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gh-128398: improve error messages when incorrectly using with and async with (#132218)

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Improve the error message with a suggestion when an object supporting the synchronous
(resp. asynchronous) context manager protocol is entered using `async with` (resp. `with`)
instead of `with` (resp. `async with`).
This commit is contained in:
Bénédikt Tran 2025-04-19 10:44:01 +02:00 • committed by GitHub
parent 95800fe6e7
commit 8a9c6c4d16
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GPG key ID: B5690EEEBB952194
10 changed files with 211 additions and 47 deletions
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74
Python/ceval.c
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@ -545,23 +545,51 @@ const conversion_func _PyEval_ConversionFuncs[4] = {
const _Py_SpecialMethod _Py_SpecialMethods[] = {
[SPECIAL___ENTER__] = {
.name = &_Py_ID(__enter__),
.error = "'%.200s' object does not support the "
"context manager protocol (missed __enter__ method)",
.error = (
"'%T' object does not support the context manager protocol "
"(missed __enter__ method)"
),
.error_suggestion = (
"'%T' object does not support the context manager protocol "
"(missed __enter__ method) but it supports the asynchronous "
"context manager protocol. Did you mean to use 'async with'?"
)
},
[SPECIAL___EXIT__] = {
.name = &_Py_ID(__exit__),
.error = "'%.200s' object does not support the "
"context manager protocol (missed __exit__ method)",
.error = (
"'%T' object does not support the context manager protocol "
"(missed __exit__ method)"
),
.error_suggestion = (
"'%T' object does not support the context manager protocol "
"(missed __exit__ method) but it supports the asynchronous "
"context manager protocol. Did you mean to use 'async with'?"
)
},
[SPECIAL___AENTER__] = {
.name = &_Py_ID(__aenter__),
.error = "'%.200s' object does not support the asynchronous "
"context manager protocol (missed __aenter__ method)",
.error = (
"'%T' object does not support the asynchronous "
"context manager protocol (missed __aenter__ method)"
),
.error_suggestion = (
"'%T' object does not support the asynchronous context manager "
"protocol (missed __aenter__ method) but it supports the context "
"manager protocol. Did you mean to use 'with'?"
)
},
[SPECIAL___AEXIT__] = {
.name = &_Py_ID(__aexit__),
.error = "'%.200s' object does not support the asynchronous "
"context manager protocol (missed __aexit__ method)",
.error = (
"'%T' object does not support the asynchronous "
"context manager protocol (missed __aexit__ method)"
),
.error_suggestion = (
"'%T' object does not support the asynchronous context manager "
"protocol (missed __aexit__ method) but it supports the context "
"manager protocol. Did you mean to use 'with'?"
)
}
};
@ -3380,3 +3408,33 @@ _PyEval_LoadName(PyThreadState *tstate, _PyInterpreterFrame *frame, PyObject *na
}
return value;
}
/* Check if a 'cls' provides the given special method. */
static inline int
type_has_special_method(PyTypeObject *cls, PyObject *name)
{
// _PyType_Lookup() does not set an exception and returns a borrowed ref
assert(!PyErr_Occurred());
PyObject *r = _PyType_Lookup(cls, name);
return r != NULL && Py_TYPE(r)->tp_descr_get != NULL;
}
int
_PyEval_SpecialMethodCanSuggest(PyObject *self, int oparg)
{
PyTypeObject *type = Py_TYPE(self);
switch (oparg) {
case SPECIAL___ENTER__:
case SPECIAL___EXIT__: {
return type_has_special_method(type, &_Py_ID(__aenter__))
&& type_has_special_method(type, &_Py_ID(__aexit__));
}
case SPECIAL___AENTER__:
case SPECIAL___AEXIT__: {
return type_has_special_method(type, &_Py_ID(__enter__))
&& type_has_special_method(type, &_Py_ID(__exit__));
}
default:
Py_FatalError("unsupported special method");
}
}