Issue pypa#2563: Read cached wheels from ~/.cache/pip/wheels

This won't put wheels into that directory, but will read them if they
are there. --no-cache-dir will disable reading such wheels.

docs/reference/pip_install.rst

@@ -319,6 +319,14 @@ Windows
   :file:`<CSIDL_LOCAL_APPDATA>\pip\Cache`
 
 
+Wheel cache
+***********
+
+Pip will read from the subdirectory ``wheels`` within the pip cache dir and use
+any packages found there. This is disabled via the same ``no-cache-dir`` option
+that disables the HTTP cache.
+
+
 Hash Verification
 +++++++++++++++++
 

pip/commands/install.py

@@ -200,6 +200,7 @@ def _build_package_finder(self, options, index_urls, session):
             allow_all_prereleases=options.pre,
             process_dependency_links=options.process_dependency_links,
             session=session,
+            wheel_cache=options.cache_dir and options.use_wheel,
         )
 
     def run(self, options, args):

pip/commands/list.py

@@ -87,6 +87,7 @@ def _build_package_finder(self, options, index_urls, session):
             trusted_hosts=options.trusted_hosts,
             process_dependency_links=options.process_dependency_links,
             session=session,
+            wheel_cache=options.cache_dir,
         )
 
     def run(self, options, args):

pip/commands/wheel.py

@@ -170,6 +170,7 @@ def run(self, options, args):
                 trusted_hosts=options.trusted_hosts,
                 process_dependency_links=options.process_dependency_links,
                 session=session,
+                wheel_cache=options.cache_dir,
             )
 
             build_delete = (not (options.no_clean or options.build_dir))

pip/index.py

@@ -1,6 +1,7 @@
 """Routines related to PyPI, indexes"""
 from __future__ import absolute_import
 
+from itertools import chain
 import logging
 import cgi
 import sys
@@ -24,6 +25,7 @@
 )
 from pip.download import url_to_path, path_to_url
 from pip.models import PyPI
+from pip.locations import WHEEL_CACHE_URL
 from pip.wheel import Wheel, wheel_ext
 from pip.pep425tags import supported_tags, supported_tags_noarch, get_platform
 from pip.req.req_requirement import InstallationCandidate
@@ -60,7 +62,12 @@ def __init__(self, find_links, index_urls,
                  use_wheel=True, allow_external=(), allow_unverified=(),
                  allow_all_external=False, allow_all_prereleases=False,
                  trusted_hosts=None, process_dependency_links=False,
-                 session=None):
+                 session=None, wheel_cache=True):
+        """Create a PackageFinder.
+
+        :param wheel_cache: If True (the default) the path for pip wheel
+            caching is added to the find_links setting.
+        """
         if session is None:
             raise TypeError(
                 "PackageFinder() missing 1 required keyword argument: "
@@ -73,7 +80,11 @@ def __init__(self, find_links, index_urls,
         # This is deliberately conservative - it might be fine just to
         # blindly normalize anything starting with a ~...
         self.find_links = []
-        for link in find_links:
+        if wheel_cache:
+            links = chain(find_links, [WHEEL_CACHE_URL()])
+        else:
+            links = find_links
+        for link in links:
             if link.startswith('~'):
                 new_link = normalize_path(link)
                 if os.path.exists(new_link):

pip/locations.py

@@ -11,6 +11,7 @@
 from distutils import sysconfig
 from distutils.command.install import install, SCHEME_KEYS
 
+import pip
 from pip.compat import get_path_uid, WINDOWS
 from pip.utils import appdirs
 from pip import exceptions
@@ -54,6 +55,10 @@
 
 # Application Directories
 USER_CACHE_DIR = appdirs.user_cache_dir("pip")
+# Not a constant because HOME is mangled during tests.
+WHEEL_CACHE_DIR = \
+    lambda: os.path.join(appdirs.user_cache_dir("pip"), 'wheels')
+WHEEL_CACHE_URL = lambda: pip.download.path_to_url(WHEEL_CACHE_DIR())
 
 
 DELETE_MARKER_MESSAGE = '''\

tests/unit/test_finder.py

@@ -6,6 +6,7 @@
 from pkg_resources import parse_version, Distribution
 from pip.req import InstallRequirement
 from pip.index import PackageFinder, Link
+from pip.locations import WHEEL_CACHE_URL
 from pip.exceptions import (
     BestVersionAlreadyInstalled, DistributionNotFound, InstallationError,
 )
@@ -768,3 +769,15 @@ def test_find_all_versions_find_links_and_index(data):
     versions = finder._find_all_versions('simple')
     # first the find-links versions then the page versions
     assert [str(v.version) for v in versions] == ['3.0', '2.0', '1.0', '1.0']
+
+
+def test_find_links_defaults_include_wheel_cache(data):
+    finder = PackageFinder(
+        [data.find_links], [], session=PipSession())
+    assert WHEEL_CACHE_URL() == finder.find_links[-1]
+
+
+def test_find_links_suppress_wheel_cache(data):
+    finder = PackageFinder(
+        [data.find_links], [], session=PipSession(), wheel_cache=False)
+    assert [data.find_links] == finder.find_links