use .metadata distribution info when possible

news/11512.bugfix.rst

@@ -0,0 +1 @@
+Avoid downloading wheels when performing a ``--dry-run`` install when .metadata files are used.

src/pip/_internal/commands/install.py

@@ -398,7 +398,9 @@ def run(self, options: Values, args: List[str]) -> int:
             self.trace_basic_info(finder)
 
             requirement_set = resolver.resolve(
-                reqs, check_supported_wheels=not options.target_dir
+                reqs,
+                check_supported_wheels=not options.target_dir,
+                dry_run=options.dry_run,
             )
 
             if options.json_report_file:

src/pip/_internal/operations/prepare.py

@@ -400,6 +400,8 @@ def _fetch_metadata_using_link_data_attr(
             raise MetadataInconsistent(
                 req, "Name", req.req.name, metadata_dist.raw_name
             )
+        # (5) Store the dist in the install requirement for reporting
+        req.dist_from_metadata = metadata_dist
         return metadata_dist
 
     def _fetch_metadata_using_lazy_wheel(
@@ -490,6 +492,16 @@ def prepare_linked_requirement(
             # None of the optimizations worked, fully prepare the requirement
             return self._prepare_linked_requirement(req, parallel_builds)
 
+    def prepare_download_info(self, reqs: Iterable[InstallRequirement]) -> None:
+        """Prepare linked requirements with download_info, if needed."""
+        # During install --dry-run, .metadata files or lazy wheels may be used when determining
+        # distribution dependencies. The associated wheel does not need to be downloaded so the
+        # download_info need to be derived from the link. If the link does not contain a hash no
+        # hash will be included in the download_info.
+        for req in reqs:
+            if req.download_info is None:
+                req.download_info = direct_url_from_link(req.link, req.source_dir)
+
     def prepare_linked_requirements_more(
         self, reqs: Iterable[InstallRequirement], parallel_builds: bool = False
     ) -> None:

src/pip/_internal/req/req_install.py

@@ -185,6 +185,10 @@ def __init__(
         # This requirement needs more preparation before it can be built
         self.needs_more_preparation = False
 
+        # Distribution from the .metadata file referenced by the PEP 658
+        # data-dist-info-metadata attribute.
+        self.dist_from_metadata: Optional[BaseDistribution] = None
+
     def __str__(self) -> str:
         if self.req:
             s = str(self.req)
@@ -568,6 +572,8 @@ def get_dist(self) -> BaseDistribution:
             return get_wheel_distribution(
                 FilesystemWheel(self.local_file_path), canonicalize_name(self.name)
             )
+        elif self.is_wheel and self.dist_from_metadata:
+            return self.dist_from_metadata
         raise AssertionError(
             f"InstallRequirement {self} has no metadata directory and no wheel: "
             f"can't make a distribution."

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

@@ -68,7 +68,10 @@ def __init__(
         self._result: Optional[Result] = None
 
     def resolve(
-        self, root_reqs: List[InstallRequirement], check_supported_wheels: bool
+        self,
+        root_reqs: List[InstallRequirement],
+        check_supported_wheels: bool,
+        dry_run: bool = False,
     ) -> RequirementSet:
         collected = self.factory.collect_root_requirements(root_reqs)
         provider = PipProvider(
@@ -158,7 +161,10 @@ def resolve(
             req_set.add_named_requirement(ireq)
 
         reqs = req_set.all_requirements
-        self.factory.preparer.prepare_linked_requirements_more(reqs)
+        if dry_run:
+            self.factory.preparer.prepare_download_info(reqs)
+        else:
+            self.factory.preparer.prepare_linked_requirements_more(reqs)
         return req_set
 
     def get_installation_order(