module __file__ attribute is not the canonical path

src/_pytest/_py/path.py

@@ -1128,6 +1128,7 @@ def pyimport(self, modname=None, ensuresyspath=True):
                 # be in a namespace package ... too icky to check
             modfile = mod.__file__
             assert modfile is not None
+            modfile = os.path.realpath(modfile)
             if modfile[-4:] in (".pyc", ".pyo"):
                 modfile = modfile[:-1]
             elif modfile.endswith("$py.class"):

src/_pytest/config/__init__.py

@@ -58,6 +58,7 @@
 from _pytest.pathlib import bestrelpath
 from _pytest.pathlib import import_path
 from _pytest.pathlib import ImportMode
+from _pytest.pathlib import module_realfile
 from _pytest.pathlib import resolve_package_path
 from _pytest.pathlib import safe_exists
 from _pytest.stash import Stash
@@ -631,8 +632,7 @@ def _rget_with_confmod(
     def _importconftest(
         self, conftestpath: Path, importmode: Union[str, ImportMode], rootpath: Path
     ) -> types.ModuleType:
-        conftestpath_plugin_name = str(conftestpath)
-        existing = self.get_plugin(conftestpath_plugin_name)
+        existing = self.get_plugin(str(conftestpath))
         if existing is not None:
             return cast(types.ModuleType, existing)
 
@@ -668,7 +668,7 @@ def _importconftest(
                         )
                     mods.append(mod)
         self.trace(f"loading conftestmodule {mod!r}")
-        self.consider_conftest(mod, registration_name=conftestpath_plugin_name)
+        self.consider_conftest(mod)
         return mod
 
     def _check_non_top_pytest_plugins(
@@ -748,11 +748,9 @@ def consider_pluginarg(self, arg: str) -> None:
                     del self._name2plugin["pytest_" + name]
             self.import_plugin(arg, consider_entry_points=True)
 
-    def consider_conftest(
-        self, conftestmodule: types.ModuleType, registration_name: str
-    ) -> None:
+    def consider_conftest(self, conftestmodule: types.ModuleType) -> None:
         """:meta private:"""
-        self.register(conftestmodule, name=registration_name)
+        self.register(conftestmodule, name=module_realfile(conftestmodule))
 
     def consider_env(self) -> None:
         """:meta private:"""

src/_pytest/fixtures.py

@@ -62,6 +62,7 @@
 from _pytest.outcomes import TEST_OUTCOME
 from _pytest.pathlib import absolutepath
 from _pytest.pathlib import bestrelpath
+from _pytest.pathlib import module_realfile
 from _pytest.scope import _ScopeName
 from _pytest.scope import HIGH_SCOPES
 from _pytest.scope import Scope
@@ -1486,16 +1487,20 @@ def getfixtureinfo(
     def pytest_plugin_registered(self, plugin: _PluggyPlugin) -> None:
         nodeid = None
         try:
-            p = absolutepath(plugin.__file__)  # type: ignore[attr-defined]
+            module_file = module_realfile(plugin)  # type: ignore[arg-type]
         except AttributeError:
-            pass
-        else:
-            # Construct the base nodeid which is later used to check
-            # what fixtures are visible for particular tests (as denoted
-            # by their test id).
-            if p.name == "conftest.py":
+            module_file = None
+
+        # Construct the base nodeid which is later used to check
+        # what fixtures are visible for particular tests (as denoted
+        # by their test id).
+        if module_file is not None:
+            module_purefile = Path(module_file)
+            if module_purefile.name == "conftest.py":
                 try:
-                    nodeid = str(p.parent.relative_to(self.config.rootpath))
+                    nodeid = str(
+                        module_purefile.parent.relative_to(self.config.rootpath)
+                    )
                 except ValueError:
                     nodeid = ""
                 if nodeid == ".":

src/_pytest/helpconfig.py

@@ -12,6 +12,7 @@
 from _pytest.config import ExitCode
 from _pytest.config import PrintHelp
 from _pytest.config.argparsing import Parser
+from _pytest.pathlib import module_realfile
 from _pytest.terminal import TerminalReporter
 
 
@@ -265,7 +266,7 @@ def pytest_report_header(config: Config) -> List[str]:
         items = config.pluginmanager.list_name_plugin()
         for name, plugin in items:
             if hasattr(plugin, "__file__"):
-                r = plugin.__file__
+                r = module_realfile(plugin)
             else:
                 r = repr(plugin)
             lines.append(f"    {name:<20}: {r}")

src/_pytest/pathlib.py

@@ -572,7 +572,7 @@ def import_path(
 
     ignore = os.environ.get("PY_IGNORE_IMPORTMISMATCH", "")
     if ignore != "1":
-        module_file = mod.__file__
+        module_file = module_realfile(mod)
         if module_file is None:
             raise ImportPathMismatchError(module_name, module_file, path)
 
@@ -788,3 +788,14 @@ def safe_exists(p: Path) -> bool:
         # ValueError: stat: path too long for Windows
         # OSError: [WinError 123] The filename, directory name, or volume label syntax is incorrect
         return False
+
+
+def module_realfile(module: ModuleType) -> Optional[str]:
+    """Return the canonical __file__ of the module without resolving symlinks."""
+    filename = module.__file__
+    if filename is None:
+        return None
+    resolved_filename = os.path.realpath(filename)
+    if resolved_filename.lower() == filename.lower():
+        return resolved_filename
+    return filename

testing/test_pathlib.py

@@ -24,6 +24,7 @@
 from _pytest.pathlib import insert_missing_modules
 from _pytest.pathlib import maybe_delete_a_numbered_dir
 from _pytest.pathlib import module_name_from_path
+from _pytest.pathlib import module_realfile
 from _pytest.pathlib import resolve_package_path
 from _pytest.pathlib import safe_exists
 from _pytest.pathlib import symlink_or_skip
@@ -712,3 +713,36 @@ def test_safe_exists(tmp_path: Path) -> None:
         side_effect=ValueError("name too long"),
     ):
         assert safe_exists(p) is False
+
+
+@pytest.mark.skipif(
+    not sys.platform.startswith("win"),
+    reason="requires a case-insensitive file system",
+)
+def test_module_realfile(tmp_path: Path) -> None:
+    dirname_with_caps = tmp_path / "Testdir"
+    dirname_with_caps.mkdir()
+    filename = dirname_with_caps / "_test_safe_exists.py"
+    linkname = dirname_with_caps / "_test_safe_exists_link.py"
+    linkname.symlink_to(filename)
+
+    mod = ModuleType("dummy.name")
+
+    mod.__file__ = None
+    assert module_realfile(mod) is None
+
+    # Test path resolving
+
+    mod.__file__ = str(filename)
+    assert module_realfile(mod) == str(filename)
+
+    mod.__file__ = str(filename).lower()
+    assert module_realfile(mod) == str(filename)
+
+    # Test symlink preservation
+
+    mod.__file__ = str(linkname)
+    assert module_realfile(mod) == mod.__file__
+
+    mod.__file__ = str(linkname).lower()
+    assert module_realfile(mod) == mod.__file__

testing/test_pluginmanager.py

@@ -118,17 +118,14 @@ def test_conftestpath_case_sensitivity(self, pytester: Pytester) -> None:
         plugin = config.pluginmanager.get_plugin(str(conftest))
         assert plugin is mod
 
-        mod_uppercase = config.pluginmanager._importconftest(
-            conftest_upper_case,
-            importmode="prepend",
-            rootpath=pytester.path,
-        )
+        with pytest.raises(ValueError, match="Plugin name already registered"):
+            config.pluginmanager._importconftest(
+                conftest_upper_case,
+                importmode="prepend",
+                rootpath=pytester.path,
+            )
         plugin_uppercase = config.pluginmanager.get_plugin(str(conftest_upper_case))
-        assert plugin_uppercase is mod_uppercase
-
-        # No str(conftestpath) normalization so conftest should be imported
-        # twice and modules should be different objects
-        assert mod is not mod_uppercase
+        assert plugin_uppercase is None
 
     def test_hook_tracing(self, _config_for_test: Config) -> None:
         pytestpm = _config_for_test.pluginmanager  # fully initialized with plugins
@@ -400,7 +397,7 @@ def test_consider_conftest_deps(
             pytester.makepyfile("pytest_plugins='xyz'"), root=pytester.path
         )
         with pytest.raises(ImportError):
-            pytestpm.consider_conftest(mod, registration_name="unused")
+            pytestpm.consider_conftest(mod)
 
 
 class TestPytestPluginManagerBootstrapming: