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"""This is invoked in a subprocess to call the build backend hooks.
It expects:
- Command line args: hook_name, control_dir
- Environment variable: PEP517_BUILD_BACKEND=entry.point:spec
- control_dir/input.json:
- {"kwargs": {...}}
Results:
- control_dir/output.json
- {"return_val": ...}
"""
from glob import glob
from importlib import import_module
import os
from os.path import join as pjoin
import re
import shutil
import sys
# This is run as a script, not a module, so it can't do a relative import
import compat
class BackendUnavailable(Exception):
"""Raised if we cannot import the backend"""
def _build_backend():
"""Find and load the build backend"""
ep = os.environ['PEP517_BUILD_BACKEND']
mod_path, _, obj_path = ep.partition(':')
try:
obj = import_module(mod_path)
except ImportError:
raise BackendUnavailable
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):
"""Invoke optional prepare_metadata_for_build_wheel
Implements a fallback by building a wheel if the hook isn't defined.
"""
backend = _build_backend()
try:
hook = backend.prepare_metadata_for_build_wheel
except AttributeError:
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 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
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 = compat.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:
json_out['no_backend'] = True
except GotUnsupportedOperation:
json_out['unsupported'] = True
compat.write_json(json_out, pjoin(control_dir, 'output.json'), indent=2)
if __name__ == '__main__':
main()
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