Move caller inference to its own function. Removes hard-coded distance to caller by finding the first caller not in this file. Avoids expensive use of inspect when package is specified.

Author: jaraco

importlib_resources/_common.py

@@ -6,23 +6,22 @@
 import types
 import importlib
 import inspect
+import itertools
 
-from typing import Union, Optional, cast, Dict
+from typing import Union, Optional, cast
 from .abc import ResourceReader, Traversable
 
 from ._compat import wrap_spec
 
 Package = Union[types.ModuleType, str]
 Anchor = Union[Package, None]
-ModuleContext = Dict[str, str]
 
 
 def files(package: Anchor = None) -> Traversable:
     """
     Get a Traversable resource for an anchor.
     """
-    context = inspect.stack()[1].frame.f_globals  # type: ignore
-    return from_package(resolve(package, context))
+    return from_package(resolve(package))
 
 
 def get_resource_reader(package: types.ModuleType) -> Optional[ResourceReader]:
@@ -42,18 +41,35 @@ def get_resource_reader(package: types.ModuleType) -> Optional[ResourceReader]:
 
 
 @functools.singledispatch
-def resolve(cand: Anchor, context) -> types.ModuleType:
+def resolve(cand: Anchor) -> types.ModuleType:
     return cast(types.ModuleType, cand)
 
 
 @resolve.register
-def _(cand: str, context) -> types.ModuleType:
+def _(cand: str) -> types.ModuleType:
     return importlib.import_module(cand)
 
 
 @resolve.register
-def _(cand: None, context: ModuleContext) -> types.ModuleType:
-    return resolve(context['__name__'], context)
+def _(cand: None) -> types.ModuleType:
+    return resolve(_infer_caller().f_globals['__name__'])
+
+
+def _infer_caller():
+    """
+    Walk the stack and find the frame of the first caller not in this module.
+    """
+
+    def is_this_file(frame_info):
+        return frame_info.filename == __file__
+
+    def is_wrapper(frame_info):
+        return frame_info.function == 'wrapper'
+
+    not_this_file = itertools.filterfalse(is_this_file, inspect.stack())
+    # also exclude 'wrapper' due to singledispatch in the call stack
+    callers = itertools.filterfalse(is_wrapper, not_this_file)
+    return next(callers).frame
 
 
 def from_package(package: types.ModuleType):