From 864e2eee09522640b5e527f04b277d0e6978a42a Mon Sep 17 00:00:00 2001
From: Pradyun Gedam <3275593+pradyunsg@users.noreply.github.com>
Date: Sun, 2 Aug 2020 07:44:24 +0530
Subject: [PATCH] Merge pull request #8659 from
 uranusjr/fix-get-distribution-dot-in-name

Canonicalize name in check_if_exists
---
 news/8645.bugfix                         |  2 ++
 src/pip/_internal/req/req_install.py     | 28 +++++++-------------
 tests/functional/test_install_upgrade.py | 33 ++++++++++++++++++++++++
 3 files changed, 44 insertions(+), 19 deletions(-)
 create mode 100644 news/8645.bugfix

diff --git a/news/8645.bugfix b/news/8645.bugfix
new file mode 100644
index 00000000000..a388d24e4ad
--- /dev/null
+++ b/news/8645.bugfix
@@ -0,0 +1,2 @@
+Correctly find already-installed distributions with dot (``.``) in the name
+and uninstall them when needed.
diff --git a/src/pip/_internal/req/req_install.py b/src/pip/_internal/req/req_install.py
index 644930a1528..4759f4af6f0 100644
--- a/src/pip/_internal/req/req_install.py
+++ b/src/pip/_internal/req/req_install.py
@@ -429,25 +429,13 @@ def check_if_exists(self, use_user_site):
         """
         if self.req is None:
             return
-        # get_distribution() will resolve the entire list of requirements
-        # anyway, and we've already determined that we need the requirement
-        # in question, so strip the marker so that we don't try to
-        # evaluate it.
-        no_marker = Requirement(str(self.req))
-        no_marker.marker = None
-
-        # pkg_resources uses the canonical name to look up packages, but
-        # the name passed passed to get_distribution is not canonicalized
-        # so we have to explicitly convert it to a canonical name
-        no_marker.name = canonicalize_name(no_marker.name)
-        try:
-            self.satisfied_by = pkg_resources.get_distribution(str(no_marker))
-        except pkg_resources.DistributionNotFound:
+        existing_dist = get_distribution(self.req.name)
+        if not existing_dist:
             return
-        except pkg_resources.VersionConflict:
-            existing_dist = get_distribution(
-                self.req.name
-            )
+
+        existing_version = existing_dist.parsed_version
+        if not self.req.specifier.contains(existing_version, prereleases=True):
+            self.satisfied_by = None
             if use_user_site:
                 if dist_in_usersite(existing_dist):
                     self.should_reinstall = True
@@ -461,11 +449,13 @@ def check_if_exists(self, use_user_site):
             else:
                 self.should_reinstall = True
         else:
-            if self.editable and self.satisfied_by:
+            if self.editable:
                 self.should_reinstall = True
                 # when installing editables, nothing pre-existing should ever
                 # satisfy
                 self.satisfied_by = None
+            else:
+                self.satisfied_by = existing_dist
 
     # Things valid for wheels
     @property
diff --git a/tests/functional/test_install_upgrade.py b/tests/functional/test_install_upgrade.py
index e45bf31483e..02e221101c5 100644
--- a/tests/functional/test_install_upgrade.py
+++ b/tests/functional/test_install_upgrade.py
@@ -1,3 +1,4 @@
+import itertools
 import os
 import sys
 import textwrap
@@ -7,6 +8,7 @@
 from tests.lib import pyversion  # noqa: F401
 from tests.lib import assert_all_changes
 from tests.lib.local_repos import local_checkout
+from tests.lib.wheel import make_wheel
 
 
 @pytest.mark.network
@@ -439,3 +441,34 @@ def prep_ve(self, script, version, pip_src, distribute=False):
             cwd=pip_src,
             expect_stderr=True,
         )
+
+
+@pytest.mark.parametrize("req1, req2", list(itertools.product(
+    ["foo.bar", "foo_bar", "foo-bar"], ["foo.bar", "foo_bar", "foo-bar"],
+)))
+def test_install_find_existing_package_canonicalize(script, req1, req2):
+    """Ensure an already-installed dist is found no matter how the dist name
+    was normalized on installation. (pypa/pip#8645)
+    """
+    # Create and install a package that's not available in the later stage.
+    req_container = script.scratch_path.joinpath("foo-bar")
+    req_container.mkdir()
+    req_path = make_wheel("foo_bar", "1.0").save_to_dir(req_container)
+    script.pip("install", "--no-index", req_path)
+
+    # Depend on the previously installed, but now unavailable package.
+    pkg_container = script.scratch_path.joinpath("pkg")
+    pkg_container.mkdir()
+    make_wheel(
+        "pkg",
+        "1.0",
+        metadata_updates={"Requires-Dist": req2},
+    ).save_to_dir(pkg_container)
+
+    # Ensure the previously installed package can be correctly used to match
+    # the dependency.
+    result = script.pip(
+        "install", "--no-index", "--find-links", pkg_container, "pkg",
+    )
+    satisfied_message = "Requirement already satisfied: {}".format(req2)
+    assert satisfied_message in result.stdout, str(result)