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bpo-44110: Improve string's __getitem__ error message #26042

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Merged
serhiy-storchaka merged 3 commits into from
Jun 27, 2021
Merged

bpo-44110: Improve string's __getitem__ error message #26042

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af0f75b
Improve str error messages
miguendes May 8, 2021
0ccfa55
Improve tests
miguendes May 11, 2021
e78a9b9
Simplify test helper
miguendes May 12, 2021
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8 changes: 7 additions & 1 deletion Lib/test/string_tests.py
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Original file line number Diff line number Diff line change
Expand Up @@ -80,12 +80,14 @@ class subtype(self.__class__.type2test):
self.assertIsNot(obj, realresult)

# check that obj.method(*args) raises exc
def checkraises(self, exc, obj, methodname, *args):
def checkraises(self, exc, obj, methodname, *args, expected_msg=None):
obj = self.fixtype(obj)
args = self.fixtype(args)
with self.assertRaises(exc) as cm:
getattr(obj, methodname)(*args)
self.assertNotEqual(str(cm.exception), '')
if expected_msg is not None:
self.assertEqual(str(cm.exception), expected_msg)

# call obj.method(*args) without any checks
def checkcall(self, obj, methodname, *args):
Expand Down Expand Up @@ -1195,6 +1197,10 @@ def test_subscript(self):

self.checkraises(TypeError, 'abc', '__getitem__', 'def')

for idx_type in ('def', object()):
expected_msg = "string indices must be integers, not '{}'".format(type(idx_type).__name__)
self.checkraises(TypeError, 'abc', '__getitem__', idx_type, expected_msg=expected_msg)

def test_slice(self):
self.checkequal('abc', 'abc', '__getitem__', slice(0, 1000))
self.checkequal('abc', 'abc', '__getitem__', slice(0, 3))
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4 changes: 3 additions & 1 deletion Lib/test/test_userstring.py
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Expand Up @@ -27,12 +27,14 @@ def checkequal(self, result, object, methodname, *args, **kwargs):
realresult
)

def checkraises(self, exc, obj, methodname, *args):
def checkraises(self, exc, obj, methodname, *args, expected_msg=None):
obj = self.fixtype(obj)
# we don't fix the arguments, because UserString can't cope with it
with self.assertRaises(exc) as cm:
getattr(obj, methodname)(*args)
self.assertNotEqual(str(cm.exception), '')
if expected_msg is not None:
self.assertEqual(str(cm.exception), expected_msg)

def checkcall(self, object, methodname, *args):
object = self.fixtype(object)
Expand Down
1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Core and Builtins/2021-05-11-21-52-44.bpo-44110.VqbAsB.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
Improve :func:`str.__getitem__` error message
3 changes: 2 additions & 1 deletion Objects/unicodeobject.c
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Expand Up @@ -14564,7 +14564,8 @@ unicode_subscript(PyObject* self, PyObject* item)
assert(_PyUnicode_CheckConsistency(result, 1));
return result;
} else {
PyErr_SetString(PyExc_TypeError, "string indices must be integers");
PyErr_Format(PyExc_TypeError, "string indices must be integers, not '%.200s'",
Py_TYPE(item)->tp_name);
return NULL;
}
}
Expand Down