Including the venv

lib/python3.8/site-packages/pip/_vendor/pep517/__init__.py

@@ -0,0 +1,4 @@
+"""Wrappers to build Python packages using PEP 517 hooks
+"""
+
+__version__ = '0.5.0'

lib/python3.8/site-packages/pip/_vendor/pep517/_in_process.py

@@ -0,0 +1,207 @@
+"""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()

lib/python3.8/site-packages/pip/_vendor/pep517/build.py

@@ -0,0 +1,108 @@
+"""Build a project using PEP 517 hooks.
+"""
+import argparse
+import logging
+import os
+import contextlib
+from pip._vendor import pytoml
+import shutil
+import errno
+import tempfile
+
+from .envbuild import BuildEnvironment
+from .wrappers import Pep517HookCaller
+
+log = logging.getLogger(__name__)
+
+
+@contextlib.contextmanager
+def tempdir():
+    td = tempfile.mkdtemp()
+    try:
+        yield td
+    finally:
+        shutil.rmtree(td)
+
+
+def _do_build(hooks, env, dist, dest):
+    get_requires_name = 'get_requires_for_build_{dist}'.format(**locals())
+    get_requires = getattr(hooks, get_requires_name)
+    reqs = get_requires({})
+    log.info('Got build requires: %s', reqs)
+
+    env.pip_install(reqs)
+    log.info('Installed dynamic build dependencies')
+
+    with tempdir() as td:
+        log.info('Trying to build %s in %s', dist, td)
+        build_name = 'build_{dist}'.format(**locals())
+        build = getattr(hooks, build_name)
+        filename = build(td, {})
+        source = os.path.join(td, filename)
+        shutil.move(source, os.path.join(dest, os.path.basename(filename)))
+
+
+def mkdir_p(*args, **kwargs):
+    """Like `mkdir`, but does not raise an exception if the
+    directory already exists.
+    """
+    try:
+        return os.mkdir(*args, **kwargs)
+    except OSError as exc:
+        if exc.errno != errno.EEXIST:
+            raise
+
+
+def build(source_dir, dist, dest=None):
+    pyproject = os.path.join(source_dir, 'pyproject.toml')
+    dest = os.path.join(source_dir, dest or 'dist')
+    mkdir_p(dest)
+
+    with open(pyproject) as f:
+        pyproject_data = pytoml.load(f)
+    # Ensure the mandatory data can be loaded
+    buildsys = pyproject_data['build-system']
+    requires = buildsys['requires']
+    backend = buildsys['build-backend']
+
+    hooks = Pep517HookCaller(source_dir, backend)
+
+    with BuildEnvironment() as env:
+        env.pip_install(requires)
+        _do_build(hooks, env, dist, dest)
+
+
+parser = argparse.ArgumentParser()
+parser.add_argument(
+    'source_dir',
+    help="A directory containing pyproject.toml",
+)
+parser.add_argument(
+    '--binary', '-b',
+    action='store_true',
+    default=False,
+)
+parser.add_argument(
+    '--source', '-s',
+    action='store_true',
+    default=False,
+)
+parser.add_argument(
+    '--out-dir', '-o',
+    help="Destination in which to save the builds relative to source dir",
+)
+
+
+def main(args):
+    # determine which dists to build
+    dists = list(filter(None, (
+        'sdist' if args.source or not args.binary else None,
+        'wheel' if args.binary or not args.source else None,
+    )))
+
+    for dist in dists:
+        build(args.source_dir, dist, args.out_dir)
+
+
+if __name__ == '__main__':
+    main(parser.parse_args())

lib/python3.8/site-packages/pip/_vendor/pep517/check.py

@@ -0,0 +1,202 @@
+"""Check a project and backend by attempting to build using PEP 517 hooks.
+"""
+import argparse
+import logging
+import os
+from os.path import isfile, join as pjoin
+from pip._vendor.pytoml import TomlError, load as toml_load
+import shutil
+from subprocess import CalledProcessError
+import sys
+import tarfile
+from tempfile import mkdtemp
+import zipfile
+
+from .colorlog import enable_colourful_output
+from .envbuild import BuildEnvironment
+from .wrappers import Pep517HookCaller
+
+log = logging.getLogger(__name__)
+
+
+def check_build_sdist(hooks, build_sys_requires):
+    with BuildEnvironment() as env:
+        try:
+            env.pip_install(build_sys_requires)
+            log.info('Installed static build dependencies')
+        except CalledProcessError:
+            log.error('Failed to install static build dependencies')
+            return False
+
+        try:
+            reqs = hooks.get_requires_for_build_sdist({})
+            log.info('Got build requires: %s', reqs)
+        except Exception:
+            log.error('Failure in get_requires_for_build_sdist', exc_info=True)
+            return False
+
+        try:
+            env.pip_install(reqs)
+            log.info('Installed dynamic build dependencies')
+        except CalledProcessError:
+            log.error('Failed to install dynamic build dependencies')
+            return False
+
+        td = mkdtemp()
+        log.info('Trying to build sdist in %s', td)
+        try:
+            try:
+                filename = hooks.build_sdist(td, {})
+                log.info('build_sdist returned %r', filename)
+            except Exception:
+                log.info('Failure in build_sdist', exc_info=True)
+                return False
+
+            if not filename.endswith('.tar.gz'):
+                log.error(
+                    "Filename %s doesn't have .tar.gz extension", filename)
+                return False
+
+            path = pjoin(td, filename)
+            if isfile(path):
+                log.info("Output file %s exists", path)
+            else:
+                log.error("Output file %s does not exist", path)
+                return False
+
+            if tarfile.is_tarfile(path):
+                log.info("Output file is a tar file")
+            else:
+                log.error("Output file is not a tar file")
+                return False
+
+        finally:
+            shutil.rmtree(td)
+
+        return True
+
+
+def check_build_wheel(hooks, build_sys_requires):
+    with BuildEnvironment() as env:
+        try:
+            env.pip_install(build_sys_requires)
+            log.info('Installed static build dependencies')
+        except CalledProcessError:
+            log.error('Failed to install static build dependencies')
+            return False
+
+        try:
+            reqs = hooks.get_requires_for_build_wheel({})
+            log.info('Got build requires: %s', reqs)
+        except Exception:
+            log.error('Failure in get_requires_for_build_sdist', exc_info=True)
+            return False
+
+        try:
+            env.pip_install(reqs)
+            log.info('Installed dynamic build dependencies')
+        except CalledProcessError:
+            log.error('Failed to install dynamic build dependencies')
+            return False
+
+        td = mkdtemp()
+        log.info('Trying to build wheel in %s', td)
+        try:
+            try:
+                filename = hooks.build_wheel(td, {})
+                log.info('build_wheel returned %r', filename)
+            except Exception:
+                log.info('Failure in build_wheel', exc_info=True)
+                return False
+
+            if not filename.endswith('.whl'):
+                log.error("Filename %s doesn't have .whl extension", filename)
+                return False
+
+            path = pjoin(td, filename)
+            if isfile(path):
+                log.info("Output file %s exists", path)
+            else:
+                log.error("Output file %s does not exist", path)
+                return False
+
+            if zipfile.is_zipfile(path):
+                log.info("Output file is a zip file")
+            else:
+                log.error("Output file is not a zip file")
+                return False
+
+        finally:
+            shutil.rmtree(td)
+
+        return True
+
+
+def check(source_dir):
+    pyproject = pjoin(source_dir, 'pyproject.toml')
+    if isfile(pyproject):
+        log.info('Found pyproject.toml')
+    else:
+        log.error('Missing pyproject.toml')
+        return False
+
+    try:
+        with open(pyproject) as f:
+            pyproject_data = toml_load(f)
+        # Ensure the mandatory data can be loaded
+        buildsys = pyproject_data['build-system']
+        requires = buildsys['requires']
+        backend = buildsys['build-backend']
+        log.info('Loaded pyproject.toml')
+    except (TomlError, KeyError):
+        log.error("Invalid pyproject.toml", exc_info=True)
+        return False
+
+    hooks = Pep517HookCaller(source_dir, backend)
+
+    sdist_ok = check_build_sdist(hooks, requires)
+    wheel_ok = check_build_wheel(hooks, requires)
+
+    if not sdist_ok:
+        log.warning('Sdist checks failed; scroll up to see')
+    if not wheel_ok:
+        log.warning('Wheel checks failed')
+
+    return sdist_ok
+
+
+def main(argv=None):
+    ap = argparse.ArgumentParser()
+    ap.add_argument(
+        'source_dir',
+        help="A directory containing pyproject.toml")
+    args = ap.parse_args(argv)
+
+    enable_colourful_output()
+
+    ok = check(args.source_dir)
+
+    if ok:
+        print(ansi('Checks passed', 'green'))
+    else:
+        print(ansi('Checks failed', 'red'))
+        sys.exit(1)
+
+
+ansi_codes = {
+    'reset': '\x1b[0m',
+    'bold': '\x1b[1m',
+    'red': '\x1b[31m',
+    'green': '\x1b[32m',
+}
+
+
+def ansi(s, attr):
+    if os.name != 'nt' and sys.stdout.isatty():
+        return ansi_codes[attr] + str(s) + ansi_codes['reset']
+    else:
+        return str(s)
+
+
+if __name__ == '__main__':
+    main()

lib/python3.8/site-packages/pip/_vendor/pep517/colorlog.py

@@ -0,0 +1,115 @@
+"""Nicer log formatting with colours.
+
+Code copied from Tornado, Apache licensed.
+"""
+# Copyright 2012 Facebook
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License. You may obtain
+# a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations
+# under the License.
+
+import logging
+import sys
+
+try:
+    import curses
+except ImportError:
+    curses = None
+
+
+def _stderr_supports_color():
+    color = False
+    if curses and hasattr(sys.stderr, 'isatty') and sys.stderr.isatty():
+        try:
+            curses.setupterm()
+            if curses.tigetnum("colors") > 0:
+                color = True
+        except Exception:
+            pass
+    return color
+
+
+class LogFormatter(logging.Formatter):
+    """Log formatter with colour support
+    """
+    DEFAULT_COLORS = {
+        logging.INFO: 2,  # Green
+        logging.WARNING: 3,  # Yellow
+        logging.ERROR: 1,  # Red
+        logging.CRITICAL: 1,
+    }
+
+    def __init__(self, color=True, datefmt=None):
+        r"""
+        :arg bool color: Enables color support.
+        :arg string fmt: Log message format.
+        It will be applied to the attributes dict of log records. The
+        text between ``%(color)s`` and ``%(end_color)s`` will be colored
+        depending on the level if color support is on.
+        :arg dict colors: color mappings from logging level to terminal color
+        code
+        :arg string datefmt: Datetime format.
+        Used for formatting ``(asctime)`` placeholder in ``prefix_fmt``.
+        .. versionchanged:: 3.2
+        Added ``fmt`` and ``datefmt`` arguments.
+        """
+        logging.Formatter.__init__(self, datefmt=datefmt)
+        self._colors = {}
+        if color and _stderr_supports_color():
+            # The curses module has some str/bytes confusion in
+            # python3. Until version 3.2.3, most methods return
+            # bytes, but only accept strings. In addition, we want to
+            # output these strings with the logging module, which
+            # works with unicode strings. The explicit calls to
+            # unicode() below are harmless in python2 but will do the
+            # right conversion in python 3.
+            fg_color = (curses.tigetstr("setaf") or
+                        curses.tigetstr("setf") or "")
+            if (3, 0) < sys.version_info < (3, 2, 3):
+                fg_color = str(fg_color, "ascii")
+
+            for levelno, code in self.DEFAULT_COLORS.items():
+                self._colors[levelno] = str(
+                    curses.tparm(fg_color, code), "ascii")
+            self._normal = str(curses.tigetstr("sgr0"), "ascii")
+
+            scr = curses.initscr()
+            self.termwidth = scr.getmaxyx()[1]
+            curses.endwin()
+        else:
+            self._normal = ''
+            # Default width is usually 80, but too wide is
+            # worse than too narrow
+            self.termwidth = 70
+
+    def formatMessage(self, record):
+        mlen = len(record.message)
+        right_text = '{initial}-{name}'.format(initial=record.levelname[0],
+                                               name=record.name)
+        if mlen + len(right_text) < self.termwidth:
+            space = ' ' * (self.termwidth - (mlen + len(right_text)))
+        else:
+            space = '  '
+
+        if record.levelno in self._colors:
+            start_color = self._colors[record.levelno]
+            end_color = self._normal
+        else:
+            start_color = end_color = ''
+
+        return record.message + space + start_color + right_text + end_color
+
+
+def enable_colourful_output(level=logging.INFO):
+    handler = logging.StreamHandler()
+    handler.setFormatter(LogFormatter())
+    logging.root.addHandler(handler)
+    logging.root.setLevel(level)

lib/python3.8/site-packages/pip/_vendor/pep517/compat.py

@@ -0,0 +1,23 @@
+"""Handle reading and writing JSON in UTF-8, on Python 3 and 2."""
+import json
+import sys
+
+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)

lib/python3.8/site-packages/pip/_vendor/pep517/envbuild.py

@@ -0,0 +1,158 @@
+"""Build wheels/sdists by installing build deps to a temporary environment.
+"""
+
+import os
+import logging
+from pip._vendor import pytoml
+import shutil
+from subprocess import check_call
+import sys
+from sysconfig import get_paths
+from tempfile import mkdtemp
+
+from .wrappers import Pep517HookCaller
+
+log = logging.getLogger(__name__)
+
+
+def _load_pyproject(source_dir):
+    with open(os.path.join(source_dir, 'pyproject.toml')) as f:
+        pyproject_data = pytoml.load(f)
+    buildsys = pyproject_data['build-system']
+    return buildsys['requires'], buildsys['build-backend']
+
+
+class BuildEnvironment(object):
+    """Context manager to install build deps in a simple temporary environment
+
+    Based on code I wrote for pip, which is MIT licensed.
+    """
+    # Copyright (c) 2008-2016 The pip developers (see AUTHORS.txt file)
+    #
+    # Permission is hereby granted, free of charge, to any person obtaining
+    # a copy of this software and associated documentation files (the
+    # "Software"), to deal in the Software without restriction, including
+    # without limitation the rights to use, copy, modify, merge, publish,
+    # distribute, sublicense, and/or sell copies of the Software, and to
+    # permit persons to whom the Software is furnished to do so, subject to
+    # the following conditions:
+    #
+    # The above copyright notice and this permission notice shall be
+    # included in all copies or substantial portions of the Software.
+    #
+    # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+    # EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+    # MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+    # NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+    # LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+    # OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+    # WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+    path = None
+
+    def __init__(self, cleanup=True):
+        self._cleanup = cleanup
+
+    def __enter__(self):
+        self.path = mkdtemp(prefix='pep517-build-env-')
+        log.info('Temporary build environment: %s', self.path)
+
+        self.save_path = os.environ.get('PATH', None)
+        self.save_pythonpath = os.environ.get('PYTHONPATH', None)
+
+        install_scheme = 'nt' if (os.name == 'nt') else 'posix_prefix'
+        install_dirs = get_paths(install_scheme, vars={
+            'base': self.path,
+            'platbase': self.path,
+        })
+
+        scripts = install_dirs['scripts']
+        if self.save_path:
+            os.environ['PATH'] = scripts + os.pathsep + self.save_path
+        else:
+            os.environ['PATH'] = scripts + os.pathsep + os.defpath
+
+        if install_dirs['purelib'] == install_dirs['platlib']:
+            lib_dirs = install_dirs['purelib']
+        else:
+            lib_dirs = install_dirs['purelib'] + os.pathsep + \
+                install_dirs['platlib']
+        if self.save_pythonpath:
+            os.environ['PYTHONPATH'] = lib_dirs + os.pathsep + \
+                self.save_pythonpath
+        else:
+            os.environ['PYTHONPATH'] = lib_dirs
+
+        return self
+
+    def pip_install(self, reqs):
+        """Install dependencies into this env by calling pip in a subprocess"""
+        if not reqs:
+            return
+        log.info('Calling pip to install %s', reqs)
+        check_call([
+            sys.executable, '-m', 'pip', 'install', '--ignore-installed',
+            '--prefix', self.path] + list(reqs))
+
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        needs_cleanup = (
+            self._cleanup and
+            self.path is not None and
+            os.path.isdir(self.path)
+        )
+        if needs_cleanup:
+            shutil.rmtree(self.path)
+
+        if self.save_path is None:
+            os.environ.pop('PATH', None)
+        else:
+            os.environ['PATH'] = self.save_path
+
+        if self.save_pythonpath is None:
+            os.environ.pop('PYTHONPATH', None)
+        else:
+            os.environ['PYTHONPATH'] = self.save_pythonpath
+
+
+def build_wheel(source_dir, wheel_dir, config_settings=None):
+    """Build a wheel from a source directory using PEP 517 hooks.
+
+    :param str source_dir: Source directory containing pyproject.toml
+    :param str wheel_dir: Target directory to create wheel in
+    :param dict config_settings: Options to pass to build backend
+
+    This is a blocking function which will run pip in a subprocess to install
+    build requirements.
+    """
+    if config_settings is None:
+        config_settings = {}
+    requires, backend = _load_pyproject(source_dir)
+    hooks = Pep517HookCaller(source_dir, backend)
+
+    with BuildEnvironment() as env:
+        env.pip_install(requires)
+        reqs = hooks.get_requires_for_build_wheel(config_settings)
+        env.pip_install(reqs)
+        return hooks.build_wheel(wheel_dir, config_settings)
+
+
+def build_sdist(source_dir, sdist_dir, config_settings=None):
+    """Build an sdist from a source directory using PEP 517 hooks.
+
+    :param str source_dir: Source directory containing pyproject.toml
+    :param str sdist_dir: Target directory to place sdist in
+    :param dict config_settings: Options to pass to build backend
+
+    This is a blocking function which will run pip in a subprocess to install
+    build requirements.
+    """
+    if config_settings is None:
+        config_settings = {}
+    requires, backend = _load_pyproject(source_dir)
+    hooks = Pep517HookCaller(source_dir, backend)
+
+    with BuildEnvironment() as env:
+        env.pip_install(requires)
+        reqs = hooks.get_requires_for_build_sdist(config_settings)
+        env.pip_install(reqs)
+        return hooks.build_sdist(sdist_dir, config_settings)

lib/python3.8/site-packages/pip/_vendor/pep517/wrappers.py

@@ -0,0 +1,163 @@
+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']