Highlight an issue(?) with egg_info.writers in setuptools.setup. I have 3 packages:

• writer, which has one method that writes an output.txt file
• writing, which uses writer to write an output.txt file to it's EGG-INFO directory
  • More on that can be found here
• innocent, which has nothing to do with the two other packages.

The issue: if you install writer, writing, and then innocent in that order, writer:write is run as part of the install process for innocent, giving it an output.txt file.

To me, this seems like an error, or at least a confusing behavior. I wouldn't expect this to apply to all future python package installs, and could easily see it causing issues if:

• Some later application checked these egg-info/ directories, and the presence of this new file meant something.
• The egg_info.writers function performed some action coupled to the package itself, causing installs of other packages to error.

Reproduce

docker-compose up --build; docker-compose rm

will run an ls inside the "innocent" package's egg-info directory, showing the confusingly written output.txt file.

Workaround

Check out the workaround package to see a way to get egg_info.writers to behave like I'd expect.