Editable pip install is not working correctly

[maarten-ic]

When following these instructions on the documentation, the package is installed through pip install -e .[dev].

Unfortunately, editable installs are not supported with a custom pkg_dir in setup.py. See for instance this ticket: pypa/pip#3160
Eventually you'll get ModuleNotFoundErrors like below:

$ muscle_manager --help
Traceback (most recent call last):
  File "/home/[...]/venv_muscle3/bin/muscle_manager", line 33, in <module>
    sys.exit(load_entry_point('muscle3', 'console_scripts', 'muscle_manager')())
  File "/home/[...]/venv_muscle3/bin/muscle_manager", line 25, in importlib_load_entry_point
    return next(matches).load()
  File "/usr/lib/python3.8/importlib/metadata.py", line 77, in load
    module = import_module(match.group('module'))
  File "/usr/lib/python3.8/importlib/__init__.py", line 127, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1014, in _gcd_import
  File "<frozen importlib._bootstrap>", line 991, in _find_and_load
  File "<frozen importlib._bootstrap>", line 975, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 671, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 848, in exec_module
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "/home/[...]/projects/muscle3/muscle3/muscle_manager.py", line 10, in <module>
    from libmuscle.manager.manager import Manager
ModuleNotFoundError: No module named 'libmuscle.manager'

Suggested immediate fix: update documentation to not use pip install -e.

If I have better suggestions I'll update this issue.

[DaanVanVugt]

Relevant discussion at pypa/setuptools#230

[DaanVanVugt]

Adding the --use-pep517 flag to get pip install --use-pep517 -e .[dev] resolves the problem. I believe PEP517 is enabled by default when using pyproject.toml, so at that point the flag can be removed again.