--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/planemo/lib/python3.7/site-packages/pip/_internal/wheel.py	Fri Jul 31 00:32:28 2020 -0400
@@ -0,0 +1,1125 @@
+"""
+Support for installing and building the "wheel" binary package format.
+"""
+from __future__ import absolute_import
+
+import collections
+import compileall
+import csv
+import hashlib
+import logging
+import os.path
+import re
+import shutil
+import stat
+import sys
+import warnings
+from base64 import urlsafe_b64encode
+from email.parser import Parser
+
+from pip._vendor import pkg_resources
+from pip._vendor.distlib.scripts import ScriptMaker
+from pip._vendor.packaging.utils import canonicalize_name
+from pip._vendor.six import StringIO
+
+from pip._internal import pep425tags
+from pip._internal.download import unpack_url
+from pip._internal.exceptions import (
+    InstallationError, InvalidWheelFilename, UnsupportedWheel,
+)
+from pip._internal.locations import distutils_scheme
+from pip._internal.models.link import Link
+from pip._internal.utils.logging import indent_log
+from pip._internal.utils.marker_files import PIP_DELETE_MARKER_FILENAME
+from pip._internal.utils.misc import (
+    LOG_DIVIDER, call_subprocess, captured_stdout, ensure_dir,
+    format_command_args, path_to_url, read_chunks,
+)
+from pip._internal.utils.setuptools_build import make_setuptools_shim_args
+from pip._internal.utils.temp_dir import TempDirectory
+from pip._internal.utils.typing import MYPY_CHECK_RUNNING
+from pip._internal.utils.ui import open_spinner
+
+if MYPY_CHECK_RUNNING:
+    from typing import (
+        Dict, List, Optional, Sequence, Mapping, Tuple, IO, Text, Any, Iterable
+    )
+    from pip._vendor.packaging.requirements import Requirement
+    from pip._internal.req.req_install import InstallRequirement
+    from pip._internal.download import PipSession
+    from pip._internal.index import FormatControl, PackageFinder
+    from pip._internal.operations.prepare import (
+        RequirementPreparer
+    )
+    from pip._internal.cache import WheelCache
+    from pip._internal.pep425tags import Pep425Tag
+
+    InstalledCSVRow = Tuple[str, ...]
+
+
+VERSION_COMPATIBLE = (1, 0)
+
+
+logger = logging.getLogger(__name__)
+
+
+def normpath(src, p):
+    return os.path.relpath(src, p).replace(os.path.sep, '/')
+
+
+def hash_file(path, blocksize=1 << 20):
+    # type: (str, int) -> Tuple[Any, int]
+    """Return (hash, length) for path using hashlib.sha256()"""
+    h = hashlib.sha256()
+    length = 0
+    with open(path, 'rb') as f:
+        for block in read_chunks(f, size=blocksize):
+            length += len(block)
+            h.update(block)
+    return (h, length)  # type: ignore
+
+
+def rehash(path, blocksize=1 << 20):
+    # type: (str, int) -> Tuple[str, str]
+    """Return (encoded_digest, length) for path using hashlib.sha256()"""
+    h, length = hash_file(path, blocksize)
+    digest = 'sha256=' + urlsafe_b64encode(
+        h.digest()
+    ).decode('latin1').rstrip('=')
+    # unicode/str python2 issues
+    return (digest, str(length))  # type: ignore
+
+
+def open_for_csv(name, mode):
+    # type: (str, Text) -> IO
+    if sys.version_info[0] < 3:
+        nl = {}  # type: Dict[str, Any]
+        bin = 'b'
+    else:
+        nl = {'newline': ''}  # type: Dict[str, Any]
+        bin = ''
+    return open(name, mode + bin, **nl)
+
+
+def replace_python_tag(wheelname, new_tag):
+    # type: (str, str) -> str
+    """Replace the Python tag in a wheel file name with a new value.
+    """
+    parts = wheelname.split('-')
+    parts[-3] = new_tag
+    return '-'.join(parts)
+
+
+def fix_script(path):
+    # type: (str) -> Optional[bool]
+    """Replace #!python with #!/path/to/python
+    Return True if file was changed."""
+    # XXX RECORD hashes will need to be updated
+    if os.path.isfile(path):
+        with open(path, 'rb') as script:
+            firstline = script.readline()
+            if not firstline.startswith(b'#!python'):
+                return False
+            exename = sys.executable.encode(sys.getfilesystemencoding())
+            firstline = b'#!' + exename + os.linesep.encode("ascii")
+            rest = script.read()
+        with open(path, 'wb') as script:
+            script.write(firstline)
+            script.write(rest)
+        return True
+    return None
+
+
+dist_info_re = re.compile(r"""^(?P<namever>(?P<name>.+?)(-(?P<ver>.+?))?)
+                                \.dist-info$""", re.VERBOSE)
+
+
+def root_is_purelib(name, wheeldir):
+    # type: (str, str) -> bool
+    """
+    Return True if the extracted wheel in wheeldir should go into purelib.
+    """
+    name_folded = name.replace("-", "_")
+    for item in os.listdir(wheeldir):
+        match = dist_info_re.match(item)
+        if match and match.group('name') == name_folded:
+            with open(os.path.join(wheeldir, item, 'WHEEL')) as wheel:
+                for line in wheel:
+                    line = line.lower().rstrip()
+                    if line == "root-is-purelib: true":
+                        return True
+    return False
+
+
+def get_entrypoints(filename):
+    # type: (str) -> Tuple[Dict[str, str], Dict[str, str]]
+    if not os.path.exists(filename):
+        return {}, {}
+
+    # This is done because you can pass a string to entry_points wrappers which
+    # means that they may or may not be valid INI files. The attempt here is to
+    # strip leading and trailing whitespace in order to make them valid INI
+    # files.
+    with open(filename) as fp:
+        data = StringIO()
+        for line in fp:
+            data.write(line.strip())
+            data.write("\n")
+        data.seek(0)
+
+    # get the entry points and then the script names
+    entry_points = pkg_resources.EntryPoint.parse_map(data)
+    console = entry_points.get('console_scripts', {})
+    gui = entry_points.get('gui_scripts', {})
+
+    def _split_ep(s):
+        """get the string representation of EntryPoint, remove space and split
+        on '='"""
+        return str(s).replace(" ", "").split("=")
+
+    # convert the EntryPoint objects into strings with module:function
+    console = dict(_split_ep(v) for v in console.values())
+    gui = dict(_split_ep(v) for v in gui.values())
+    return console, gui
+
+
+def message_about_scripts_not_on_PATH(scripts):
+    # type: (Sequence[str]) -> Optional[str]
+    """Determine if any scripts are not on PATH and format a warning.
+
+    Returns a warning message if one or more scripts are not on PATH,
+    otherwise None.
+    """
+    if not scripts:
+        return None
+
+    # Group scripts by the path they were installed in
+    grouped_by_dir = collections.defaultdict(set)  # type: Dict[str, set]
+    for destfile in scripts:
+        parent_dir = os.path.dirname(destfile)
+        script_name = os.path.basename(destfile)
+        grouped_by_dir[parent_dir].add(script_name)
+
+    # We don't want to warn for directories that are on PATH.
+    not_warn_dirs = [
+        os.path.normcase(i).rstrip(os.sep) for i in
+        os.environ.get("PATH", "").split(os.pathsep)
+    ]
+    # If an executable sits with sys.executable, we don't warn for it.
+    #     This covers the case of venv invocations without activating the venv.
+    not_warn_dirs.append(os.path.normcase(os.path.dirname(sys.executable)))
+    warn_for = {
+        parent_dir: scripts for parent_dir, scripts in grouped_by_dir.items()
+        if os.path.normcase(parent_dir) not in not_warn_dirs
+    }
+    if not warn_for:
+        return None
+
+    # Format a message
+    msg_lines = []
+    for parent_dir, scripts in warn_for.items():
+        sorted_scripts = sorted(scripts)  # type: List[str]
+        if len(sorted_scripts) == 1:
+            start_text = "script {} is".format(sorted_scripts[0])
+        else:
+            start_text = "scripts {} are".format(
+                ", ".join(sorted_scripts[:-1]) + " and " + sorted_scripts[-1]
+            )
+
+        msg_lines.append(
+            "The {} installed in '{}' which is not on PATH."
+            .format(start_text, parent_dir)
+        )
+
+    last_line_fmt = (
+        "Consider adding {} to PATH or, if you prefer "
+        "to suppress this warning, use --no-warn-script-location."
+    )
+    if len(msg_lines) == 1:
+        msg_lines.append(last_line_fmt.format("this directory"))
+    else:
+        msg_lines.append(last_line_fmt.format("these directories"))
+
+    # Returns the formatted multiline message
+    return "\n".join(msg_lines)
+
+
+def sorted_outrows(outrows):
+    # type: (Iterable[InstalledCSVRow]) -> List[InstalledCSVRow]
+    """
+    Return the given rows of a RECORD file in sorted order.
+
+    Each row is a 3-tuple (path, hash, size) and corresponds to a record of
+    a RECORD file (see PEP 376 and PEP 427 for details).  For the rows
+    passed to this function, the size can be an integer as an int or string,
+    or the empty string.
+    """
+    # Normally, there should only be one row per path, in which case the
+    # second and third elements don't come into play when sorting.
+    # However, in cases in the wild where a path might happen to occur twice,
+    # we don't want the sort operation to trigger an error (but still want
+    # determinism).  Since the third element can be an int or string, we
+    # coerce each element to a string to avoid a TypeError in this case.
+    # For additional background, see--
+    # https://github.com/pypa/pip/issues/5868
+    return sorted(outrows, key=lambda row: tuple(str(x) for x in row))
+
+
+def get_csv_rows_for_installed(
+    old_csv_rows,  # type: Iterable[List[str]]
+    installed,  # type: Dict[str, str]
+    changed,  # type: set
+    generated,  # type: List[str]
+    lib_dir,  # type: str
+):
+    # type: (...) -> List[InstalledCSVRow]
+    """
+    :param installed: A map from archive RECORD path to installation RECORD
+        path.
+    """
+    installed_rows = []  # type: List[InstalledCSVRow]
+    for row in old_csv_rows:
+        if len(row) > 3:
+            logger.warning(
+                'RECORD line has more than three elements: {}'.format(row)
+            )
+        # Make a copy because we are mutating the row.
+        row = list(row)
+        old_path = row[0]
+        new_path = installed.pop(old_path, old_path)
+        row[0] = new_path
+        if new_path in changed:
+            digest, length = rehash(new_path)
+            row[1] = digest
+            row[2] = length
+        installed_rows.append(tuple(row))
+    for f in generated:
+        digest, length = rehash(f)
+        installed_rows.append((normpath(f, lib_dir), digest, str(length)))
+    for f in installed:
+        installed_rows.append((installed[f], '', ''))
+    return installed_rows
+
+
+def move_wheel_files(
+    name,  # type: str
+    req,  # type: Requirement
+    wheeldir,  # type: str
+    user=False,  # type: bool
+    home=None,  # type: Optional[str]
+    root=None,  # type: Optional[str]
+    pycompile=True,  # type: bool
+    scheme=None,  # type: Optional[Mapping[str, str]]
+    isolated=False,  # type: bool
+    prefix=None,  # type: Optional[str]
+    warn_script_location=True  # type: bool
+):
+    # type: (...) -> None
+    """Install a wheel"""
+    # TODO: Investigate and break this up.
+    # TODO: Look into moving this into a dedicated class for representing an
+    #       installation.
+
+    if not scheme:
+        scheme = distutils_scheme(
+            name, user=user, home=home, root=root, isolated=isolated,
+            prefix=prefix,
+        )
+
+    if root_is_purelib(name, wheeldir):
+        lib_dir = scheme['purelib']
+    else:
+        lib_dir = scheme['platlib']
+
+    info_dir = []  # type: List[str]
+    data_dirs = []
+    source = wheeldir.rstrip(os.path.sep) + os.path.sep
+
+    # Record details of the files moved
+    #   installed = files copied from the wheel to the destination
+    #   changed = files changed while installing (scripts #! line typically)
+    #   generated = files newly generated during the install (script wrappers)
+    installed = {}  # type: Dict[str, str]
+    changed = set()
+    generated = []  # type: List[str]
+
+    # Compile all of the pyc files that we're going to be installing
+    if pycompile:
+        with captured_stdout() as stdout:
+            with warnings.catch_warnings():
+                warnings.filterwarnings('ignore')
+                compileall.compile_dir(source, force=True, quiet=True)
+        logger.debug(stdout.getvalue())
+
+    def record_installed(srcfile, destfile, modified=False):
+        """Map archive RECORD paths to installation RECORD paths."""
+        oldpath = normpath(srcfile, wheeldir)
+        newpath = normpath(destfile, lib_dir)
+        installed[oldpath] = newpath
+        if modified:
+            changed.add(destfile)
+
+    def clobber(source, dest, is_base, fixer=None, filter=None):
+        ensure_dir(dest)  # common for the 'include' path
+
+        for dir, subdirs, files in os.walk(source):
+            basedir = dir[len(source):].lstrip(os.path.sep)
+            destdir = os.path.join(dest, basedir)
+            if is_base and basedir.split(os.path.sep, 1)[0].endswith('.data'):
+                continue
+            for s in subdirs:
+                destsubdir = os.path.join(dest, basedir, s)
+                if is_base and basedir == '' and destsubdir.endswith('.data'):
+                    data_dirs.append(s)
+                    continue
+                elif (is_base and
+                        s.endswith('.dist-info') and
+                        canonicalize_name(s).startswith(
+                            canonicalize_name(req.name))):
+                    assert not info_dir, ('Multiple .dist-info directories: ' +
+                                          destsubdir + ', ' +
+                                          ', '.join(info_dir))
+                    info_dir.append(destsubdir)
+            for f in files:
+                # Skip unwanted files
+                if filter and filter(f):
+                    continue
+                srcfile = os.path.join(dir, f)
+                destfile = os.path.join(dest, basedir, f)
+                # directory creation is lazy and after the file filtering above
+                # to ensure we don't install empty dirs; empty dirs can't be
+                # uninstalled.
+                ensure_dir(destdir)
+
+                # copyfile (called below) truncates the destination if it
+                # exists and then writes the new contents. This is fine in most
+                # cases, but can cause a segfault if pip has loaded a shared
+                # object (e.g. from pyopenssl through its vendored urllib3)
+                # Since the shared object is mmap'd an attempt to call a
+                # symbol in it will then cause a segfault. Unlinking the file
+                # allows writing of new contents while allowing the process to
+                # continue to use the old copy.
+                if os.path.exists(destfile):
+                    os.unlink(destfile)
+
+                # We use copyfile (not move, copy, or copy2) to be extra sure
+                # that we are not moving directories over (copyfile fails for
+                # directories) as well as to ensure that we are not copying
+                # over any metadata because we want more control over what
+                # metadata we actually copy over.
+                shutil.copyfile(srcfile, destfile)
+
+                # Copy over the metadata for the file, currently this only
+                # includes the atime and mtime.
+                st = os.stat(srcfile)
+                if hasattr(os, "utime"):
+                    os.utime(destfile, (st.st_atime, st.st_mtime))
+
+                # If our file is executable, then make our destination file
+                # executable.
+                if os.access(srcfile, os.X_OK):
+                    st = os.stat(srcfile)
+                    permissions = (
+                        st.st_mode | stat.S_IXUSR | stat.S_IXGRP | stat.S_IXOTH
+                    )
+                    os.chmod(destfile, permissions)
+
+                changed = False
+                if fixer:
+                    changed = fixer(destfile)
+                record_installed(srcfile, destfile, changed)
+
+    clobber(source, lib_dir, True)
+
+    assert info_dir, "%s .dist-info directory not found" % req
+
+    # Get the defined entry points
+    ep_file = os.path.join(info_dir[0], 'entry_points.txt')
+    console, gui = get_entrypoints(ep_file)
+
+    def is_entrypoint_wrapper(name):
+        # EP, EP.exe and EP-script.py are scripts generated for
+        # entry point EP by setuptools
+        if name.lower().endswith('.exe'):
+            matchname = name[:-4]
+        elif name.lower().endswith('-script.py'):
+            matchname = name[:-10]
+        elif name.lower().endswith(".pya"):
+            matchname = name[:-4]
+        else:
+            matchname = name
+        # Ignore setuptools-generated scripts
+        return (matchname in console or matchname in gui)
+
+    for datadir in data_dirs:
+        fixer = None
+        filter = None
+        for subdir in os.listdir(os.path.join(wheeldir, datadir)):
+            fixer = None
+            if subdir == 'scripts':
+                fixer = fix_script
+                filter = is_entrypoint_wrapper
+            source = os.path.join(wheeldir, datadir, subdir)
+            dest = scheme[subdir]
+            clobber(source, dest, False, fixer=fixer, filter=filter)
+
+    maker = ScriptMaker(None, scheme['scripts'])
+
+    # Ensure old scripts are overwritten.
+    # See https://github.com/pypa/pip/issues/1800
+    maker.clobber = True
+
+    # Ensure we don't generate any variants for scripts because this is almost
+    # never what somebody wants.
+    # See https://bitbucket.org/pypa/distlib/issue/35/
+    maker.variants = {''}
+
+    # This is required because otherwise distlib creates scripts that are not
+    # executable.
+    # See https://bitbucket.org/pypa/distlib/issue/32/
+    maker.set_mode = True
+
+    # Simplify the script and fix the fact that the default script swallows
+    # every single stack trace.
+    # See https://bitbucket.org/pypa/distlib/issue/34/
+    # See https://bitbucket.org/pypa/distlib/issue/33/
+    def _get_script_text(entry):
+        if entry.suffix is None:
+            raise InstallationError(
+                "Invalid script entry point: %s for req: %s - A callable "
+                "suffix is required. Cf https://packaging.python.org/en/"
+                "latest/distributing.html#console-scripts for more "
+                "information." % (entry, req)
+            )
+        return maker.script_template % {
+            "module": entry.prefix,
+            "import_name": entry.suffix.split(".")[0],
+            "func": entry.suffix,
+        }
+    # ignore type, because mypy disallows assigning to a method,
+    # see https://github.com/python/mypy/issues/2427
+    maker._get_script_text = _get_script_text  # type: ignore
+    maker.script_template = r"""# -*- coding: utf-8 -*-
+import re
+import sys
+
+from %(module)s import %(import_name)s
+
+if __name__ == '__main__':
+    sys.argv[0] = re.sub(r'(-script\.pyw?|\.exe)?$', '', sys.argv[0])
+    sys.exit(%(func)s())
+"""
+
+    # Special case pip and setuptools to generate versioned wrappers
+    #
+    # The issue is that some projects (specifically, pip and setuptools) use
+    # code in setup.py to create "versioned" entry points - pip2.7 on Python
+    # 2.7, pip3.3 on Python 3.3, etc. But these entry points are baked into
+    # the wheel metadata at build time, and so if the wheel is installed with
+    # a *different* version of Python the entry points will be wrong. The
+    # correct fix for this is to enhance the metadata to be able to describe
+    # such versioned entry points, but that won't happen till Metadata 2.0 is
+    # available.
+    # In the meantime, projects using versioned entry points will either have
+    # incorrect versioned entry points, or they will not be able to distribute
+    # "universal" wheels (i.e., they will need a wheel per Python version).
+    #
+    # Because setuptools and pip are bundled with _ensurepip and virtualenv,
+    # we need to use universal wheels. So, as a stopgap until Metadata 2.0, we
+    # override the versioned entry points in the wheel and generate the
+    # correct ones. This code is purely a short-term measure until Metadata 2.0
+    # is available.
+    #
+    # To add the level of hack in this section of code, in order to support
+    # ensurepip this code will look for an ``ENSUREPIP_OPTIONS`` environment
+    # variable which will control which version scripts get installed.
+    #
+    # ENSUREPIP_OPTIONS=altinstall
+    #   - Only pipX.Y and easy_install-X.Y will be generated and installed
+    # ENSUREPIP_OPTIONS=install
+    #   - pipX.Y, pipX, easy_install-X.Y will be generated and installed. Note
+    #     that this option is technically if ENSUREPIP_OPTIONS is set and is
+    #     not altinstall
+    # DEFAULT
+    #   - The default behavior is to install pip, pipX, pipX.Y, easy_install
+    #     and easy_install-X.Y.
+    pip_script = console.pop('pip', None)
+    if pip_script:
+        if "ENSUREPIP_OPTIONS" not in os.environ:
+            spec = 'pip = ' + pip_script
+            generated.extend(maker.make(spec))
+
+        if os.environ.get("ENSUREPIP_OPTIONS", "") != "altinstall":
+            spec = 'pip%s = %s' % (sys.version[:1], pip_script)
+            generated.extend(maker.make(spec))
+
+        spec = 'pip%s = %s' % (sys.version[:3], pip_script)
+        generated.extend(maker.make(spec))
+        # Delete any other versioned pip entry points
+        pip_ep = [k for k in console if re.match(r'pip(\d(\.\d)?)?$', k)]
+        for k in pip_ep:
+            del console[k]
+    easy_install_script = console.pop('easy_install', None)
+    if easy_install_script:
+        if "ENSUREPIP_OPTIONS" not in os.environ:
+            spec = 'easy_install = ' + easy_install_script
+            generated.extend(maker.make(spec))
+
+        spec = 'easy_install-%s = %s' % (sys.version[:3], easy_install_script)
+        generated.extend(maker.make(spec))
+        # Delete any other versioned easy_install entry points
+        easy_install_ep = [
+            k for k in console if re.match(r'easy_install(-\d\.\d)?$', k)
+        ]
+        for k in easy_install_ep:
+            del console[k]
+
+    # Generate the console and GUI entry points specified in the wheel
+    if len(console) > 0:
+        generated_console_scripts = maker.make_multiple(
+            ['%s = %s' % kv for kv in console.items()]
+        )
+        generated.extend(generated_console_scripts)
+
+        if warn_script_location:
+            msg = message_about_scripts_not_on_PATH(generated_console_scripts)
+            if msg is not None:
+                logger.warning(msg)
+
+    if len(gui) > 0:
+        generated.extend(
+            maker.make_multiple(
+                ['%s = %s' % kv for kv in gui.items()],
+                {'gui': True}
+            )
+        )
+
+    # Record pip as the installer
+    installer = os.path.join(info_dir[0], 'INSTALLER')
+    temp_installer = os.path.join(info_dir[0], 'INSTALLER.pip')
+    with open(temp_installer, 'wb') as installer_file:
+        installer_file.write(b'pip\n')
+    shutil.move(temp_installer, installer)
+    generated.append(installer)
+
+    # Record details of all files installed
+    record = os.path.join(info_dir[0], 'RECORD')
+    temp_record = os.path.join(info_dir[0], 'RECORD.pip')
+    with open_for_csv(record, 'r') as record_in:
+        with open_for_csv(temp_record, 'w+') as record_out:
+            reader = csv.reader(record_in)
+            outrows = get_csv_rows_for_installed(
+                reader, installed=installed, changed=changed,
+                generated=generated, lib_dir=lib_dir,
+            )
+            writer = csv.writer(record_out)
+            # Sort to simplify testing.
+            for row in sorted_outrows(outrows):
+                writer.writerow(row)
+    shutil.move(temp_record, record)
+
+
+def wheel_version(source_dir):
+    # type: (Optional[str]) -> Optional[Tuple[int, ...]]
+    """
+    Return the Wheel-Version of an extracted wheel, if possible.
+
+    Otherwise, return None if we couldn't parse / extract it.
+    """
+    try:
+        dist = [d for d in pkg_resources.find_on_path(None, source_dir)][0]
+
+        wheel_data = dist.get_metadata('WHEEL')
+        wheel_data = Parser().parsestr(wheel_data)
+
+        version = wheel_data['Wheel-Version'].strip()
+        version = tuple(map(int, version.split('.')))
+        return version
+    except Exception:
+        return None
+
+
+def check_compatibility(version, name):
+    # type: (Optional[Tuple[int, ...]], str) -> None
+    """
+    Raises errors or warns if called with an incompatible Wheel-Version.
+
+    Pip should refuse to install a Wheel-Version that's a major series
+    ahead of what it's compatible with (e.g 2.0 > 1.1); and warn when
+    installing a version only minor version ahead (e.g 1.2 > 1.1).
+
+    version: a 2-tuple representing a Wheel-Version (Major, Minor)
+    name: name of wheel or package to raise exception about
+
+    :raises UnsupportedWheel: when an incompatible Wheel-Version is given
+    """
+    if not version:
+        raise UnsupportedWheel(
+            "%s is in an unsupported or invalid wheel" % name
+        )
+    if version[0] > VERSION_COMPATIBLE[0]:
+        raise UnsupportedWheel(
+            "%s's Wheel-Version (%s) is not compatible with this version "
+            "of pip" % (name, '.'.join(map(str, version)))
+        )
+    elif version > VERSION_COMPATIBLE:
+        logger.warning(
+            'Installing from a newer Wheel-Version (%s)',
+            '.'.join(map(str, version)),
+        )
+
+
+def format_tag(file_tag):
+    # type: (Tuple[str, ...]) -> str
+    """
+    Format three tags in the form "<python_tag>-<abi_tag>-<platform_tag>".
+
+    :param file_tag: A 3-tuple of tags (python_tag, abi_tag, platform_tag).
+    """
+    return '-'.join(file_tag)
+
+
+class Wheel(object):
+    """A wheel file"""
+
+    # TODO: Maybe move the class into the models sub-package
+    # TODO: Maybe move the install code into this class
+
+    wheel_file_re = re.compile(
+        r"""^(?P<namever>(?P<name>.+?)-(?P<ver>.*?))
+        ((-(?P<build>\d[^-]*?))?-(?P<pyver>.+?)-(?P<abi>.+?)-(?P<plat>.+?)
+        \.whl|\.dist-info)$""",
+        re.VERBOSE
+    )
+
+    def __init__(self, filename):
+        # type: (str) -> None
+        """
+        :raises InvalidWheelFilename: when the filename is invalid for a wheel
+        """
+        wheel_info = self.wheel_file_re.match(filename)
+        if not wheel_info:
+            raise InvalidWheelFilename(
+                "%s is not a valid wheel filename." % filename
+            )
+        self.filename = filename
+        self.name = wheel_info.group('name').replace('_', '-')
+        # we'll assume "_" means "-" due to wheel naming scheme
+        # (https://github.com/pypa/pip/issues/1150)
+        self.version = wheel_info.group('ver').replace('_', '-')
+        self.build_tag = wheel_info.group('build')
+        self.pyversions = wheel_info.group('pyver').split('.')
+        self.abis = wheel_info.group('abi').split('.')
+        self.plats = wheel_info.group('plat').split('.')
+
+        # All the tag combinations from this file
+        self.file_tags = {
+            (x, y, z) for x in self.pyversions
+            for y in self.abis for z in self.plats
+        }
+
+    def get_formatted_file_tags(self):
+        # type: () -> List[str]
+        """
+        Return the wheel's tags as a sorted list of strings.
+        """
+        return sorted(format_tag(tag) for tag in self.file_tags)
+
+    def support_index_min(self, tags=None):
+        # type: (Optional[List[Pep425Tag]]) -> Optional[int]
+        """
+        Return the lowest index that one of the wheel's file_tag combinations
+        achieves in the supported_tags list e.g. if there are 8 supported tags,
+        and one of the file tags is first in the list, then return 0.  Returns
+        None is the wheel is not supported.
+        """
+        if tags is None:  # for mock
+            tags = pep425tags.get_supported()
+        indexes = [tags.index(c) for c in self.file_tags if c in tags]
+        return min(indexes) if indexes else None
+
+    def supported(self, tags=None):
+        # type: (Optional[List[Pep425Tag]]) -> bool
+        """Is this wheel supported on this system?"""
+        if tags is None:  # for mock
+            tags = pep425tags.get_supported()
+        return bool(set(tags).intersection(self.file_tags))
+
+
+def _contains_egg_info(
+        s, _egg_info_re=re.compile(r'([a-z0-9_.]+)-([a-z0-9_.!+-]+)', re.I)):
+    """Determine whether the string looks like an egg_info.
+
+    :param s: The string to parse. E.g. foo-2.1
+    """
+    return bool(_egg_info_re.search(s))
+
+
+def should_use_ephemeral_cache(
+    req,  # type: InstallRequirement
+    format_control,  # type: FormatControl
+    autobuilding,  # type: bool
+    cache_available  # type: bool
+):
+    # type: (...) -> Optional[bool]
+    """
+    Return whether to build an InstallRequirement object using the
+    ephemeral cache.
+
+    :param cache_available: whether a cache directory is available for the
+        autobuilding=True case.
+
+    :return: True or False to build the requirement with ephem_cache=True
+        or False, respectively; or None not to build the requirement.
+    """
+    if req.constraint:
+        return None
+    if req.is_wheel:
+        if not autobuilding:
+            logger.info(
+                'Skipping %s, due to already being wheel.', req.name,
+            )
+        return None
+    if not autobuilding:
+        return False
+
+    if req.editable or not req.source_dir:
+        return None
+
+    if "binary" not in format_control.get_allowed_formats(
+            canonicalize_name(req.name)):
+        logger.info(
+            "Skipping bdist_wheel for %s, due to binaries "
+            "being disabled for it.", req.name,
+        )
+        return None
+
+    if req.link and not req.link.is_artifact:
+        # VCS checkout. Build wheel just for this run.
+        return True
+
+    link = req.link
+    base, ext = link.splitext()
+    if cache_available and _contains_egg_info(base):
+        return False
+
+    # Otherwise, build the wheel just for this run using the ephemeral
+    # cache since we are either in the case of e.g. a local directory, or
+    # no cache directory is available to use.
+    return True
+
+
+def format_command_result(
+    command_args,  # type: List[str]
+    command_output,  # type: str
+):
+    # type: (...) -> str
+    """
+    Format command information for logging.
+    """
+    command_desc = format_command_args(command_args)
+    text = 'Command arguments: {}\n'.format(command_desc)
+
+    if not command_output:
+        text += 'Command output: None'
+    elif logger.getEffectiveLevel() > logging.DEBUG:
+        text += 'Command output: [use --verbose to show]'
+    else:
+        if not command_output.endswith('\n'):
+            command_output += '\n'
+        text += 'Command output:\n{}{}'.format(command_output, LOG_DIVIDER)
+
+    return text
+
+
+def get_legacy_build_wheel_path(
+    names,  # type: List[str]
+    temp_dir,  # type: str
+    req,  # type: InstallRequirement
+    command_args,  # type: List[str]
+    command_output,  # type: str
+):
+    # type: (...) -> Optional[str]
+    """
+    Return the path to the wheel in the temporary build directory.
+    """
+    # Sort for determinism.
+    names = sorted(names)
+    if not names:
+        msg = (
+            'Legacy build of wheel for {!r} created no files.\n'
+        ).format(req.name)
+        msg += format_command_result(command_args, command_output)
+        logger.warning(msg)
+        return None
+
+    if len(names) > 1:
+        msg = (
+            'Legacy build of wheel for {!r} created more than one file.\n'
+            'Filenames (choosing first): {}\n'
+        ).format(req.name, names)
+        msg += format_command_result(command_args, command_output)
+        logger.warning(msg)
+
+    return os.path.join(temp_dir, names[0])
+
+
+class WheelBuilder(object):
+    """Build wheels from a RequirementSet."""
+
+    def __init__(
+        self,
+        finder,  # type: PackageFinder
+        preparer,  # type: RequirementPreparer
+        wheel_cache,  # type: WheelCache
+        build_options=None,  # type: Optional[List[str]]
+        global_options=None,  # type: Optional[List[str]]
+        no_clean=False  # type: bool
+    ):
+        # type: (...) -> None
+        self.finder = finder
+        self.preparer = preparer
+        self.wheel_cache = wheel_cache
+
+        self._wheel_dir = preparer.wheel_download_dir
+
+        self.build_options = build_options or []
+        self.global_options = global_options or []
+        self.no_clean = no_clean
+
+    def _build_one(self, req, output_dir, python_tag=None):
+        """Build one wheel.
+
+        :return: The filename of the built wheel, or None if the build failed.
+        """
+        # Install build deps into temporary directory (PEP 518)
+        with req.build_env:
+            return self._build_one_inside_env(req, output_dir,
+                                              python_tag=python_tag)
+
+    def _build_one_inside_env(self, req, output_dir, python_tag=None):
+        with TempDirectory(kind="wheel") as temp_dir:
+            if req.use_pep517:
+                builder = self._build_one_pep517
+            else:
+                builder = self._build_one_legacy
+            wheel_path = builder(req, temp_dir.path, python_tag=python_tag)
+            if wheel_path is not None:
+                wheel_name = os.path.basename(wheel_path)
+                dest_path = os.path.join(output_dir, wheel_name)
+                try:
+                    wheel_hash, length = hash_file(wheel_path)
+                    shutil.move(wheel_path, dest_path)
+                    logger.info('Created wheel for %s: '
+                                'filename=%s size=%d sha256=%s',
+                                req.name, wheel_name, length,
+                                wheel_hash.hexdigest())
+                    logger.info('Stored in directory: %s', output_dir)
+                    return dest_path
+                except Exception:
+                    pass
+            # Ignore return, we can't do anything else useful.
+            self._clean_one(req)
+            return None
+
+    def _base_setup_args(self, req):
+        # NOTE: Eventually, we'd want to also -S to the flags here, when we're
+        # isolating. Currently, it breaks Python in virtualenvs, because it
+        # relies on site.py to find parts of the standard library outside the
+        # virtualenv.
+        base_cmd = make_setuptools_shim_args(req.setup_py_path,
+                                             unbuffered_output=True)
+        return base_cmd + list(self.global_options)
+
+    def _build_one_pep517(self, req, tempd, python_tag=None):
+        """Build one InstallRequirement using the PEP 517 build process.
+
+        Returns path to wheel if successfully built. Otherwise, returns None.
+        """
+        assert req.metadata_directory is not None
+        if self.build_options:
+            # PEP 517 does not support --build-options
+            logger.error('Cannot build wheel for %s using PEP 517 when '
+                         '--build-options is present' % (req.name,))
+            return None
+        try:
+            req.spin_message = 'Building wheel for %s (PEP 517)' % (req.name,)
+            logger.debug('Destination directory: %s', tempd)
+            wheel_name = req.pep517_backend.build_wheel(
+                tempd,
+                metadata_directory=req.metadata_directory
+            )
+            if python_tag:
+                # General PEP 517 backends don't necessarily support
+                # a "--python-tag" option, so we rename the wheel
+                # file directly.
+                new_name = replace_python_tag(wheel_name, python_tag)
+                os.rename(
+                    os.path.join(tempd, wheel_name),
+                    os.path.join(tempd, new_name)
+                )
+                # Reassign to simplify the return at the end of function
+                wheel_name = new_name
+        except Exception:
+            logger.error('Failed building wheel for %s', req.name)
+            return None
+        return os.path.join(tempd, wheel_name)
+
+    def _build_one_legacy(self, req, tempd, python_tag=None):
+        """Build one InstallRequirement using the "legacy" build process.
+
+        Returns path to wheel if successfully built. Otherwise, returns None.
+        """
+        base_args = self._base_setup_args(req)
+
+        spin_message = 'Building wheel for %s (setup.py)' % (req.name,)
+        with open_spinner(spin_message) as spinner:
+            logger.debug('Destination directory: %s', tempd)
+            wheel_args = base_args + ['bdist_wheel', '-d', tempd] \
+                + self.build_options
+
+            if python_tag is not None:
+                wheel_args += ["--python-tag", python_tag]
+
+            try:
+                output = call_subprocess(wheel_args, cwd=req.setup_py_dir,
+                                         spinner=spinner)
+            except Exception:
+                spinner.finish("error")
+                logger.error('Failed building wheel for %s', req.name)
+                return None
+            names = os.listdir(tempd)
+            wheel_path = get_legacy_build_wheel_path(
+                names=names,
+                temp_dir=tempd,
+                req=req,
+                command_args=wheel_args,
+                command_output=output,
+            )
+            return wheel_path
+
+    def _clean_one(self, req):
+        base_args = self._base_setup_args(req)
+
+        logger.info('Running setup.py clean for %s', req.name)
+        clean_args = base_args + ['clean', '--all']
+        try:
+            call_subprocess(clean_args, cwd=req.source_dir)
+            return True
+        except Exception:
+            logger.error('Failed cleaning build dir for %s', req.name)
+            return False
+
+    def build(
+        self,
+        requirements,  # type: Iterable[InstallRequirement]
+        session,  # type: PipSession
+        autobuilding=False  # type: bool
+    ):
+        # type: (...) -> List[InstallRequirement]
+        """Build wheels.
+
+        :param unpack: If True, replace the sdist we built from with the
+            newly built wheel, in preparation for installation.
+        :return: True if all the wheels built correctly.
+        """
+        buildset = []
+        format_control = self.finder.format_control
+        # Whether a cache directory is available for autobuilding=True.
+        cache_available = bool(self._wheel_dir or self.wheel_cache.cache_dir)
+
+        for req in requirements:
+            ephem_cache = should_use_ephemeral_cache(
+                req, format_control=format_control, autobuilding=autobuilding,
+                cache_available=cache_available,
+            )
+            if ephem_cache is None:
+                continue
+
+            buildset.append((req, ephem_cache))
+
+        if not buildset:
+            return []
+
+        # Is any wheel build not using the ephemeral cache?
+        if any(not ephem_cache for _, ephem_cache in buildset):
+            have_directory_for_build = self._wheel_dir or (
+                autobuilding and self.wheel_cache.cache_dir
+            )
+            assert have_directory_for_build
+
+        # TODO by @pradyunsg
+        # Should break up this method into 2 separate methods.
+
+        # Build the wheels.
+        logger.info(
+            'Building wheels for collected packages: %s',
+            ', '.join([req.name for (req, _) in buildset]),
+        )
+        _cache = self.wheel_cache  # shorter name
+        with indent_log():
+            build_success, build_failure = [], []
+            for req, ephem in buildset:
+                python_tag = None
+                if autobuilding:
+                    python_tag = pep425tags.implementation_tag
+                    if ephem:
+                        output_dir = _cache.get_ephem_path_for_link(req.link)
+                    else:
+                        output_dir = _cache.get_path_for_link(req.link)
+                    try:
+                        ensure_dir(output_dir)
+                    except OSError as e:
+                        logger.warning("Building wheel for %s failed: %s",
+                                       req.name, e)
+                        build_failure.append(req)
+                        continue
+                else:
+                    output_dir = self._wheel_dir
+                wheel_file = self._build_one(
+                    req, output_dir,
+                    python_tag=python_tag,
+                )
+                if wheel_file:
+                    build_success.append(req)
+                    if autobuilding:
+                        # XXX: This is mildly duplicative with prepare_files,
+                        # but not close enough to pull out to a single common
+                        # method.
+                        # The code below assumes temporary source dirs -
+                        # prevent it doing bad things.
+                        if req.source_dir and not os.path.exists(os.path.join(
+                                req.source_dir, PIP_DELETE_MARKER_FILENAME)):
+                            raise AssertionError(
+                                "bad source dir - missing marker")
+                        # Delete the source we built the wheel from
+                        req.remove_temporary_source()
+                        # set the build directory again - name is known from
+                        # the work prepare_files did.
+                        req.source_dir = req.build_location(
+                            self.preparer.build_dir
+                        )
+                        # Update the link for this.
+                        req.link = Link(path_to_url(wheel_file))
+                        assert req.link.is_wheel
+                        # extract the wheel into the dir
+                        unpack_url(
+                            req.link, req.source_dir, None, False,
+                            session=session,
+                        )
+                else:
+                    build_failure.append(req)
+
+        # notify success/failure
+        if build_success:
+            logger.info(
+                'Successfully built %s',
+                ' '.join([req.name for req in build_success]),
+            )
+        if build_failure:
+            logger.info(
+                'Failed to build %s',
+                ' '.join([req.name for req in build_failure]),
+            )
+        # Return a list of requirements that failed to build
+        return build_failure