Running pep517.build (only with setuptools?) on PyPy does not fetch the backend / fails with BackendUnavailable

[Julian]

Full reproducer:

somepython=pypy
rm -rf venv pep517-venv foo && \
"$somepython" ~/Development/virtualenv/virtualenv.py --quiet venv && \
venv/bin/python -m pip install --quiet mkpkg && \
venv/bin/mkpkg foo && \
venv/bin/python ~/Development/virtualenv/virtualenv.py --no-setuptools pep517-venv && \
pep517-venv/bin/python -m pip install --quiet pep517 && \
pep517-venv/bin/python -m pep517.build foo

fails with:

  No LICENSE.txt / LICENSE found in source
/Users/julian/Desktop/venv/site-packages/pip/_vendor/msgpack/fallback.py:133: DeprecationWarning: encoding is deprecated, Use raw=False instead.
  unpacker = Unpacker(None, max_buffer_size=len(packed), **kwargs)
Set up CI at: https://travis-ci.com/Julian/foo
Using real prefix '/usr/local/Cellar/pypy/7.2.0/libexec'
  No LICENSE.txt / LICENSE found in source
Path not in prefix '/Users/julian/Desktop/venv/include' '/usr/local/Cellar/pypy/7.2.0/libexec'
New pypy executable in /Users/julian/Desktop/pep517-venv/bin/python
Also creating executable in /Users/julian/Desktop/pep517-venv/bin/pypy
Installing pip, wheel...
done.
/Users/julian/Desktop/pep517-venv/site-packages/pip/_vendor/msgpack/fallback.py:133: DeprecationWarning: encoding is deprecated, Use raw=False instead.
  unpacker = Unpacker(None, max_buffer_size=len(packed), **kwargs)
No handlers could be found for logger "pep517.envbuild"
Traceback (most recent call last):
  File "/usr/local/Cellar/pypy/7.2.0/libexec/lib-python/2.7/runpy.py", line 174, in _run_module_as_main
    "__main__", fname, loader, pkg_name)
  File "/usr/local/Cellar/pypy/7.2.0/libexec/lib-python/2.7/runpy.py", line 72, in _run_code
    exec code in run_globals
  File "/Users/julian/Desktop/pep517-venv/site-packages/pep517/build.py", line 124, in <module>
    main(parser.parse_args())
  File "/Users/julian/Desktop/pep517-venv/site-packages/pep517/build.py", line 120, in main
    build(args.source_dir, dist, args.out_dir)
  File "/Users/julian/Desktop/pep517-venv/site-packages/pep517/build.py", line 88, in build
    _do_build(hooks, env, dist, dest)
  File "/Users/julian/Desktop/pep517-venv/site-packages/pep517/build.py", line 61, in _do_build
    reqs = get_requires({})
  File "/Users/julian/Desktop/pep517-venv/site-packages/pep517/wrappers.py", line 213, in get_requires_for_build_sdist
    'config_settings': config_settings
  File "/Users/julian/Desktop/pep517-venv/site-packages/pep517/wrappers.py", line 265, in _call_hook
    raise BackendUnavailable(data.get('traceback', ''))
BackendUnavailable

which seems to only fail on PyPy, because on CPython changing somepython=python3.6 and rerunning seems to succeed.

For ease, the (generated) pyproject.toml in that stub package is:

[build-system]
requires = [
    # The minimum setuptools version is specific to the PEP 517 backend,
    # and may be stricter than the version required in `setup.py`
    "setuptools>=40.6.0",
    "setuptools_scm",
    "wheel",
]
build-backend = "setuptools.build_meta"

[Julian]

(In case anyone else encounters this in the meanwhile, manually installing the build deps fixes it, see this commit and its GitHub Action run for example).

[oberstet]

also running into this. howeever, even after doing pip install -U setuptools setuptools-scm pip wheel, I am still running into:

Collecting crossbar
  Cloning https://github.com/crossbario/crossbar.git (to revision master) to /tmp/pip-install-0bk26s3h/crossbar
  Running command git clone -q https://github.com/crossbario/crossbar.git /tmp/pip-install-0bk26s3h/crossbar
  Installing build dependencies ... done
  Getting requirements to build wheel ... done
ERROR: Exception:
Traceback (most recent call last):
  File "/home/oberstet/pypy36_1/site-packages/pip/_internal/cli/base_command.py", line 153, in _main
    status = self.run(options, args)
  File "/home/oberstet/pypy36_1/site-packages/pip/_internal/commands/install.py", line 382, in run
    resolver.resolve(requirement_set)
  File "/home/oberstet/pypy36_1/site-packages/pip/_internal/legacy_resolve.py", line 201, in resolve
    self._resolve_one(requirement_set, req)
  File "/home/oberstet/pypy36_1/site-packages/pip/_internal/legacy_resolve.py", line 365, in _resolve_one
    abstract_dist = self._get_abstract_dist_for(req_to_install)
  File "/home/oberstet/pypy36_1/site-packages/pip/_internal/legacy_resolve.py", line 313, in _get_abstract_dist_for
    req, self.session, self.finder, self.require_hashes
  File "/home/oberstet/pypy36_1/site-packages/pip/_internal/operations/prepare.py", line 224, in prepare_linked_requirement
    req, self.req_tracker, finder, self.build_isolation,
  File "/home/oberstet/pypy36_1/site-packages/pip/_internal/operations/prepare.py", line 49, in _get_prepared_distribution
    abstract_dist.prepare_distribution_metadata(finder, build_isolation)
  File "/home/oberstet/pypy36_1/site-packages/pip/_internal/distributions/source/legacy.py", line 37, in prepare_distribution_metadata
    self._setup_isolation(finder)
  File "/home/oberstet/pypy36_1/site-packages/pip/_internal/distributions/source/legacy.py", line 90, in _setup_isolation
    reqs = backend.get_requires_for_build_wheel()
  File "/home/oberstet/pypy36_1/site-packages/pip/_vendor/pep517/wrappers.py", line 152, in get_requires_for_build_wheel
    'config_settings': config_settings
  File "/home/oberstet/pypy36_1/site-packages/pip/_vendor/pep517/wrappers.py", line 255, in _call_hook
    raise BackendUnavailable(data.get('traceback', ''))
pip._vendor.pep517.wrappers.BackendUnavailable: Traceback (most recent call last):
  File "/home/oberstet/pypy36_1/site-packages/pip/_vendor/pep517/_in_process.py", line 63, in _build_backend
    obj = import_module(mod_path)
  File "/home/oberstet/pypy3.6-v7.3.0-linux64/lib-python/3/importlib/__init__.py", line 126, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1003, in _gcd_import
  File "<frozen importlib._bootstrap>", line 980, in _find_and_load
  File "<frozen importlib._bootstrap>", line 950, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 228, in _call_with_frames_removed
  File "<frozen importlib._bootstrap>", line 1003, in _gcd_import
  File "<frozen importlib._bootstrap>", line 980, in _find_and_load
  File "<frozen importlib._bootstrap>", line 964, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 674, in _load_unlocked
  File "<builtin>/frozen importlib._bootstrap_external", line 691, in exec_module
  File "<frozen importlib._bootstrap>", line 228, in _call_with_frames_removed
  File "/tmp/pip-build-env-y2_d_h9p/overlay/site-packages/setuptools/__init__.py", line 18, in <module>
    import setuptools.version
  File "/tmp/pip-build-env-y2_d_h9p/overlay/site-packages/setuptools/version.py", line 1, in <module>
    import pkg_resources
  File "/tmp/pip-build-env-y2_d_h9p/overlay/site-packages/pkg_resources/__init__.py", line 36, in <module>
    import email.parser
  File "/home/oberstet/pypy3.6-v7.3.0-linux64/lib-python/3/email/parser.py", line 12, in <module>
    from email.feedparser import FeedParser, BytesFeedParser
  File "/home/oberstet/pypy3.6-v7.3.0-linux64/lib-python/3/email/feedparser.py", line 27, in <module>
    from email._policybase import compat32
  File "/home/oberstet/pypy3.6-v7.3.0-linux64/lib-python/3/email/_policybase.py", line 9, in <module>
    from email.utils import _has_surrogates
  File "/home/oberstet/pypy3.6-v7.3.0-linux64/lib-python/3/email/utils.py", line 28, in <module>
    import random
  File "/home/oberstet/pypy3.6-v7.3.0-linux64/lib-python/3/random.py", line 46, in <module>
    from hashlib import sha512 as _sha512
ImportError: cannot import name 'sha512'

Makefile:188: recipe for target 'install' failed
make: *** [install] Error 2

but this works

(pypy36_1) oberstet@intel-nuci7:~/scm/crossbario/crossbarfx$ which python
/home/oberstet/pypy36_1/bin/python
(pypy36_1) oberstet@intel-nuci7:~/scm/crossbario/crossbarfx$ python -c "from hashlib import sha512 as _sha512"

is there a way to disable this pep517 stuff altogether?

[pradyunsg]

This seems to be #49+#45, and in the spirit of limited-time-triage, I'll go ahead and close this based on that judgement. Please holler if that looks wrong! :)