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from contextlib import contextmanager
import os
from os.path import dirname, abspath, join as pjoin
import shutil
from subprocess import check_call
import sys
from tempfile import mkdtemp
from . import compat
_in_proc_script = pjoin(dirname(abspath(__file__)), '_in_process.py')
@contextmanager
def tempdir():
td = mkdtemp()
try:
yield td
finally:
shutil.rmtree(td)
class BackendUnavailable(Exception):
"""Will be raised if the backend cannot be imported in the hook process."""
class UnsupportedOperation(Exception):
"""May be raised by build_sdist if the backend indicates that it can't."""
def default_subprocess_runner(cmd, cwd=None, extra_environ=None):
"""The default method of calling the wrapper subprocess."""
env = os.environ.copy()
if extra_environ:
env.update(extra_environ)
check_call(cmd, cwd=cwd, env=env)
class Pep517HookCaller(object):
"""A wrapper around a source directory to be built with a PEP 517 backend.
source_dir : The path to the source directory, containing pyproject.toml.
backend : The build backend spec, as per PEP 517, from pyproject.toml.
"""
def __init__(self, source_dir, build_backend):
self.source_dir = abspath(source_dir)
self.build_backend = build_backend
self._subprocess_runner = default_subprocess_runner
# TODO: Is this over-engineered? Maybe frontends only need to
# set this when creating the wrapper, not on every call.
@contextmanager
def subprocess_runner(self, runner):
prev = self._subprocess_runner
self._subprocess_runner = runner
yield
self._subprocess_runner = prev
def get_requires_for_build_wheel(self, config_settings=None):
"""Identify packages required for building a wheel
Returns a list of dependency specifications, e.g.:
["wheel >= 0.25", "setuptools"]
This does not include requirements specified in pyproject.toml.
It returns the result of calling the equivalently named hook in a
subprocess.
"""
return self._call_hook('get_requires_for_build_wheel', {
'config_settings': config_settings
})
def prepare_metadata_for_build_wheel(
self, metadata_directory, config_settings=None):
"""Prepare a *.dist-info folder with metadata for this project.
Returns the name of the newly created folder.
If the build backend defines a hook with this name, it will be called
in a subprocess. If not, the backend will be asked to build a wheel,
and the dist-info extracted from that.
"""
return self._call_hook('prepare_metadata_for_build_wheel', {
'metadata_directory': abspath(metadata_directory),
'config_settings': config_settings,
})
def build_wheel(
self, wheel_directory, config_settings=None,
metadata_directory=None):
"""Build a wheel from this project.
Returns the name of the newly created file.
In general, this will call the 'build_wheel' hook in the backend.
However, if that was previously called by
'prepare_metadata_for_build_wheel', and the same metadata_directory is
used, the previously built wheel will be copied to wheel_directory.
"""
if metadata_directory is not None:
metadata_directory = abspath(metadata_directory)
return self._call_hook('build_wheel', {
'wheel_directory': abspath(wheel_directory),
'config_settings': config_settings,
'metadata_directory': metadata_directory,
})
def get_requires_for_build_sdist(self, config_settings=None):
"""Identify packages required for building a wheel
Returns a list of dependency specifications, e.g.:
["setuptools >= 26"]
This does not include requirements specified in pyproject.toml.
It returns the result of calling the equivalently named hook in a
subprocess.
"""
return self._call_hook('get_requires_for_build_sdist', {
'config_settings': config_settings
})
def build_sdist(self, sdist_directory, config_settings=None):
"""Build an sdist from this project.
Returns the name of the newly created file.
This calls the 'build_sdist' backend hook in a subprocess.
"""
return self._call_hook('build_sdist', {
'sdist_directory': abspath(sdist_directory),
'config_settings': config_settings,
})
def _call_hook(self, hook_name, kwargs):
# On Python 2, pytoml returns Unicode values (which is correct) but the
# environment passed to check_call needs to contain string values. We
# convert here by encoding using ASCII (the backend can only contain
# letters, digits and _, . and : characters, and will be used as a
# Python identifier, so non-ASCII content is wrong on Python 2 in
# any case).
if sys.version_info[0] == 2:
build_backend = self.build_backend.encode('ASCII')
else:
build_backend = self.build_backend
with tempdir() as td:
compat.write_json({'kwargs': kwargs}, pjoin(td, 'input.json'),
indent=2)
# Run the hook in a subprocess
self._subprocess_runner(
[sys.executable, _in_proc_script, hook_name, td],
cwd=self.source_dir,
extra_environ={'PEP517_BUILD_BACKEND': build_backend}
)
data = compat.read_json(pjoin(td, 'output.json'))
if data.get('unsupported'):
raise UnsupportedOperation
if data.get('no_backend'):
raise BackendUnavailable
return data['return_val']
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