bpo-42856: Add --with-wheel-pkg-dir=PATH configure option (GH-24210)

Add --with-wheel-pkg-dir=PATH option to the ./configure script. If
specified, the ensurepip module looks for setuptools and pip wheel
packages in this directory: if both are present, these wheel packages
are used instead of ensurepip bundled wheel packages.

Some Linux distribution packaging policies recommend against bundling
dependencies. For example, Fedora installs wheel packages in the
/usr/share/python-wheels/ directory and don't install the
ensurepip._bundled package.

ensurepip: Remove unused runpy import.

8 files changed, 220 insertions, 36 deletions

diff --git a/Doc/library/ensurepip.rst b/Doc/library/ensurepip.rst
index a522125..fa1b42c 100644
--- a/Doc/library/ensurepip.rst
+++ b/Doc/library/ensurepip.rst
@@ -48,7 +48,7 @@ The simplest possible invocation is::
 
 This invocation will install ``pip`` if it is not already installed,
 but otherwise does nothing. To ensure the installed version of ``pip``
-is at least as recent as the one bundled with ``ensurepip``, pass the
+is at least as recent as the one available in ``ensurepip``, pass the
 ``--upgrade`` option::
 
     python -m ensurepip --upgrade
@@ -86,7 +86,7 @@ Module API
 
 .. function:: version()
 
-   Returns a string specifying the bundled version of pip that will be
+   Returns a string specifying the available version of pip that will be
    installed when bootstrapping an environment.
 
 .. function:: bootstrap(root=None, upgrade=False, user=False, \
@@ -100,7 +100,7 @@ Module API
    for the current environment.
 
    *upgrade* indicates whether or not to upgrade an existing installation
-   of an earlier version of ``pip`` to the bundled version.
+   of an earlier version of ``pip`` to the available version.
 
    *user* indicates whether to use the user scheme rather than installing
    globally.
diff --git a/Doc/whatsnew/3.10.rst b/Doc/whatsnew/3.10.rst
index 7edc552..7fe2b96 100644
--- a/Doc/whatsnew/3.10.rst
+++ b/Doc/whatsnew/3.10.rst
@@ -621,6 +621,18 @@ Build Changes
   don't build nor install test modules.
   (Contributed by Xavier de Gaye, Thomas Petazzoni and Peixing Xin in :issue:`27640`.)
 
+* Add ``--with-wheel-pkg-dir=PATH`` option to the ``./configure`` script. If
+  specified, the :mod:`ensurepip` module looks for ``setuptools`` and ``pip``
+  wheel packages in this directory: if both are present, these wheel packages
+  are used instead of ensurepip bundled wheel packages.
+
+  Some Linux distribution packaging policies recommend against bundling
+  dependencies. For example, Fedora installs wheel packages in the
+  ``/usr/share/python-wheels/`` directory and don't install the
+  ``ensurepip._bundled`` package.
+
+  (Contributed by Victor Stinner in :issue:`42856`.)
+
 
 C API Changes
 =============
diff --git a/Lib/ensurepip/__init__.py b/Lib/ensurepip/__init__.py
index cb2882e..2276fd7 100644
--- a/Lib/ensurepip/__init__.py
+++ b/Lib/ensurepip/__init__.py
@@ -1,27 +1,82 @@
+import collections
 import os
 import os.path
+import subprocess
 import sys
-import runpy
+import sysconfig
 import tempfile
-import subprocess
 from importlib import resources
 
-from . import _bundled
-
 
 
 __all__ = ["version", "bootstrap"]
-
-
+_PACKAGE_NAMES = ('setuptools', 'pip')
 _SETUPTOOLS_VERSION = "47.1.0"
-
 _PIP_VERSION = "20.2.3"
-
 _PROJECTS = [
     ("setuptools", _SETUPTOOLS_VERSION, "py3"),
     ("pip", _PIP_VERSION, "py2.py3"),
 ]
 
+# Packages bundled in ensurepip._bundled have wheel_name set.
+# Packages from WHEEL_PKG_DIR have wheel_path set.
+_Package = collections.namedtuple('Package',
+                                  ('version', 'wheel_name', 'wheel_path'))
+
+# Directory of system wheel packages. Some Linux distribution packaging
+# policies recommend against bundling dependencies. For example, Fedora
+# installs wheel packages in the /usr/share/python-wheels/ directory and don't
+# install the ensurepip._bundled package.
+_WHEEL_PKG_DIR = sysconfig.get_config_var('WHEEL_PKG_DIR')
+
+
+def _find_packages(path):
+    packages = {}
+    try:
+        filenames = os.listdir(path)
+    except OSError:
+        # Ignore: path doesn't exist or permission error
+        filenames = ()
+    # Make the code deterministic if a directory contains multiple wheel files
+    # of the same package, but don't attempt to implement correct version
+    # comparison since this case should not happen.
+    filenames = sorted(filenames)
+    for filename in filenames:
+        # filename is like 'pip-20.2.3-py2.py3-none-any.whl'
+        if not filename.endswith(".whl"):
+            continue
+        for name in _PACKAGE_NAMES:
+            prefix = name + '-'
+            if filename.startswith(prefix):
+                break
+        else:
+            continue
+
+        # Extract '20.2.2' from 'pip-20.2.2-py2.py3-none-any.whl'
+        version = filename.removeprefix(prefix).partition('-')[0]
+        wheel_path = os.path.join(path, filename)
+        packages[name] = _Package(version, None, wheel_path)
+    return packages
+
+
+def _get_packages():
+    global _PACKAGES, _WHEEL_PKG_DIR
+    if _PACKAGES is not None:
+        return _PACKAGES
+
+    packages = {}
+    for name, version, py_tag in _PROJECTS:
+        wheel_name = f"{name}-{version}-{py_tag}-none-any.whl"
+        packages[name] = _Package(version, wheel_name, None)
+    if _WHEEL_PKG_DIR:
+        dir_packages = _find_packages(_WHEEL_PKG_DIR)
+        # only used the wheel package directory if all packages are found there
+        if all(name in dir_packages for name in _PACKAGE_NAMES):
+            packages = dir_packages
+    _PACKAGES = packages
+    return packages
+_PACKAGES = None
+
 
 def _run_pip(args, additional_paths=None):
     # Run the bootstraping in a subprocess to avoid leaking any state that happens
@@ -42,7 +97,8 @@ def version():
     """
     Returns a string specifying the bundled version of pip.
     """
-    return _PIP_VERSION
+    return _get_packages()['pip'].version
+
 
 def _disable_pip_configuration_settings():
     # We deliberately ignore all pip environment variables
@@ -104,16 +160,23 @@ def _bootstrap(*, root=None, upgrade=False, user=False,
         # Put our bundled wheels into a temporary directory and construct the
         # additional paths that need added to sys.path
         additional_paths = []
-        for project, version, py_tag in _PROJECTS:
-            wheel_name = "{}-{}-{}-none-any.whl".format(project, version, py_tag)
-            whl = resources.read_binary(
-                _bundled,
-                wheel_name,
-            )
-            with open(os.path.join(tmpdir, wheel_name), "wb") as fp:
+        for name, package in _get_packages().items():
+            if package.wheel_name:
+                # Use bundled wheel package
+                from ensurepip import _bundled
+                wheel_name = package.wheel_name
+                whl = resources.read_binary(_bundled, wheel_name)
+            else:
+                # Use the wheel package directory
+                with open(package.wheel_path, "rb") as fp:
+                    whl = fp.read()
+                wheel_name = os.path.basename(package.wheel_path)
+
+            filename = os.path.join(tmpdir, wheel_name)
+            with open(filename, "wb") as fp:
                 fp.write(whl)
 
-            additional_paths.append(os.path.join(tmpdir, wheel_name))
+            additional_paths.append(filename)
 
         # Construct the arguments to be passed to the pip command
         args = ["install", "--no-cache-dir", "--no-index", "--find-links", tmpdir]
@@ -126,7 +189,7 @@ def _bootstrap(*, root=None, upgrade=False, user=False,
         if verbosity:
             args += ["-" + "v" * verbosity]
 
-        return _run_pip(args + [p[0] for p in _PROJECTS], additional_paths)
+        return _run_pip([*args, *_PACKAGE_NAMES], additional_paths)
 
 def _uninstall_helper(*, verbosity=0):
     """Helper to support a clean default uninstall process on Windows
@@ -139,11 +202,14 @@ def _uninstall_helper(*, verbosity=0):
     except ImportError:
         return
 
-    # If the pip version doesn't match the bundled one, leave it alone
-    if pip.__version__ != _PIP_VERSION:
-        msg = ("ensurepip will only uninstall a matching version "
-               "({!r} installed, {!r} bundled)")
-        print(msg.format(pip.__version__, _PIP_VERSION), file=sys.stderr)
+    # If the installed pip version doesn't match the available one,
+    # leave it alone
+    available_version = version()
+    if pip.__version__ != available_version:
+        print(f"ensurepip will only uninstall a matching version "
+              f"({pip.__version__!r} installed, "
+              f"{available_version!r} available)",
+              file=sys.stderr)
         return
 
     _disable_pip_configuration_settings()
@@ -153,7 +219,7 @@ def _uninstall_helper(*, verbosity=0):
     if verbosity:
         args += ["-" + "v" * verbosity]
 
-    return _run_pip(args + [p[0] for p in reversed(_PROJECTS)])
+    return _run_pip([*args, *reversed(_PACKAGE_NAMES)])
 
 
 def _main(argv=None):
diff --git a/Lib/test/test_ensurepip.py b/Lib/test/test_ensurepip.py
index 4786d28..bfca0cd 100644
--- a/Lib/test/test_ensurepip.py
+++ b/Lib/test/test_ensurepip.py
@@ -1,19 +1,68 @@
-import unittest
-import unittest.mock
-import test.support
+import contextlib
 import os
 import os.path
-import contextlib
 import sys
+import tempfile
+import test.support
+import unittest
+import unittest.mock
 
 import ensurepip
 import ensurepip._uninstall
 
 
-class TestEnsurePipVersion(unittest.TestCase):
+class TestPackages(unittest.TestCase):
+    def touch(self, directory, filename):
+        fullname = os.path.join(directory, filename)
+        open(fullname, "wb").close()
+
+    def test_version(self):
+        # Test version()
+        with tempfile.TemporaryDirectory() as tmpdir:
+            self.touch(tmpdir, "pip-1.2.3b1-py2.py3-none-any.whl")
+            self.touch(tmpdir, "setuptools-49.1.3-py3-none-any.whl")
+            with (unittest.mock.patch.object(ensurepip, '_PACKAGES', None),
+                  unittest.mock.patch.object(ensurepip, '_WHEEL_PKG_DIR', tmpdir)):
+                self.assertEqual(ensurepip.version(), '1.2.3b1')
+
+    def test_get_packages_no_dir(self):
+        # Test _get_packages() without a wheel package directory
+        with (unittest.mock.patch.object(ensurepip, '_PACKAGES', None),
+              unittest.mock.patch.object(ensurepip, '_WHEEL_PKG_DIR', None)):
+            packages = ensurepip._get_packages()
+
+            # when bundled wheel packages are used, we get _PIP_VERSION
+            self.assertEqual(ensurepip._PIP_VERSION, ensurepip.version())
+
+        # use bundled wheel packages
+        self.assertIsNotNone(packages['pip'].wheel_name)
+        self.assertIsNotNone(packages['setuptools'].wheel_name)
+
+    def test_get_packages_with_dir(self):
+        # Test _get_packages() with a wheel package directory
+        setuptools_filename = "setuptools-49.1.3-py3-none-any.whl"
+        pip_filename = "pip-20.2.2-py2.py3-none-any.whl"
+
+        with tempfile.TemporaryDirectory() as tmpdir:
+            self.touch(tmpdir, setuptools_filename)
+            self.touch(tmpdir, pip_filename)
+            # not used, make sure that it's ignored
+            self.touch(tmpdir, "wheel-0.34.2-py2.py3-none-any.whl")
+
+            with (unittest.mock.patch.object(ensurepip, '_PACKAGES', None),
+                  unittest.mock.patch.object(ensurepip, '_WHEEL_PKG_DIR', tmpdir)):
+                packages = ensurepip._get_packages()
+
+            self.assertEqual(packages['setuptools'].version, '49.1.3')
+            self.assertEqual(packages['setuptools'].wheel_path,
+                             os.path.join(tmpdir, setuptools_filename))
+            self.assertEqual(packages['pip'].version, '20.2.2')
+            self.assertEqual(packages['pip'].wheel_path,
+                             os.path.join(tmpdir, pip_filename))
+
+            # wheel package is ignored
+            self.assertEqual(sorted(packages), ['pip', 'setuptools'])
 
-    def test_returns_version(self):
-        self.assertEqual(ensurepip._PIP_VERSION, ensurepip.version())
 
 class EnsurepipMixin:
 
@@ -27,6 +76,8 @@ class EnsurepipMixin:
         real_devnull = os.devnull
         os_patch = unittest.mock.patch("ensurepip.os")
         patched_os = os_patch.start()
+        # But expose os.listdir() used by _find_packages()
+        patched_os.listdir = os.listdir
         self.addCleanup(os_patch.stop)
         patched_os.devnull = real_devnull
         patched_os.path = os.path
@@ -147,7 +198,7 @@ class TestBootstrap(EnsurepipMixin, unittest.TestCase):
         self.assertEqual(self.os_environ["PIP_CONFIG_FILE"], os.devnull)
 
 @contextlib.contextmanager
-def fake_pip(version=ensurepip._PIP_VERSION):
+def fake_pip(version=ensurepip.version()):
     if version is None:
         pip = None
     else:
@@ -243,7 +294,7 @@ class TestUninstall(EnsurepipMixin, unittest.TestCase):
 
 # Basic testing of the main functions and their argument parsing
 
-EXPECTED_VERSION_OUTPUT = "pip " + ensurepip._PIP_VERSION
+EXPECTED_VERSION_OUTPUT = "pip " + ensurepip.version()
 
 class TestBootstrappingMainFunction(EnsurepipMixin, unittest.TestCase):
 
diff --git a/Makefile.pre.in b/Makefile.pre.in
index fa0b9d8..ca6b518 100644
--- a/Makefile.pre.in
+++ b/Makefile.pre.in
@@ -146,6 +146,8 @@ CONFINCLUDEDIR=	$(exec_prefix)/include
 PLATLIBDIR=	@PLATLIBDIR@
 SCRIPTDIR=	$(prefix)/$(PLATLIBDIR)
 ABIFLAGS=	@ABIFLAGS@
+# Variable used by ensurepip
+WHEEL_PKG_DIR=	@WHEEL_PKG_DIR@
 
 # Detailed destination directories
 BINLIBDEST=	@BINLIBDEST@
diff --git a/Misc/NEWS.d/next/Build/2021-01-07-12-51-38.bpo-42856.n3cMHV.rst b/Misc/NEWS.d/next/Build/2021-01-07-12-51-38.bpo-42856.n3cMHV.rst
new file mode 100644
index 0000000..6aab7a6
--- /dev/null
+++ b/Misc/NEWS.d/next/Build/2021-01-07-12-51-38.bpo-42856.n3cMHV.rst
@@ -0,0 +1,9 @@
+Add ``--with-wheel-pkg-dir=PATH`` option to the ``./configure`` script. If
+specified, the :mod:`ensurepip` module looks for ``setuptools`` and ``pip``
+wheel packages in this directory: if both are present, these wheel packages are
+used instead of ensurepip bundled wheel packages.
+
+Some Linux distribution packaging policies recommend against bundling
+dependencies. For example, Fedora installs wheel packages in the
+``/usr/share/python-wheels/`` directory and don't install the
+``ensurepip._bundled`` package.
diff --git a/configure b/configure
index 1d81c00..37ee369 100755
--- a/configure
+++ b/configure
@@ -630,6 +630,7 @@ OPENSSL_INCLUDES
 ENSUREPIP
 SRCDIRS
 THREADHEADERS
+WHEEL_PKG_DIR
 LIBPL
 PY_ENABLE_SHARED
 PLATLIBDIR
@@ -847,6 +848,7 @@ with_libm
 with_libc
 enable_big_digits
 with_platlibdir
+with_wheel_pkg_dir
 with_computed_gotos
 with_ensurepip
 with_openssl
@@ -1576,6 +1578,9 @@ Optional Packages:
                           system-dependent)
   --with-platlibdir=DIRNAME
                           Python library directory name (default is "lib")
+  --with-wheel-pkg-dir=PATH
+                          Directory of wheel packages used by ensurepip
+                          (default: none)
   --with-computed-gotos   enable computed gotos in evaluation loop (enabled by
                           default on supported compilers)
   --with-ensurepip[=install|upgrade|no]
@@ -15493,6 +15498,29 @@ else
 fi
 
 
+# Check for --with-wheel-pkg-dir=PATH
+
+WHEEL_PKG_DIR=""
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for --with-wheel-pkg-dir" >&5
+$as_echo_n "checking for --with-wheel-pkg-dir... " >&6; }
+
+# Check whether --with-wheel-pkg-dir was given.
+if test "${with_wheel_pkg_dir+set}" = set; then :
+  withval=$with_wheel_pkg_dir;
+if test -n "$withval"; then
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
+$as_echo "yes" >&6; }
+  WHEEL_PKG_DIR="$withval"
+else
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+fi
+else
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+fi
+
+
 # Check whether right shifting a negative integer extends the sign bit
 # or fills with zeros (like the Cray J90, according to Tim Peters).
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether right shift extends the sign bit" >&5
diff --git a/configure.ac b/configure.ac
index 08c462a..99077e9 100644
--- a/configure.ac
+++ b/configure.ac
@@ -4838,6 +4838,22 @@ else
 fi
 AC_SUBST(LIBPL)
 
+# Check for --with-wheel-pkg-dir=PATH
+AC_SUBST(WHEEL_PKG_DIR)
+WHEEL_PKG_DIR=""
+AC_MSG_CHECKING(for --with-wheel-pkg-dir)
+AC_ARG_WITH(wheel-pkg-dir,
+            AS_HELP_STRING([--with-wheel-pkg-dir=PATH],
+            [Directory of wheel packages used by ensurepip (default: none)]),
+[
+if test -n "$withval"; then
+  AC_MSG_RESULT(yes)
+  WHEEL_PKG_DIR="$withval"
+else
+  AC_MSG_RESULT(no)
+fi],
+[AC_MSG_RESULT(no)])
+
 # Check whether right shifting a negative integer extends the sign bit
 # or fills with zeros (like the Cray J90, according to Tim Peters).
 AC_MSG_CHECKING(whether right shift extends the sign bit)