1 files changed, 67 insertions, 19 deletions
diff --git a/Lib/importlib/resources/_common.py b/Lib/importlib/resources/_common.py
index 92a37e2c12b..a3902535342 100644
--- a/Lib/importlib/resources/_common.py
+++ b/Lib/importlib/resources/_common.py
@@ -5,25 +5,58 @@ import functools
 import contextlib
 import types
 import importlib
+import inspect
+import warnings
+import itertools
 
-from typing import Union, Optional
+from typing import Union, Optional, cast
 from .abc import ResourceReader, Traversable
 
 from ._adapters import wrap_spec
 
 Package = Union[types.ModuleType, str]
+Anchor = Package
 
 
-def files(package):
-    # type: (Package) -> Traversable
+def package_to_anchor(func):
     """
-    Get a Traversable resource from a package
+    Replace 'package' parameter as 'anchor' and warn about the change.
+
+    Other errors should fall through.
+
+    >>> files('a', 'b')
+    Traceback (most recent call last):
+    TypeError: files() takes from 0 to 1 positional arguments but 2 were given
+    """
+    undefined = object()
+
+    @functools.wraps(func)
+    def wrapper(anchor=undefined, package=undefined):
+        if package is not undefined:
+            if anchor is not undefined:
+                return func(anchor, package)
+            warnings.warn(
+                "First parameter to files is renamed to 'anchor'",
+                DeprecationWarning,
+                stacklevel=2,
+            )
+            return func(package)
+        elif anchor is undefined:
+            return func()
+        return func(anchor)
+
+    return wrapper
+
+
+@package_to_anchor
+def files(anchor: Optional[Anchor] = None) -> Traversable:
+    """
+    Get a Traversable resource for an anchor.
     """
-    return from_package(get_package(package))
+    return from_package(resolve(anchor))
 
 
-def get_resource_reader(package):
-    # type: (types.ModuleType) -> Optional[ResourceReader]
+def get_resource_reader(package: types.ModuleType) -> Optional[ResourceReader]:
     """
     Return the package's loader if it's a ResourceReader.
     """
@@ -39,24 +72,39 @@ def get_resource_reader(package):
     return reader(spec.name)  # type: ignore
 
 
-def resolve(cand):
-    # type: (Package) -> types.ModuleType
-    return cand if isinstance(cand, types.ModuleType) else importlib.import_module(cand)
+@functools.singledispatch
+def resolve(cand: Optional[Anchor]) -> types.ModuleType:
+    return cast(types.ModuleType, cand)
+
+
+@resolve.register
+def _(cand: str) -> types.ModuleType:
+    return importlib.import_module(cand)
+
 
+@resolve.register
+def _(cand: None) -> types.ModuleType:
+    return resolve(_infer_caller().f_globals['__name__'])
 
-def get_package(package):
-    # type: (Package) -> types.ModuleType
-    """Take a package name or module object and return the module.
 
-    Raise an exception if the resolved module is not a package.
+def _infer_caller():
     """
-    resolved = resolve(package)
-    if wrap_spec(resolved).submodule_search_locations is None:
-        raise TypeError(f'{package!r} is not a package')
-    return resolved
+    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):
+def from_package(package: types.ModuleType):
     """
     Return a Traversable object for the given package.