Re-install local candidates unconditionally

Signed-off-by: Pradyun Gedam <[email protected]>

Author: pradyunsg

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

@@ -132,15 +132,19 @@ def resolve(self, root_reqs, check_supported_wheels):
 
             # Check if there is already an installation under the same name,
             # and set a flag for later stages to uninstall it, if needed.
-            # * There isn't, good -- no uninstalltion needed.
+            #
+            # * There is no existing installation. Nothing to uninstall.
+            # * The candidate is a local path/file. Always reinstall.
             # * The --force-reinstall flag is set. Always reinstall.
             # * The installation is different in version or editable-ness, so
             #   we need to uninstall it to install the new distribution.
             # * The installed version is the same as the pending distribution.
-            #   Skip this distrubiton altogether to save work.
+            #   Skip this distribution altogether to save work.
             installed_dist = self.factory.get_dist_to_uninstall(candidate)
             if installed_dist is None:
                 ireq.should_reinstall = False
+            elif candidate.source_link.is_file:
+                ireq.should_reinstall = True
             elif self.factory.force_reinstall:
                 ireq.should_reinstall = True
             elif installed_dist.parsed_version != candidate.version:

tests/functional/test_new_resolver.py

@@ -1132,3 +1132,43 @@ def test_new_resolver_check_wheel_version_normalized(
         "simple"
     )
     assert_installed(script, simple="0.1.0+local.1")
+
+
+def test_new_resolver_does_reinstall_local_wheels(script):
+    archive_path = create_basic_wheel_for_package(
+        script,
+        "pkg",
+        "1.0",
+    )
+    script.pip(
+        "install", "--no-cache-dir", "--no-index",
+        archive_path,
+    )
+    assert_installed(script, pkg="1.0")
+
+    result = script.pip(
+        "install", "--no-cache-dir", "--no-index",
+        archive_path,
+    )
+    assert "Installing collected packages: pkg" in result.stdout, str(result)
+    assert_installed(script, pkg="1.0")
+
+
+def test_new_resolver_does_reinstall_local_paths(script):
+    pkg = create_test_package_with_setup(
+        script,
+        name="pkg",
+        version="1.0"
+    )
+    script.pip(
+        "install", "--no-cache-dir", "--no-index",
+        pkg,
+    )
+    assert_installed(script, pkg="1.0")
+
+    result = script.pip(
+        "install", "--no-cache-dir", "--no-index",
+        pkg,
+    )
+    assert "Installing collected packages: pkg" in result.stdout, str(result)
+    assert_installed(script, pkg="1.0")