Issue #27487: Warn if submodule already imported before runpy execution
Also try to clarify the find_spec() error message.
diff --git a/Lib/runpy.py b/Lib/runpy.py
index af6205d..e290c21 100644
--- a/Lib/runpy.py
+++ b/Lib/runpy.py
@@ -114,6 +114,15 @@
if e.name is None or (e.name != pkg_name and
not pkg_name.startswith(e.name + ".")):
raise
+ # Warn if the module has already been imported under its normal name
+ existing = sys.modules.get(mod_name)
+ if existing is not None and not hasattr(existing, "__path__"):
+ from warnings import warn
+ msg = "{mod_name!r} found in sys.modules after import of " \
+ "package {pkg_name!r}, but prior to execution of " \
+ "{mod_name!r}; this may result in unpredictable " \
+ "behaviour".format(mod_name=mod_name, pkg_name=pkg_name)
+ warn(RuntimeWarning(msg))
try:
spec = importlib.util.find_spec(mod_name)
@@ -121,7 +130,7 @@
# This hack fixes an impedance mismatch between pkgutil and
# importlib, where the latter raises other errors for cases where
# pkgutil previously raised ImportError
- msg = "Error while finding spec for {!r} ({}: {})"
+ msg = "Error while finding module specification for {!r} ({}: {})"
raise error(msg.format(mod_name, type(ex).__name__, ex)) from ex
if spec is None:
raise error("No module named %s" % mod_name)