From 0c98f1923101e5905c54ba07650a043fca374f4b Mon Sep 17 00:00:00 2001
From: Ran Benita <ran@unusedvar.com>
Date: Sat, 8 Jan 2022 22:41:14 +0200
Subject: [PATCH] config: make confcutdir check a bit more clear & correct

I think this named function makes the code a bit easier to understand.

Also change the check to explicitly check for "is a sub-path of" instead
of the previous check which only worked assuming that path is within
confcutdir or a direct parent of it.
---
 src/_pytest/config/__init__.py | 25 ++++++++++++++++++-------
 src/_pytest/main.py            |  3 +--
 2 files changed, 19 insertions(+), 9 deletions(-)

diff --git a/src/_pytest/config/__init__.py b/src/_pytest/config/__init__.py
index 79b2ad598..a30ee6cee 100644
--- a/src/_pytest/config/__init__.py
+++ b/src/_pytest/config/__init__.py
@@ -521,6 +521,19 @@ class PytestPluginManager(PluginManager):
         if not foundanchor:
             self._try_load_conftest(current, namespace.importmode, rootpath)
 
+    def _is_in_confcutdir(self, path: Path) -> bool:
+        """Whether a path is within the confcutdir.
+
+        When false, should not load conftest.
+        """
+        if self._confcutdir is None:
+            return True
+        try:
+            path.relative_to(self._confcutdir)
+        except ValueError:
+            return False
+        return True
+
     def _try_load_conftest(
         self, anchor: Path, importmode: Union[str, ImportMode], rootpath: Path
     ) -> None:
@@ -552,14 +565,12 @@ class PytestPluginManager(PluginManager):
         # and allow users to opt into looking into the rootdir parent
         # directories instead of requiring to specify confcutdir.
         clist = []
-        confcutdir_parents = self._confcutdir.parents if self._confcutdir else []
         for parent in reversed((directory, *directory.parents)):
-            if parent in confcutdir_parents:
-                continue
-            conftestpath = parent / "conftest.py"
-            if conftestpath.is_file():
-                mod = self._importconftest(conftestpath, importmode, rootpath)
-                clist.append(mod)
+            if self._is_in_confcutdir(parent):
+                conftestpath = parent / "conftest.py"
+                if conftestpath.is_file():
+                    mod = self._importconftest(conftestpath, importmode, rootpath)
+                    clist.append(mod)
         self._dirpath2confmods[directory] = clist
         return clist
 
diff --git a/src/_pytest/main.py b/src/_pytest/main.py
index 952c70350..afe613fd0 100644
--- a/src/_pytest/main.py
+++ b/src/_pytest/main.py
@@ -689,9 +689,8 @@ class Session(nodes.FSCollector):
             # No point in finding packages when collecting doctests.
             if not self.config.getoption("doctestmodules", False):
                 pm = self.config.pluginmanager
-                confcutdir = pm._confcutdir
                 for parent in (argpath, *argpath.parents):
-                    if confcutdir and parent in confcutdir.parents:
+                    if not pm._is_in_confcutdir(argpath):
                         break
 
                     if parent.is_dir():