add --unstable-feature=shallow_wheels!

news/8448.feature

@@ -1 +1 @@
-Add a set of utilities in ``pip._internal.network.shallow`` for fetching metadata from remote wheel files without downloading the entire file. Link these utilities into the v2 resolver by adding a new ShallowWheelDistribution AbstractDistribution subclass. Expose this behavior via a --shallow-wheels command-line option to ``pip download``. This produces a marked performance improvement.
+Add a set of utilities in ``pip._internal.network.shallow`` for fetching metadata from remote wheel files without downloading the entire file. Link these utilities into the v2 resolver by adding a new ShallowWheelDistribution AbstractDistribution subclass. Expose this behavior via a --unstable-feature=shallow_wheels command-line option to ``pip download``. This produces a marked performance improvement.

src/pip/_internal/cli/cmdoptions.py

@@ -919,7 +919,7 @@ def check_list_path_option(options):
     metavar='feature',
     action='append',
     default=[],
-    choices=['resolver'],
+    choices=['resolver', 'shallow_wheels'],
     help=SUPPRESS_HELP,  # TODO: Enable this when the resolver actually works.
     # help='Enable unstable feature(s) that may be backward incompatible.',
 )  # type: Callable[..., Option]

src/pip/_internal/cli/req_command.py

@@ -231,7 +231,7 @@ def make_requirement_preparer(
             finder=finder,
             require_hashes=options.require_hashes,
             use_user_site=use_user_site,
-            use_shallow_wheels=True,
+            use_shallow_wheels=('shallow_wheels' in options.unstable_features),
         )
 
     @staticmethod

src/pip/_internal/commands/install.py

@@ -326,6 +326,7 @@ def run(self, options, args):
             requirement_set = resolver.resolve(
                 reqs, check_supported_wheels=not options.target_dir
             )
+            requirement_set.perform_all_final_hydration()
 
             try:
                 pip_req = requirement_set.get_requirement("pip")

src/pip/_internal/commands/wheel.py

@@ -155,6 +155,7 @@ def run(self, options, args):
         requirement_set = resolver.resolve(
             reqs, check_supported_wheels=True
         )
+        requirement_set.perform_all_final_hydration()
 
         reqs_to_build = [
             r for r in requirement_set.requirements.values()

src/pip/_internal/resolution/resolvelib/resolver.py

@@ -9,7 +9,7 @@
 from pip._internal.distributions.shallow_wheel import (
     DistributionNeedingFinalHydration,
 )
-from pip._internal.exceptions import DistributionNotFound, InstallationError
+from pip._internal.exceptions import InstallationError
 from pip._internal.req.req_set import RequirementSet
 from pip._internal.resolution.base import BaseResolver
 from pip._internal.resolution.resolvelib.provider import PipProvider