Introduce ireq.cached_wheel_source_link

src/pip/_internal/operations/prepare.py

@@ -575,10 +575,7 @@ def _prepare_linked_requirement(
                     "don't match, ignoring cached built wheel "
                     "and re-downloading source."
                 )
-                # For some reason req.original_link is not set here, even though
-                # req.is_wheel_from_cache is True. So we get the original
-                # link from download_info.
-                req.link = Link(req.download_info.url)  # TODO comes_from?
+                req.link = req.cached_wheel_source_link
                 link = req.link
 
         self._ensure_link_req_src_dir(req, parallel_builds)

src/pip/_internal/req/req_install.py

@@ -112,6 +112,9 @@ def __init__(
         # When is_wheel_from_cache is True, it means that this InstallRequirement
         # is a local wheel file in the cache of locally built wheels.
         self.is_wheel_from_cache = False
+        # When is_wheel_from_cache is True, this is the source link corresponding
+        # to the cache entry, which was used to download and build the cached wheel.
+        self.cached_wheel_source_link: Optional[Link] = None
 
         # Information about the location of the artifact that was downloaded . This
         # property is guaranteed to be set in resolver results.

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

@@ -431,6 +431,7 @@ def _populate_link(self, req: InstallRequirement) -> None:
         if cache_entry is not None:
             logger.debug("Using cached wheel link: %s", cache_entry.link)
             if req.link is req.original_link and cache_entry.persistent:
+                req.cached_wheel_source_link = req.link
                 req.is_wheel_from_cache = True
             if cache_entry.origin is not None:
                 req.download_info = cache_entry.origin

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

@@ -277,6 +277,7 @@ def __init__(
             assert ireq.link.is_wheel
             assert ireq.link.is_file
             if cache_entry.persistent and template.link is template.original_link:
+                ireq.cached_wheel_source_link = source_link
                 ireq.is_wheel_from_cache = True
             if cache_entry.origin is not None:
                 ireq.download_info = cache_entry.origin

tests/unit/test_req.py

@@ -412,6 +412,7 @@ def test_download_info_archive_legacy_cache(
             assert len(reqset.all_requirements) == 1
             req = reqset.all_requirements[0]
             assert req.is_wheel_from_cache
+            assert req.cached_wheel_source_link
             assert req.download_info
             assert req.download_info.url == url
             assert isinstance(req.download_info.info, ArchiveInfo)
@@ -438,6 +439,7 @@ def test_download_info_archive_cache_with_origin(
             assert len(reqset.all_requirements) == 1
             req = reqset.all_requirements[0]
             assert req.is_wheel_from_cache
+            assert req.cached_wheel_source_link
             assert req.download_info
             assert req.download_info.url == url
             assert isinstance(req.download_info.info, ArchiveInfo)