"""This is invoked in a subprocess to call the build backend hooks.
It expects:
- Command line args: hook_name, control_dir
- Environment variables:
PEP517_BUILD_BACKEND=entry.point:spec
PEP517_BACKEND_PATH=paths (separated with os.pathsep)
- control_dir/input.json:
- {"kwargs": {...}}
Results:
- control_dir/output.json
- {"return_val": ...}
"""
from glob import glob
from importlib import import_module
import json
import os
import os.path
from os.path import join as pjoin
import re
import shutil
import sys
import traceback
# This file is run as a script, and `import compat` is not zip-safe, so we
# include write_json() and read_json() from compat.py.
#
# Handle reading and writing JSON in UTF-8, on Python 3 and 2.
if sys.version_info[0] >= 3:
# Python 3
def write_json(obj, path, **kwargs):
with open(path, 'w', encoding='utf-8') as f:
json.dump(obj, f, **kwargs)
def read_json(path):
with open(path, 'r', encoding='utf-8') as f:
return json.load(f)
else:
# Python 2
def write_json(obj, path, **kwargs):
with open(path, 'wb') as f:
json.dump(obj, f, encoding='utf-8', **kwargs)
def read_json(path):
with open(path, 'rb') as f:
return json.load(f)
class BackendUnavailable(Exception):
"""Raised if we cannot import the backend"""
def __init__(self, traceback):
self.traceback = traceback
class BackendInvalid(Exception):
"""Raised if the backend is invalid"""
def __init__(self, message):
self.message = message
class HookMissing(Exception):
"""Raised if a hook is missing and we are not executing the fallback"""
def contained_in(filename, directory):
"""Test if a file is located within the given directory."""
filename = os.path.normcase(os.path.abspath(filename))
directory = os.path.normcase(os.path.abspath(directory))
return os.path.commonprefix([filename, directory]) == directory
def _build_backend():
"""Find and load the build backend"""
# Add in-tree backend directories to the front of sys.path.
backend_path = os.environ.get('PEP517_BACKEND_PATH')
if backend_path:
extra_pathitems = backend_path.split(os.pathsep)
sys.path[:0] = extra_pathitems
ep = os.environ['PEP517_BUILD_BACKEND']
mod_path, _, obj_path = ep.partition(':')
try:
obj = import_module(mod_path)
except ImportError:
raise BackendUnavailable(traceback.format_exc())
if backend_path:
if not any(
contained_in(obj.__file__, path)
for path in extra_pathitems
):
raise BackendInvalid("Backend was not loaded from backend-path")
if obj_path:
for path_part in obj_path.split('.'):
obj = getattr(obj, path_part)
return obj
def get_requires_for_build_wheel(config_settings):
"""Invoke the optional get_requires_for_build_wheel hook
Returns [] if the hook is not defined.
"""
backend = _build_backend()
try:
hook = backend.get_requires_for_build_wheel
except AttributeError:
return []
else:
return hook(config_settings)
def prepare_metadata_for_build_wheel(
metadata_directory, config_settings, _allow_fallback):
"""Invoke optional prepare_metadata_for_build_wheel
Implements a fallback by building a wheel if the hook isn't defined,
unless _allow_fallback is False in which case HookMissing is raised.
"""
backend = _build_backend()
try:
hook = backend.prepare_metadata_for_build_wheel
except AttributeError:
if not _allow_fallback:
raise HookMissing()
return _get_wheel_metadata_from_wheel(backend, metadata_directory,
config_settings)
else:
return hook(metadata_directory, config_settings)
WHEEL_BUILT_MARKER = 'PEP517_ALREADY_BUILT_WHEEL'
def _dist_info_files(whl_zip):
"""Identify the .dist-info folder inside a wheel ZipFile."""
res = []
for path in whl_zip.namelist():
m = re.match(r'[^/\\]+-[^/\\]+\.dist-info/', path)
if m:
res.append(path)
if res:
return res
raise Exception("No .dist-info folder found in wheel")
def _get_wheel_metadata_from_wheel(
backend, metadata_directory, config_settings):
"""Build a wheel and extract the metadata from it.
Fallback for when the build backend does not
define the 'get_wheel_metadata' hook.
"""
from zipfile import ZipFile
whl_basename = backend.build_wheel(metadata_directory, config_settings)
with open(os.path.join(metadata_directory, WHEEL_BUILT_MARKER), 'wb'):
pass # Touch marker file
whl_file = os.path.join(metadata_directory, whl_basename)
with ZipFile(whl_file) as zipf:
dist_info = _dist_info_files(zipf)
zipf.extractall(path=metadata_directory, members=dist_info)
return dist_info[0].split('/')[0]
def _find_already_built_wheel(metadata_directory):
"""Check for a wheel already built during the get_wheel_metadata hook.
"""
if not metadata_directory:
return None
metadata_parent = os.path.dirname(metadata_directory)
if not os.path.isfile(pjoin(metadata_parent, WHEEL_BUILT_MARKER)):
return None
whl_files = glob(os.path.join(metadata_parent, '*.whl'))
if not whl_files:
print('Found wheel built marker, but no .whl files')
return None
if len(whl_files) > 1:
print('Found multiple .whl files; unspecified behaviour. '
'Will call build_wheel.')
return None
# Exactly one .whl file
return whl_files[0]
def build_wheel(wheel_directory, config_settings, metadata_directory=None):
"""Invoke the mandatory build_wheel hook.
If a wheel was already built in the
prepare_metadata_for_build_wheel fallback, this
will copy it rather than rebuilding the wheel.
"""
prebuilt_whl = _find_already_built_wheel(metadata_directory)
if prebuilt_whl:
shutil.copy2(prebuilt_whl, wheel_directory)
return os.path.basename(prebuilt_whl)
return _build_backend().build_wheel(wheel_directory, config_settings,
metadata_directory)
def get_requires_for_build_sdist(config_settings):
"""Invoke the optional get_requires_for_build_wheel hook
Returns [] if the hook is not defined.
"""
backend = _build_backend()
try:
hook = backend.get_requires_for_build_sdist
except AttributeError:
return []
else:
return hook(config_settings)
class _DummyException(Exception):
"""Nothing should ever raise this exception"""
class GotUnsupportedOperation(Exception):
"""For internal use when backend raises UnsupportedOperation"""
def __init__(self, traceback):
self.traceback = traceback
def build_sdist(sdist_directory, config_settings):
"""Invoke the mandatory build_sdist hook."""
backend = _build_backend()
try:
return backend.build_sdist(sdist_directory, config_settings)
except getattr(backend, 'UnsupportedOperation', _DummyException):
raise GotUnsupportedOperation(traceback.format_exc())
HOOK_NAMES = {
'get_requires_for_build_wheel',
'prepare_metadata_for_build_wheel',
'build_wheel',
'get_requires_for_build_sdist',
'build_sdist',
}
def main():
if len(sys.argv) < 3:
sys.exit("Needs args: hook_name, control_dir")
hook_name = sys.argv[1]
control_dir = sys.argv[2]
if hook_name not in HOOK_NAMES:
sys.exit("Unknown hook: %s" % hook_name)
hook = globals()[hook_name]
hook_input = read_json(pjoin(control_dir, 'input.json'))
json_out = {'unsupported': False, 'return_val': None}
try:
json_out['return_val'] = hook(**hook_input['kwargs'])
except BackendUnavailable as e:
json_out['no_backend'] = True
json_out['traceback'] = e.traceback
except BackendInvalid as e:
json_out['backend_invalid'] = True
json_out['backend_error'] = e.message
except GotUnsupportedOperation as e:
json_out['unsupported'] = True
json_out['traceback'] = e.traceback
except HookMissing:
json_out['hook_missing'] = True
write_json(json_out, pjoin(control_dir, 'output.json'), indent=2)
if __name__ == '__main__':
main()