Clean up code style and internal interface

Co-Authored-By: Pradyun Gedam <pradyunsg@gmail.com>
Co-Authored-By: Chris Hunt <chrahunt@gmail.com>

src/pip/_internal/network/download.py

@@ -164,11 +164,14 @@ class Downloader(object):
             raise
 
         filename = _get_http_response_filename(resp, link)
+        filepath = os.path.join(location, filename)
+
         chunks = _prepare_download(resp, link, self._progress_bar)
-        with open(os.path.join(location, filename), 'wb') as content_file:
+        with open(filepath, 'wb') as content_file:
             for chunk in chunks:
                 content_file.write(chunk)
-            return content_file.name, resp.headers.get('Content-Type', '')
+        content_type = resp.headers.get('Content-Type', '')
+        return filepath, content_type
 
     def download_many(self, links, location):
         # type: (Iterable[Link], str) -> Iterable[Tuple[str, Tuple[str, str]]]

src/pip/_internal/operations/prepare.py

@@ -45,7 +45,7 @@ from pip._internal.utils.unpacking import unpack_file
 from pip._internal.vcs import vcs
 
 if MYPY_CHECK_RUNNING:
-    from typing import Callable, Dict, List, Optional, Tuple
+    from typing import Callable, Dict, Iterable, List, Optional, Tuple
 
     from mypy_extensions import TypedDict
     from pip._vendor.pkg_resources import Distribution
@@ -484,8 +484,10 @@ class RequirementPreparer(object):
         return self._prepare_linked_requirement(req, parallel_builds)
 
     def prepare_linked_requirements_more(self, reqs, parallel_builds=False):
-        # type: (List[InstallRequirement], bool) -> None
+        # type: (Iterable[InstallRequirement], bool) -> None
         """Prepare a linked requirement more, if needed."""
+        reqs = [req for req in reqs if req.needs_more_preparation]
+
         # Let's download to a temporary directory.
         tmpdir = TempDirectory(kind="unpack", globally_managed=True).path
         links = (req.link for req in reqs)
@@ -505,9 +507,7 @@ class RequirementPreparer(object):
 
         with indent_log():
             self._ensure_link_req_src_dir(req, download_dir, parallel_builds)
-            if link.url in self._downloaded:
-                local_file = File(*self._downloaded[link.url])
-            else:
+            if link.url not in self._downloaded:
                 try:
                     local_file = unpack_url(
                         link, req.source_dir, self.downloader, download_dir,
@@ -518,6 +518,8 @@ class RequirementPreparer(object):
                         'Could not install requirement {} because of HTTP '
                         'error {} for URL {}'.format(req, exc, link)
                     )
+            else:
+                local_file = File(*self._downloaded[link.url])
 
             # For use in later processing, preserve the file path on the
             # requirement.

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

@@ -160,11 +160,8 @@ class Resolver(BaseResolver):
 
             req_set.add_named_requirement(ireq)
 
-        self.factory.preparer.prepare_linked_requirements_more([
-            req for req in req_set.all_requirements
-            if req.needs_more_preparation
-        ])
-
+        reqs = req_set.all_requirements
+        self.factory.preparer.prepare_linked_requirements_more(reqs)
         return req_set
 
     def get_installation_order(self, req_set):