[RFC] code location as a namedtuple

src/_pytest/compat.py

@@ -13,6 +13,7 @@ from pathlib import Path
 from typing import Any
 from typing import Callable
 from typing import Generic
+from typing import NamedTuple
 from typing import NoReturn
 from typing import TYPE_CHECKING
 from typing import TypeVar
@@ -94,17 +95,35 @@ def is_async_function(func: object) -> bool:
 
 
 def getlocation(function, curdir: str | None = None) -> str:
+class CodeLocation(NamedTuple):
+    path: Path
+    lineno: int
+
+
+def CodeLocation__str__(self: CodeLocation) -> str:
+    """Python 3.6 hack for NamedTuple __str__"""
+    return f"{self.path}:{self.lineno}"
+
+
+setattr(CodeLocation, "__str__", CodeLocation__str__)
+
+
+def getlocation(function, curdir: Path | None) -> CodeLocation:
     function = get_real_func(function)
     fn = Path(inspect.getfile(function))
     lineno = function.__code__.co_firstlineno
+
+    # TODO: this cycle indicates a larger issue
+    from .pathlib import bestrelpath
+
     if curdir is not None:
         try:
-            relfn = fn.relative_to(curdir)
+            relfn = Path(bestrelpath(curdir, fn))
         except ValueError:
             pass
         else:
-            return "%s:%d" % (relfn, lineno + 1)
+            return CodeLocation(relfn, lineno + 1)
-    return "%s:%d" % (fn, lineno + 1)
+    return CodeLocation(fn, lineno + 1)
 
 
 def num_mock_patch_args(function) -> int:

src/_pytest/fixtures.py

@@ -1210,7 +1210,7 @@ class FixtureFunctionMarker:
 
         name = self.name or function.__name__
         if name == "request":
-            location = getlocation(function)
+            location = getlocation(function, None)
             fail(
                 "'request' is a reserved word for fixtures, use another name:\n  {}".format(
                     location

src/_pytest/python.py

@@ -39,6 +39,7 @@ from _pytest._io import TerminalWriter
 from _pytest._io.saferepr import saferepr
 from _pytest.compat import ascii_escaped
 from _pytest.compat import assert_never
+from _pytest.compat import CodeLocation
 from _pytest.compat import final
 from _pytest.compat import get_default_arg_names
 from _pytest.compat import get_real_func
@@ -1634,14 +1635,14 @@ def _showfixtures_main(config: Config, session: Session) -> None:
     fm = session._fixturemanager
 
     available = []
-    seen: Set[Tuple[str, str]] = set()
+    seen: Set[Tuple[str, CodeLocation]] = set()
 
     for argname, fixturedefs in fm._arg2fixturedefs.items():
         assert fixturedefs is not None
         if not fixturedefs:
             continue
         for fixturedef in fixturedefs:
-            loc = getlocation(fixturedef.func, str(curdir))
+            loc = getlocation(fixturedef.func, curdir)
             if (fixturedef.argname, loc) in seen:
                 continue
             seen.add((fixturedef.argname, loc))