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Lib/site-packages/virtualenv/seed/wheels/__init__.py

@@ -0,0 +1,11 @@
+from __future__ import absolute_import, unicode_literals
+
+from .acquire import get_wheel, pip_wheel_env_run
+from .util import Version, Wheel
+
+__all__ = (
+    "get_wheel",
+    "pip_wheel_env_run",
+    "Version",
+    "Wheel",
+)

Lib/site-packages/virtualenv/seed/wheels/acquire.py

@@ -0,0 +1,120 @@
+"""Bootstrap"""
+from __future__ import absolute_import, unicode_literals
+
+import logging
+import os
+import sys
+from operator import eq, lt
+
+from virtualenv.util.path import Path
+from virtualenv.util.six import ensure_str
+from virtualenv.util.subprocess import Popen, subprocess
+
+from .bundle import from_bundle
+from .util import Version, Wheel, discover_wheels
+
+
+def get_wheel(distribution, version, for_py_version, search_dirs, download, app_data, do_periodic_update):
+    """
+    Get a wheel with the given distribution-version-for_py_version trio, by using the extra search dir + download
+    """
+    # not all wheels are compatible with all python versions, so we need to py version qualify it
+    # 1. acquire from bundle
+    wheel = from_bundle(distribution, version, for_py_version, search_dirs, app_data, do_periodic_update)
+
+    # 2. download from the internet
+    if version not in Version.non_version and download:
+        wheel = download_wheel(
+            distribution=distribution,
+            version_spec=Version.as_version_spec(version),
+            for_py_version=for_py_version,
+            search_dirs=search_dirs,
+            app_data=app_data,
+            to_folder=app_data.house,
+        )
+    return wheel
+
+
+def download_wheel(distribution, version_spec, for_py_version, search_dirs, app_data, to_folder):
+    to_download = "{}{}".format(distribution, version_spec or "")
+    logging.debug("download wheel %s %s to %s", to_download, for_py_version, to_folder)
+    cmd = [
+        sys.executable,
+        "-m",
+        "pip",
+        "download",
+        "--progress-bar",
+        "off",
+        "--disable-pip-version-check",
+        "--only-binary=:all:",
+        "--no-deps",
+        "--python-version",
+        for_py_version,
+        "-d",
+        str(to_folder),
+        to_download,
+    ]
+    # pip has no interface in python - must be a new sub-process
+    env = pip_wheel_env_run(search_dirs, app_data)
+    process = Popen(cmd, env=env, stdout=subprocess.PIPE, stderr=subprocess.PIPE, universal_newlines=True)
+    out, err = process.communicate()
+    if process.returncode != 0:
+        kwargs = {"output": out}
+        if sys.version_info < (3, 5):
+            kwargs["output"] += err
+        else:
+            kwargs["stderr"] = err
+        raise subprocess.CalledProcessError(process.returncode, cmd, **kwargs)
+    result = _find_downloaded_wheel(distribution, version_spec, for_py_version, to_folder, out)
+    logging.debug("downloaded wheel %s", result.name)
+    return result
+
+
+def _find_downloaded_wheel(distribution, version_spec, for_py_version, to_folder, out):
+    for line in out.splitlines():
+        line = line.lstrip()
+        for marker in ("Saved ", "File was already downloaded "):
+            if line.startswith(marker):
+                return Wheel(Path(line[len(marker) :]).absolute())
+    # if for some reason the output does not match fallback to latest version with that spec
+    return find_compatible_in_house(distribution, version_spec, for_py_version, to_folder)
+
+
+def find_compatible_in_house(distribution, version_spec, for_py_version, in_folder):
+    wheels = discover_wheels(in_folder, distribution, None, for_py_version)
+    start, end = 0, len(wheels)
+    if version_spec is not None:
+        if version_spec.startswith("<"):
+            from_pos, op = 1, lt
+        elif version_spec.startswith("=="):
+            from_pos, op = 2, eq
+        else:
+            raise ValueError(version_spec)
+        version = Wheel.as_version_tuple(version_spec[from_pos:])
+        start = next((at for at, w in enumerate(wheels) if op(w.version_tuple, version)), len(wheels))
+
+    return None if start == end else wheels[start]
+
+
+def pip_wheel_env_run(search_dirs, app_data):
+    for_py_version = "{}.{}".format(*sys.version_info[0:2])
+    env = os.environ.copy()
+    env.update(
+        {
+            ensure_str(k): str(v)  # python 2 requires these to be string only (non-unicode)
+            for k, v in {"PIP_USE_WHEEL": "1", "PIP_USER": "0", "PIP_NO_INPUT": "1"}.items()
+        },
+    )
+    wheel = get_wheel(
+        distribution="pip",
+        version=None,
+        for_py_version=for_py_version,
+        search_dirs=search_dirs,
+        download=False,
+        app_data=app_data,
+        do_periodic_update=False,
+    )
+    if wheel is None:
+        raise RuntimeError("could not find the embedded pip")
+    env[str("PYTHONPATH")] = str(wheel.path)
+    return env

Lib/site-packages/virtualenv/seed/wheels/bundle.py

@@ -0,0 +1,51 @@
+from __future__ import absolute_import, unicode_literals
+
+from virtualenv.app_data import AppDataDiskFolder, TempAppData
+
+from ..wheels.embed import get_embed_wheel
+from .periodic_update import periodic_update
+from .util import Version, Wheel, discover_wheels
+
+
+def from_bundle(distribution, version, for_py_version, search_dirs, app_data, do_periodic_update):
+    """
+    Load the bundled wheel to a cache directory.
+    """
+    of_version = Version.of_version(version)
+    wheel = load_embed_wheel(app_data, distribution, for_py_version, of_version)
+
+    if version != Version.embed:
+        # 2. check if we have upgraded embed
+        if isinstance(app_data, AppDataDiskFolder) and not isinstance(app_data, TempAppData):
+            wheel = periodic_update(distribution, for_py_version, wheel, search_dirs, app_data, do_periodic_update)
+
+        # 3. acquire from extra search dir
+        found_wheel = from_dir(distribution, of_version, for_py_version, search_dirs)
+        if found_wheel is not None:
+            if wheel is None:
+                wheel = found_wheel
+            elif found_wheel.version_tuple > wheel.version_tuple:
+                wheel = found_wheel
+    return wheel
+
+
+def load_embed_wheel(app_data, distribution, for_py_version, version):
+    wheel = get_embed_wheel(distribution, for_py_version)
+    if wheel is not None:
+        version_match = version == wheel.version
+        if version is None or version_match:
+            with app_data.ensure_extracted(wheel.path, lambda: app_data.house) as wheel_path:
+                wheel = Wheel(wheel_path)
+        else:  # if version does not match ignore
+            wheel = None
+    return wheel
+
+
+def from_dir(distribution, version, for_py_version, directories):
+    """
+    Load a compatible wheel from a given folder.
+    """
+    for folder in directories:
+        for wheel in discover_wheels(folder, distribution, version, for_py_version):
+            return wheel
+    return None

Lib/site-packages/virtualenv/seed/wheels/embed/__init__.py

@@ -0,0 +1,62 @@
+from __future__ import absolute_import, unicode_literals
+
+from virtualenv.seed.wheels.util import Wheel
+from virtualenv.util.path import Path
+
+BUNDLE_FOLDER = Path(__file__).absolute().parent
+BUNDLE_SUPPORT = {
+    "3.10": {
+        "pip": "pip-20.2.3-py2.py3-none-any.whl",
+        "setuptools": "setuptools-50.3.1-py3-none-any.whl",
+        "wheel": "wheel-0.35.1-py2.py3-none-any.whl",
+    },
+    "3.9": {
+        "pip": "pip-20.2.3-py2.py3-none-any.whl",
+        "setuptools": "setuptools-50.3.1-py3-none-any.whl",
+        "wheel": "wheel-0.35.1-py2.py3-none-any.whl",
+    },
+    "3.8": {
+        "pip": "pip-20.2.3-py2.py3-none-any.whl",
+        "setuptools": "setuptools-50.3.1-py3-none-any.whl",
+        "wheel": "wheel-0.35.1-py2.py3-none-any.whl",
+    },
+    "3.7": {
+        "pip": "pip-20.2.3-py2.py3-none-any.whl",
+        "setuptools": "setuptools-50.3.1-py3-none-any.whl",
+        "wheel": "wheel-0.35.1-py2.py3-none-any.whl",
+    },
+    "3.6": {
+        "pip": "pip-20.2.3-py2.py3-none-any.whl",
+        "setuptools": "setuptools-50.3.1-py3-none-any.whl",
+        "wheel": "wheel-0.35.1-py2.py3-none-any.whl",
+    },
+    "3.5": {
+        "pip": "pip-20.2.3-py2.py3-none-any.whl",
+        "setuptools": "setuptools-50.3.1-py3-none-any.whl",
+        "wheel": "wheel-0.35.1-py2.py3-none-any.whl",
+    },
+    "3.4": {
+        "pip": "pip-19.1.1-py2.py3-none-any.whl",
+        "setuptools": "setuptools-43.0.0-py2.py3-none-any.whl",
+        "wheel": "wheel-0.33.6-py2.py3-none-any.whl",
+    },
+    "2.7": {
+        "pip": "pip-20.2.3-py2.py3-none-any.whl",
+        "setuptools": "setuptools-44.1.1-py2.py3-none-any.whl",
+        "wheel": "wheel-0.35.1-py2.py3-none-any.whl",
+    },
+}
+MAX = "3.10"
+
+
+def get_embed_wheel(distribution, for_py_version):
+    path = BUNDLE_FOLDER / (BUNDLE_SUPPORT.get(for_py_version, {}) or BUNDLE_SUPPORT[MAX]).get(distribution)
+    return Wheel.from_path(path)
+
+
+__all__ = (
+    "get_embed_wheel",
+    "BUNDLE_SUPPORT",
+    "MAX",
+    "BUNDLE_FOLDER",
+)

Lib/site-packages/virtualenv/seed/wheels/periodic_update.py

@@ -0,0 +1,367 @@
+"""
+Periodically update bundled versions.
+"""
+
+from __future__ import absolute_import, unicode_literals
+
+import json
+import logging
+import os
+import ssl
+import subprocess
+import sys
+from datetime import datetime, timedelta
+from itertools import groupby
+from shutil import copy2
+from textwrap import dedent
+from threading import Thread
+
+from six.moves.urllib.error import URLError
+from six.moves.urllib.request import urlopen
+
+from virtualenv.app_data import AppDataDiskFolder
+from virtualenv.info import PY2
+from virtualenv.util.path import Path
+from virtualenv.util.subprocess import CREATE_NO_WINDOW, Popen
+
+from ..wheels.embed import BUNDLE_SUPPORT
+from ..wheels.util import Wheel
+
+if PY2:
+    # on Python 2 datetime.strptime throws the error below if the import did not trigger on main thread
+    # Failed to import _strptime because the import lock is held by
+    try:
+        import _strptime  # noqa
+    except ImportError:  # pragma: no cov
+        pass  # pragma: no cov
+
+
+def periodic_update(distribution, for_py_version, wheel, search_dirs, app_data, do_periodic_update):
+    if do_periodic_update:
+        handle_auto_update(distribution, for_py_version, wheel, search_dirs, app_data)
+
+    now = datetime.now()
+
+    u_log = UpdateLog.from_app_data(app_data, distribution, for_py_version)
+    u_log_older_than_hour = now - u_log.completed > timedelta(hours=1) if u_log.completed is not None else False
+    for _, group in groupby(u_log.versions, key=lambda v: v.wheel.version_tuple[0:2]):
+        version = next(group)  # use only latest patch version per minor, earlier assumed to be buggy
+        if wheel is not None and Path(version.filename).name == wheel.name:
+            break
+        if u_log.periodic is False or (u_log_older_than_hour and version.use(now)):
+            updated_wheel = Wheel(app_data.house / version.filename)
+            logging.debug("using %supdated wheel %s", "periodically " if updated_wheel else "", updated_wheel)
+            wheel = updated_wheel
+            break
+
+    return wheel
+
+
+def handle_auto_update(distribution, for_py_version, wheel, search_dirs, app_data):
+    embed_update_log = app_data.embed_update_log(distribution, for_py_version)
+    u_log = UpdateLog.from_dict(embed_update_log.read())
+    if u_log.needs_update:
+        u_log.periodic = True
+        u_log.started = datetime.now()
+        embed_update_log.write(u_log.to_dict())
+        trigger_update(distribution, for_py_version, wheel, search_dirs, app_data, periodic=True)
+
+
+DATETIME_FMT = "%Y-%m-%dT%H:%M:%S.%fZ"
+
+
+def dump_datetime(value):
+    return None if value is None else value.strftime(DATETIME_FMT)
+
+
+def load_datetime(value):
+    return None if value is None else datetime.strptime(value, DATETIME_FMT)
+
+
+class NewVersion(object):
+    def __init__(self, filename, found_date, release_date):
+        self.filename = filename
+        self.found_date = found_date
+        self.release_date = release_date
+
+    @classmethod
+    def from_dict(cls, dictionary):
+        return cls(
+            filename=dictionary["filename"],
+            found_date=load_datetime(dictionary["found_date"]),
+            release_date=load_datetime(dictionary["release_date"]),
+        )
+
+    def to_dict(self):
+        return {
+            "filename": self.filename,
+            "release_date": dump_datetime(self.release_date),
+            "found_date": dump_datetime(self.found_date),
+        }
+
+    def use(self, now):
+        compare_from = self.release_date or self.found_date
+        return now - compare_from >= timedelta(days=28)
+
+    def __repr__(self):
+        return "{}(filename={}), found_date={}, release_date={})".format(
+            self.__class__.__name__,
+            self.filename,
+            self.found_date,
+            self.release_date,
+        )
+
+    def __eq__(self, other):
+        return type(self) == type(other) and all(
+            getattr(self, k) == getattr(other, k) for k in ["filename", "release_date", "found_date"]
+        )
+
+    def __ne__(self, other):
+        return not (self == other)
+
+    @property
+    def wheel(self):
+        return Wheel(Path(self.filename))
+
+
+class UpdateLog(object):
+    def __init__(self, started, completed, versions, periodic):
+        self.started = started
+        self.completed = completed
+        self.versions = versions
+        self.periodic = periodic
+
+    @classmethod
+    def from_dict(cls, dictionary):
+        if dictionary is None:
+            dictionary = {}
+        return cls(
+            load_datetime(dictionary.get("started")),
+            load_datetime(dictionary.get("completed")),
+            [NewVersion.from_dict(v) for v in dictionary.get("versions", [])],
+            dictionary.get("periodic"),
+        )
+
+    @classmethod
+    def from_app_data(cls, app_data, distribution, for_py_version):
+        raw_json = app_data.embed_update_log(distribution, for_py_version).read()
+        return cls.from_dict(raw_json)
+
+    def to_dict(self):
+        return {
+            "started": dump_datetime(self.started),
+            "completed": dump_datetime(self.completed),
+            "periodic": self.periodic,
+            "versions": [r.to_dict() for r in self.versions],
+        }
+
+    @property
+    def needs_update(self):
+        now = datetime.now()
+        if self.completed is None:  # never completed
+            return self._check_start(now)
+        else:
+            if now - self.completed <= timedelta(days=14):
+                return False
+            return self._check_start(now)
+
+    def _check_start(self, now):
+        return self.started is None or now - self.started > timedelta(hours=1)
+
+
+def trigger_update(distribution, for_py_version, wheel, search_dirs, app_data, periodic):
+    wheel_path = None if wheel is None else str(wheel.path)
+    cmd = [
+        sys.executable,
+        "-c",
+        dedent(
+            """
+        from virtualenv.report import setup_report, MAX_LEVEL
+        from virtualenv.seed.wheels.periodic_update import do_update
+        setup_report(MAX_LEVEL, show_pid=True)
+        do_update({!r}, {!r}, {!r}, {!r}, {!r}, {!r})
+        """,
+        )
+        .strip()
+        .format(distribution, for_py_version, wheel_path, str(app_data), [str(p) for p in search_dirs], periodic),
+    ]
+    debug = os.environ.get(str("_VIRTUALENV_PERIODIC_UPDATE_INLINE")) == str("1")
+    pipe = None if debug else subprocess.PIPE
+    kwargs = {"stdout": pipe, "stderr": pipe}
+    if not debug and sys.platform == "win32":
+        kwargs["creationflags"] = CREATE_NO_WINDOW
+    process = Popen(cmd, **kwargs)
+    logging.info(
+        "triggered periodic upgrade of %s%s (for python %s) via background process having PID %d",
+        distribution,
+        "" if wheel is None else "=={}".format(wheel.version),
+        for_py_version,
+        process.pid,
+    )
+    if debug:
+        process.communicate()  # on purpose not called to make it a background process
+
+
+def do_update(distribution, for_py_version, embed_filename, app_data, search_dirs, periodic):
+    versions = None
+    try:
+        versions = _run_do_update(app_data, distribution, embed_filename, for_py_version, periodic, search_dirs)
+    finally:
+        logging.debug("done %s %s with %s", distribution, for_py_version, versions)
+    return versions
+
+
+def _run_do_update(app_data, distribution, embed_filename, for_py_version, periodic, search_dirs):
+    from virtualenv.seed.wheels import acquire
+
+    wheel_filename = None if embed_filename is None else Path(embed_filename)
+    embed_version = None if wheel_filename is None else Wheel(wheel_filename).version_tuple
+    app_data = AppDataDiskFolder(app_data) if isinstance(app_data, str) else app_data
+    search_dirs = [Path(p) if isinstance(p, str) else p for p in search_dirs]
+    wheelhouse = app_data.house
+    embed_update_log = app_data.embed_update_log(distribution, for_py_version)
+    u_log = UpdateLog.from_dict(embed_update_log.read())
+    now = datetime.now()
+    if wheel_filename is not None:
+        dest = wheelhouse / wheel_filename.name
+        if not dest.exists():
+            copy2(str(wheel_filename), str(wheelhouse))
+    last, last_version, versions = None, None, []
+    while last is None or not last.use(now):
+        download_time = datetime.now()
+        dest = acquire.download_wheel(
+            distribution=distribution,
+            version_spec=None if last_version is None else "<{}".format(last_version),
+            for_py_version=for_py_version,
+            search_dirs=search_dirs,
+            app_data=app_data,
+            to_folder=wheelhouse,
+        )
+        if dest is None or (u_log.versions and u_log.versions[0].filename == dest.name):
+            break
+        release_date = release_date_for_wheel_path(dest.path)
+        last = NewVersion(filename=dest.path.name, release_date=release_date, found_date=download_time)
+        logging.info("detected %s in %s", last, datetime.now() - download_time)
+        versions.append(last)
+        last_wheel = Wheel(Path(last.filename))
+        last_version = last_wheel.version
+        if embed_version is not None:
+            if embed_version >= last_wheel.version_tuple:  # stop download if we reach the embed version
+                break
+    u_log.periodic = periodic
+    if not u_log.periodic:
+        u_log.started = now
+    u_log.versions = versions + u_log.versions
+    u_log.completed = datetime.now()
+    embed_update_log.write(u_log.to_dict())
+    return versions
+
+
+def release_date_for_wheel_path(dest):
+    wheel = Wheel(dest)
+    # the most accurate is to ask PyPi - e.g. https://pypi.org/pypi/pip/json,
+    # see https://warehouse.pypa.io/api-reference/json/ for more details
+    content = _pypi_get_distribution_info_cached(wheel.distribution)
+    if content is not None:
+        try:
+            upload_time = content["releases"][wheel.version][0]["upload_time"]
+            return datetime.strptime(upload_time, "%Y-%m-%dT%H:%M:%S")
+        except Exception as exception:
+            logging.error("could not load release date %s because %r", content, exception)
+    return None
+
+
+def _request_context():
+    yield None
+    # fallback to non verified HTTPS (the information we request is not sensitive, so fallback)
+    yield ssl._create_unverified_context()  # noqa
+
+
+_PYPI_CACHE = {}
+
+
+def _pypi_get_distribution_info_cached(distribution):
+    if distribution not in _PYPI_CACHE:
+        _PYPI_CACHE[distribution] = _pypi_get_distribution_info(distribution)
+    return _PYPI_CACHE[distribution]
+
+
+def _pypi_get_distribution_info(distribution):
+    content, url = None, "https://pypi.org/pypi/{}/json".format(distribution)
+    try:
+        for context in _request_context():
+            try:
+                with urlopen(url, context=context) as file_handler:
+                    content = json.load(file_handler)
+                break
+            except URLError as exception:
+                logging.error("failed to access %s because %r", url, exception)
+    except Exception as exception:
+        logging.error("failed to access %s because %r", url, exception)
+    return content
+
+
+def manual_upgrade(app_data):
+    threads = []
+
+    for for_py_version, distribution_to_package in BUNDLE_SUPPORT.items():
+        # load extra search dir for the given for_py
+        for distribution in distribution_to_package.keys():
+            thread = Thread(target=_run_manual_upgrade, args=(app_data, distribution, for_py_version))
+            thread.start()
+            threads.append(thread)
+
+    for thread in threads:
+        thread.join()
+
+
+def _run_manual_upgrade(app_data, distribution, for_py_version):
+    start = datetime.now()
+    from .bundle import from_bundle
+
+    current = from_bundle(
+        distribution=distribution,
+        version=None,
+        for_py_version=for_py_version,
+        search_dirs=[],
+        app_data=app_data,
+        do_periodic_update=False,
+    )
+    logging.warning(
+        "upgrade %s for python %s with current %s",
+        distribution,
+        for_py_version,
+        "" if current is None else current.name,
+    )
+    versions = do_update(
+        distribution=distribution,
+        for_py_version=for_py_version,
+        embed_filename=current.path,
+        app_data=app_data,
+        search_dirs=[],
+        periodic=False,
+    )
+    msg = "upgraded %s for python %s in %s {}".format(
+        "new entries found:\n%s" if versions else "no new versions found",
+    )
+    args = [
+        distribution,
+        for_py_version,
+        datetime.now() - start,
+    ]
+    if versions:
+        args.append("\n".join("\t{}".format(v) for v in versions))
+    logging.warning(msg, *args)
+
+
+__all__ = (
+    "periodic_update",
+    "do_update",
+    "manual_upgrade",
+    "NewVersion",
+    "UpdateLog",
+    "load_datetime",
+    "dump_datetime",
+    "trigger_update",
+    "release_date_for_wheel_path",
+)

Lib/site-packages/virtualenv/seed/wheels/util.py

@@ -0,0 +1,116 @@
+from __future__ import absolute_import, unicode_literals
+
+from operator import attrgetter
+from zipfile import ZipFile
+
+from virtualenv.util.six import ensure_text
+
+
+class Wheel(object):
+    def __init__(self, path):
+        # https://www.python.org/dev/peps/pep-0427/#file-name-convention
+        # The wheel filename is {distribution}-{version}(-{build tag})?-{python tag}-{abi tag}-{platform tag}.whl
+        self.path = path
+        self._parts = path.stem.split("-")
+
+    @classmethod
+    def from_path(cls, path):
+        if path is not None and path.suffix == ".whl" and len(path.stem.split("-")) >= 5:
+            return cls(path)
+        return None
+
+    @property
+    def distribution(self):
+        return self._parts[0]
+
+    @property
+    def version(self):
+        return self._parts[1]
+
+    @property
+    def version_tuple(self):
+        return self.as_version_tuple(self.version)
+
+    @staticmethod
+    def as_version_tuple(version):
+        result = []
+        for part in version.split(".")[0:3]:
+            try:
+                result.append(int(part))
+            except ValueError:
+                break
+        if not result:
+            raise ValueError(version)
+        return tuple(result)
+
+    @property
+    def name(self):
+        return self.path.name
+
+    def support_py(self, py_version):
+        name = "{}.dist-info/METADATA".format("-".join(self.path.stem.split("-")[0:2]))
+        with ZipFile(ensure_text(str(self.path)), "r") as zip_file:
+            metadata = zip_file.read(name).decode("utf-8")
+        marker = "Requires-Python:"
+        requires = next((i[len(marker) :] for i in metadata.splitlines() if i.startswith(marker)), None)
+        if requires is None:  # if it does not specify a python requires the assumption is compatible
+            return True
+        py_version_int = tuple(int(i) for i in py_version.split("."))
+        for require in (i.strip() for i in requires.split(",")):
+            # https://www.python.org/dev/peps/pep-0345/#version-specifiers
+            for operator, check in [
+                ("!=", lambda v: py_version_int != v),
+                ("==", lambda v: py_version_int == v),
+                ("<=", lambda v: py_version_int <= v),
+                (">=", lambda v: py_version_int >= v),
+                ("<", lambda v: py_version_int < v),
+                (">", lambda v: py_version_int > v),
+            ]:
+                if require.startswith(operator):
+                    ver_str = require[len(operator) :].strip()
+                    version = tuple((int(i) if i != "*" else None) for i in ver_str.split("."))[0:2]
+                    if not check(version):
+                        return False
+                    break
+        return True
+
+    def __repr__(self):
+        return "{}({})".format(self.__class__.__name__, self.path)
+
+    def __str__(self):
+        return str(self.path)
+
+
+def discover_wheels(from_folder, distribution, version, for_py_version):
+    wheels = []
+    for filename in from_folder.iterdir():
+        wheel = Wheel.from_path(filename)
+        if wheel and wheel.distribution == distribution:
+            if version is None or wheel.version == version:
+                if wheel.support_py(for_py_version):
+                    wheels.append(wheel)
+    return sorted(wheels, key=attrgetter("version_tuple", "distribution"), reverse=True)
+
+
+class Version:
+    #: the version bundled with virtualenv
+    bundle = "bundle"
+    embed = "embed"
+    #: custom version handlers
+    non_version = (
+        bundle,
+        embed,
+    )
+
+    @staticmethod
+    def of_version(value):
+        return None if value in Version.non_version else value
+
+    @staticmethod
+    def as_pip_req(distribution, version):
+        return "{}{}".format(distribution, Version.as_version_spec(version))
+
+    @staticmethod
+    def as_version_spec(version):
+        of_version = Version.of_version(version)
+        return "" if of_version is None else "=={}".format(of_version)