Refactor in preparation for issue #1139 fix. (#4644)

Author: cjerdonek

news/FEE41119-80BF-49CB-B395-E71791996869.trivial

@@ -14,7 +14,7 @@
     DirectoryUrlHashUnsupported, HashUnpinned, InstallationError,
     PreviousBuildDirError, VcsHashUnsupported
 )
-from pip.utils import display_path, dist_in_usersite, normalize_path
+from pip.utils import display_path, normalize_path
 from pip.utils.hashes import MissingHashes
 from pip.utils.logging import indent_log
 from pip.vcs import vcs
@@ -164,8 +164,7 @@ def prepare_requirement(self, req, resolver):
         # satisfied_by is only evaluated by calling _check_skip_installed,
         # so it must be None here.
         assert req.satisfied_by is None
-        if not resolver.ignore_installed:
-            skip_reason = resolver._check_skip_installed(req)
+        skip_reason = resolver._check_skip_installed(req)
 
         if req.satisfied_by:
             return self._prepare_installed_requirement(
@@ -302,12 +301,7 @@ def _prepare_linked_requirement(self, req, resolver):
                     resolver.ignore_installed
                 )
                 if should_modify:
-                    # don't uninstall conflict if user install and
-                    # conflict is not user install
-                    if not (resolver.use_user_site and
-                            not dist_in_usersite(req.satisfied_by)):
-                        req.conflicts_with = req.satisfied_by
-                    req.satisfied_by = None
+                    resolver._set_req_to_reinstall(req)
                 else:
                     logger.info(
                         'Requirement already satisfied (use '

pip/operations/prepare.py

@@ -114,6 +114,16 @@ def _is_upgrade_allowed(self, req):
             assert self.upgrade_strategy == "only-if-needed"
             return req.is_direct
 
+    def _set_req_to_reinstall(self, req):
+        """
+        Set a requirement to be installed.
+        """
+        # Don't uninstall the conflict if doing a user install and the
+        # conflict is not a user install.
+        if not self.use_user_site or dist_in_usersite(req.satisfied_by):
+            req.conflicts_with = req.satisfied_by
+        req.satisfied_by = None
+
     # XXX: Stop passing requirement_set for options
     def _check_skip_installed(self, req_to_install):
         """Check if req_to_install should be skipped.
@@ -133,55 +143,36 @@ def _check_skip_installed(self, req_to_install):
 
         :return: A text reason for why it was skipped, or None.
         """
-        # Check whether to upgrade/reinstall this req or not.
-        req_to_install.check_if_exists()
-        if req_to_install.satisfied_by:
-            upgrade_allowed = self._is_upgrade_allowed(req_to_install)
-
-            # Is the best version is installed.
-            best_installed = False
-
-            if upgrade_allowed:
-                # For link based requirements we have to pull the
-                # tree down and inspect to assess the version #, so
-                # its handled way down.
-                should_check_possibility_for_upgrade = not (
-                    self.force_reinstall or req_to_install.link
-                )
-                if should_check_possibility_for_upgrade:
-                    try:
-                        self.finder.find_requirement(
-                            req_to_install, upgrade_allowed)
-                    except BestVersionAlreadyInstalled:
-                        best_installed = True
-                    except DistributionNotFound:
-                        # No distribution found, so we squash the
-                        # error - it will be raised later when we
-                        # re-try later to do the install.
-                        # Why don't we just raise here?
-                        pass
-
-                if not best_installed:
-                    # don't uninstall conflict if user install and
-                    # conflict is not user install
-                    if not (self.use_user_site and not
-                            dist_in_usersite(req_to_install.satisfied_by)):
-                        req_to_install.conflicts_with = \
-                            req_to_install.satisfied_by
-                    req_to_install.satisfied_by = None
-
-            # Figure out a nice message to say why we're skipping this.
-            if best_installed:
-                skip_reason = 'already up-to-date'
-            elif self.upgrade_strategy == "only-if-needed":
-                skip_reason = 'not upgraded as not directly required'
-            else:
-                skip_reason = 'already satisfied'
+        if self.ignore_installed:
+            return None
 
-            return skip_reason
-        else:
+        req_to_install.check_if_exists()
+        if not req_to_install.satisfied_by:
             return None
 
+        if not self._is_upgrade_allowed(req_to_install):
+            if self.upgrade_strategy == "only-if-needed":
+                return 'not upgraded as not directly required'
+            return 'already satisfied'
+
+        # Check for the possibility of an upgrade.  For link-based
+        # requirements we have to pull the tree down and inspect to assess
+        # the version #, so it's handled way down.
+        if not (self.force_reinstall or req_to_install.link):
+            try:
+                self.finder.find_requirement(req_to_install, upgrade=True)
+            except BestVersionAlreadyInstalled:
+                # Then the best version is installed.
+                return 'already up-to-date'
+            except DistributionNotFound:
+                # No distribution found, so we squash the error.  It will
+                # be raised later when we re-try later to do the install.
+                # Why don't we just raise here?
+                pass
+
+        self._set_req_to_reinstall(req_to_install)
+        return None
+
     def _resolve_one(self, requirement_set, req_to_install):
         """Prepare a single requirements file.