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bpo-20490: Improve circular import error message (GH-15308)

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This commit is contained in:
Anthony Sottile 2019-09-09 08:17:50 -07:00 committed by Steve Dower
parent 88b24f96ae
commit 65366bc8bd
5 changed files with 27 additions and 4 deletions
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10
Lib/test/test_import/__init__.py
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@ -1324,6 +1324,16 @@ def test_crossreference2(self):
self.assertIn('partially initialized module', errmsg)
self.assertIn('circular import', errmsg)
def test_circular_from_import(self):
with self.assertRaises(ImportError) as cm:
import test.test_import.data.circular_imports.from_cycle1
self.assertIn(
"cannot import name 'b' from partially initialized module "
"'test.test_import.data.circular_imports.from_cycle1' "
"(most likely due to a circular import)",
str(cm.exception),
)
if __name__ == '__main__':
# Test needs to be a package, so we can do relative imports.

2
Lib/test/test_import/data/circular_imports/from_cycle1.py Normal file
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@ -0,0 +1,2 @@
from .from_cycle2 import a
b = 1

2
Lib/test/test_import/data/circular_imports/from_cycle2.py Normal file
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@ -0,0 +1,2 @@
from .from_cycle1 import b
a = 1

2
Misc/NEWS.d/next/Core and Builtins/2019-08-15-12-48-36.bpo-20490.-hXeEn.rst Normal file
View file

@ -0,0 +1,2 @@
Improve import error message for partially initialized module on circular
``from`` imports - by Anthony Sottile.

15
Python/ceval.c
View file

@ -5233,10 +5233,17 @@ import_from(PyThreadState *tstate, PyObject *v, PyObject *name)
PyErr_SetImportError(errmsg, pkgname, NULL);
}
else {
errmsg = PyUnicode_FromFormat(
"cannot import name %R from %R (%S)",
name, pkgname_or_unknown, pkgpath
);
_Py_IDENTIFIER(__spec__);
PyObject *spec = _PyObject_GetAttrId(v, &PyId___spec__);
Py_XINCREF(spec);
const char *fmt =
_PyModuleSpec_IsInitializing(spec) ?
"cannot import name %R from partially initialized module %R "
"(most likely due to a circular import) (%S)" :
"cannot import name %R from %R (%S)";
Py_XDECREF(spec);
errmsg = PyUnicode_FromFormat(fmt, name, pkgname_or_unknown, pkgpath);
/* NULL checks for errmsg and pkgname done by PyErr_SetImportError. */
PyErr_SetImportError(errmsg, pkgname, pkgpath);
}