Report

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[jonte]

There are two issues with this, as I see it now:

• Even when [CLI] is not specified, setup.py will install w1thermsensor - I couldn't figure out how to disable this. It might be nicer if it is not installed at all.
• I don't know which minimum version of click we support. I arbitrarily chose 7, which is quite recent.

What do you think @timofurrer ?

[jonte]

Perhaps some background information is in place as well.. I wish to install this module in my Yocto build, but I do not use the w1thermsensor utility. In my BitBake recipe, I will make the w1thermsensor utility a separate package, which can be optionally selected by users of the BitBake recipe.. This means that the utility must also be optional when building w1thermsensor itself.

An altenative way to solve this would be to patch w1thermsensor in the BitBake recipe in order to make the command line utility optional, but I would rather have that feature upstream (here :)) if possible.

[timofurrer]

Not sure what setuptools and pip support regarding those extras for entry_points. According to https://packaging.python.org/specifications/entry-points/#data-model this should actually be supported, but is no longer recommended.

However, I don't really understand why and am not sure what a successor of this should be. I'd consider this feature as useful.

Did you get any further? @jonte

[jonte]

Hi,

I didn't really get further unfortunately. I asked on the Distutils-SIG ML a few months back, and got this reply:

I would like to change the behavior, so that the entry point is not installed if the extra dependencies are not available (and perhaps also show a warning, indicating that this entry point has not been installed).

I don't believe this is possible. Achieving this new behavior would, at a minimum, require changes to pip (and possibly also to the entry points format in order to indicate which behavior is desired). As associating extras with entry points is currently considered deprecated to begin with, I doubt you'd have much luck convincing the pip maintainers to add such a feature.

The closest way to get the behavior you want would be to split off the CLI-specific code from your project into a separate project, and have this new project install the entry point while always depending on the first project and the "CLI" extras.

The last paragraph hints towards a workaround. I did not try this yet though.

[timofurrer]

That really sounds unfortunate for our use case here ...

The closest way to get the behavior you want would be to split off the CLI-specific code from your project into a separate project, and have this new project install the entry point while always depending on the first project and the "CLI" extras.

I doubt that this is going to happen for w1thermsensor. It would add an overhead which really is undesired. If a distribution wants to split CLI and Python API into different packages they are free to do so.

If the Python packaging situation changes, I'm happy to tackle this again - for now, I'm going to close this :tada: