Better workaround for cache poisoning #3025

Make sure ``pip wheel`` never outputs pure python wheels with a
python implementation tag. Better fix/workaround for
`#3025 <https://github.com/pypa/pip/issues/3025>`_ by
using a per-implementation wheel cache instead of caching pure python
wheels with an implementation tag in their name.

Fixes #7296

news/7296.bugfix

@@ -0,0 +1,5 @@
+Make sure ``pip wheel`` never outputs pure python wheels with a
+python implementation tag. Better fix/workaround for
+`#3025 <https://github.com/pypa/pip/issues/3025>`_ by
+using a per-implementation wheel cache instead of caching pure python
+wheels with an implementation tag in their name.

src/pip/_internal/cache.py

@@ -12,6 +12,7 @@
 from pip._vendor.packaging.utils import canonicalize_name
 
 from pip._internal.models.link import Link
+from pip._internal.pep425tags import implementation_tag
 from pip._internal.utils.compat import expanduser
 from pip._internal.utils.temp_dir import TempDirectory
 from pip._internal.utils.typing import MYPY_CHECK_RUNNING
@@ -157,7 +158,9 @@ def get_path_for_link(self, link):
         parts = self._get_cache_path_parts(link)
 
         # Store wheels within the root cache_dir
-        return os.path.join(self.cache_dir, "wheels", *parts)
+        return os.path.join(
+            self.cache_dir, implementation_tag, "wheels", *parts
+        )
 
     def get(
         self,

src/pip/_internal/wheel_builder.py

@@ -9,7 +9,6 @@
 import re
 import shutil
 
-from pip._internal import pep425tags
 from pip._internal.models.link import Link
 from pip._internal.utils.logging import indent_log
 from pip._internal.utils.marker_files import has_delete_marker_file
@@ -433,10 +432,6 @@ def build(
             ', '.join([req.name for (req, _) in buildset]),
         )
 
-        python_tag = None
-        if should_unpack:
-            python_tag = pep425tags.implementation_tag
-
         with indent_log():
             build_success, build_failure = [], []
             for req, output_dir in buildset:
@@ -450,10 +445,7 @@ def build(
                     build_failure.append(req)
                     continue
 
-                wheel_file = self._build_one(
-                    req, output_dir,
-                    python_tag=python_tag,
-                )
+                wheel_file = self._build_one(req, output_dir)
                 if wheel_file:
                     if should_unpack:
                         # XXX: This is mildly duplicative with prepare_files,

tests/functional/test_install.py

@@ -1232,7 +1232,9 @@ def test_install_builds_wheels(script, data, with_wheel):
         'from pip._internal.utils import appdirs; '
         'print(appdirs.user_cache_dir("pip"))'
     ))
-    wheels_cache = os.path.join(res.stdout.rstrip('\n'), 'wheels')
+    wheels_cache = os.path.join(
+        res.stdout.rstrip('\n'), pep425tags.implementation_tag, 'wheels'
+    )
     # NB This incidentally tests a local tree + tarball inputs
     # see test_install_editable_from_git_autobuild_wheel for editable
     # vcs coverage.
@@ -1261,9 +1263,9 @@ def test_install_builds_wheels(script, data, with_wheel):
     assert "Running setup.py install for requir" not in str(res), str(res)
     # wheelbroken has to run install
     assert "Running setup.py install for wheelb" in str(res), str(res)
-    # We want to make sure we used the correct implementation tag
+    # We want to make sure pure python wheels do not have an implementation tag
     assert wheels == [
-        "Upper-2.0-{}-none-any.whl".format(pep425tags.implementation_tag),
+        "Upper-2.0-py{}-none-any.whl".format(sys.version_info[0]),
     ]