In run(), there is a warning message printed to the console if warn_dir is '1':
  if self.warn_dir:
    self.warn("setup script did not provide a directory for "
              "'%s' -- installing right in '%s'" %
             (f, self.install_dir))

warn_dir should be unset in run to suppress the warning if an install_dir is specified.

Does this cause a warning to be printed out when it should not?  Or did you find this by reading the code?

[I think I remember this code being changed in the (now defunct) distutils2 project.]

The former. I copy/pasted the code block to show from where the warning message was being printed.

Can you give us steps to reproduce the issue?

I don't have access to the code anymore that repro'ed this issue. I just remember writing a setup script for a module I was working on, and when 'install' was run, it would print this error message.

It's pretty easy to see in code what the problem is though. In install_data.py, warn_dir is set to '1' in initialize_options(), but it's value is never altered. So regardless of what is or isn't passed in, the warning will always be printed.

Distutils is now deprecated (see PEP 632) and all tagged issues are being closed. From now until removal, only release blocking issues will be considered for distutils.

If this issue does not relate to distutils, please remove the component and reopen it. If you believe it still requires a fix, most likely the issue should be re-reported at https://github.com/pypa/setuptools