develop does not support placing the egg outside of the source folder

Originally reported by: dirk-thomas (Bitbucket: dirk-thomas, GitHub: dirk-thomas)

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When passing egg_info --egg-base SOMEPATH additionally to setup.py develop the egg file is created in that location. This is done to build out-of-source and not drop any artifacts in the source folder of the package.

But it always fails with the following exception: https://bitbucket.org/pypa/setuptools/src/18eceee63709bc70c06b51a609f3dbd2eab07ef4/setuptools/command/develop.py?at=default#cl-84

It seems like there is no way to parameterize the invocation with --build-directory, --egg-path which would be valid.

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• Bitbucket: https://bitbucket.org/pypa/setuptools/issue/361

[cjerdonek]

What would be the intended setup.py develop invocation to support putting the egg file / egg-info directory in a different location? I don't see an --egg-base option for develop when running python setup.py develop --help. I only see an --egg-path option, which looks slightly different.

[dhood]

@dirk-thomas fyi

[dirk-thomas]

The idea of running develop wihtout putting any files into the source path of the package is similar to "out-of-source builds" with other build system (e.g. CMake). I would prefer not to place anything in the source path of the package but instead specify a build folder (out of source) where all necessary temporary / build files are being created. An out of source build comes with the usual advantages: multiple build directories with different setups, no need to babysit generated files, easy to clean, etc.

[cjerdonek]

Another use case (the one I'm interested in) would help with a local development workflow using Docker. Say you install your package inside a Dockerfile in "develop" mode, and you set things up so that as you edit files on your local machine, the files get synced into the Docker container using a volume. Putting the build artifacts outside of the source directory would ensure they don't get overwritten when the volume is mounted. Otherwise, you have to do something like re-run setup.py develop after the volume is mounted, or do contortions involving temporarily moving the build artifacts prior, etc.