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bpo-45607: Make it possible to enrich exception displays via setting their __note__ field (GH-29880)

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Irit Katriel 2021-12-03 22:01:15 +00:00 committed by GitHub
parent d9301703fb
commit 5bb7ef2768
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10 changed files with 183 additions and 5 deletions
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8
Doc/library/exceptions.rst
View File

@ -127,6 +127,14 @@ The following exceptions are used mostly as base classes for other exceptions.
tb = sys.exc_info()[2]
raise OtherException(...).with_traceback(tb)
.. attribute:: __note__
A mutable field which is :const:`None` by default and can be set to a string.
If it is not :const:`None`, it is included in the traceback. This field can
be used to enrich exceptions after they have been caught.
.. versionadded:: 3.11
.. exception:: Exception

6
Doc/whatsnew/3.11.rst
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@ -146,6 +146,12 @@ The :option:`-X` ``no_debug_ranges`` option and the environment variable
See :pep:`657` for more details. (Contributed by Pablo Galindo, Batuhan Taskaya
and Ammar Askar in :issue:`43950`.)
Exceptions can be enriched with a string ``__note__``
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The ``__note__`` field was added to :exc:`BaseException`. It is ``None``
by default but can be set to a string which is added to the exception's
traceback. (Contributed by Irit Katriel in :issue:`45607`.)
Other Language Changes
======================

2
Include/cpython/pyerrors.h
View File

@ -6,7 +6,7 @@
/* PyException_HEAD defines the initial segment of every exception class. */
#define PyException_HEAD PyObject_HEAD PyObject *dict;\
PyObject *args; PyObject *traceback;\
PyObject *args; PyObject *note; PyObject *traceback;\
PyObject *context; PyObject *cause;\
char suppress_context;

21
Lib/test/test_exceptions.py
View File

@ -516,6 +516,27 @@ class ExceptionTests(unittest.TestCase):
'pickled "%r", attribute "%s' %
(e, checkArgName))
def test_note(self):
for e in [BaseException(1), Exception(2), ValueError(3)]:
with self.subTest(e=e):
self.assertIsNone(e.__note__)
e.__note__ = "My Note"
self.assertEqual(e.__note__, "My Note")
with self.assertRaises(TypeError):
e.__note__ = 42
self.assertEqual(e.__note__, "My Note")
e.__note__ = "Your Note"
self.assertEqual(e.__note__, "Your Note")
with self.assertRaises(TypeError):
del e.__note__
self.assertEqual(e.__note__, "Your Note")
e.__note__ = None
self.assertIsNone(e.__note__)
def testWithTraceback(self):
try:
raise IndexError(4)

8
Lib/test/test_sys.py
View File

@ -1298,13 +1298,13 @@ class SizeofTest(unittest.TestCase):
class C(object): pass
check(C.__dict__, size('P'))
# BaseException
check(BaseException(), size('5Pb'))
check(BaseException(), size('6Pb'))
# UnicodeEncodeError
check(UnicodeEncodeError("", "", 0, 0, ""), size('5Pb 2P2nP'))
check(UnicodeEncodeError("", "", 0, 0, ""), size('6Pb 2P2nP'))
# UnicodeDecodeError
check(UnicodeDecodeError("", b"", 0, 0, ""), size('5Pb 2P2nP'))
check(UnicodeDecodeError("", b"", 0, 0, ""), size('6Pb 2P2nP'))
# UnicodeTranslateError
check(UnicodeTranslateError("", 0, 1, ""), size('5Pb 2P2nP'))
check(UnicodeTranslateError("", 0, 1, ""), size('6Pb 2P2nP'))
# ellipses
check(Ellipsis, size(''))
# EncodingMap

69
Lib/test/test_traceback.py
View File

@ -1224,6 +1224,22 @@ class BaseExceptionReportingTests:
exp = "\n".join(expected)
self.assertEqual(exp, err)
def test_exception_with_note(self):
e = ValueError(42)
vanilla = self.get_report(e)
e.__note__ = 'My Note'
self.assertEqual(self.get_report(e), vanilla + 'My Note\n')
e.__note__ = ''
self.assertEqual(self.get_report(e), vanilla + '\n')
e.__note__ = 'Your Note'
self.assertEqual(self.get_report(e), vanilla + 'Your Note\n')
e.__note__ = None
self.assertEqual(self.get_report(e), vanilla)
def test_exception_qualname(self):
class A:
class B:
@ -1566,6 +1582,59 @@ class BaseExceptionReportingTests:
report = self.get_report(exc)
self.assertEqual(report, expected)
def test_exception_group_with_notes(self):
def exc():
try:
excs = []
for msg in ['bad value', 'terrible value']:
try:
raise ValueError(msg)
except ValueError as e:
e.__note__ = f'the {msg}'
excs.append(e)
raise ExceptionGroup("nested", excs)
except ExceptionGroup as e:
e.__note__ = ('>> Multi line note\n'
'>> Because I am such\n'
'>> an important exception.\n'
'>> empty lines work too\n'
'\n'
'(that was an empty line)')
raise
expected = (f' + Exception Group Traceback (most recent call last):\n'
f' | File "{__file__}", line {self.callable_line}, in get_exception\n'
f' | exception_or_callable()\n'
f' | ^^^^^^^^^^^^^^^^^^^^^^^\n'
f' | File "{__file__}", line {exc.__code__.co_firstlineno + 9}, in exc\n'
f' | raise ExceptionGroup("nested", excs)\n'
f' | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\n'
f' | ExceptionGroup: nested\n'
f' | >> Multi line note\n'
f' | >> Because I am such\n'
f' | >> an important exception.\n'
f' | >> empty lines work too\n'
f' | \n'
f' | (that was an empty line)\n'
f' +-+---------------- 1 ----------------\n'
f' | Traceback (most recent call last):\n'
f' | File "{__file__}", line {exc.__code__.co_firstlineno + 5}, in exc\n'
f' | raise ValueError(msg)\n'
f' | ^^^^^^^^^^^^^^^^^^^^^\n'
f' | ValueError: bad value\n'
f' | the bad value\n'
f' +---------------- 2 ----------------\n'
f' | Traceback (most recent call last):\n'
f' | File "{__file__}", line {exc.__code__.co_firstlineno + 5}, in exc\n'
f' | raise ValueError(msg)\n'
f' | ^^^^^^^^^^^^^^^^^^^^^\n'
f' | ValueError: terrible value\n'
f' | the terrible value\n'
f' +------------------------------------\n')
report = self.get_report(exc)
self.assertEqual(report, expected)
class PyExcReportingTests(BaseExceptionReportingTests, unittest.TestCase):
#

4
Lib/traceback.py
View File

@ -685,6 +685,8 @@ class TracebackException:
# Capture now to permit freeing resources: only complication is in the
# unofficial API _format_final_exc_line
self._str = _some_str(exc_value)
self.__note__ = exc_value.__note__ if exc_value else None
if exc_type and issubclass(exc_type, SyntaxError):
# Handle SyntaxError's specially
self.filename = exc_value.filename
@ -816,6 +818,8 @@ class TracebackException:
yield _format_final_exc_line(stype, self._str)
else:
yield from self._format_syntax_error(stype)
if self.__note__ is not None:
yield from [l + '\n' for l in self.__note__.split('\n')]
def _format_syntax_error(self, stype):
"""Format SyntaxError exceptions (internal helper)."""

4
Misc/NEWS.d/next/Core and Builtins/2021-12-01-15-38-04.bpo-45607.JhuF8b.rst Normal file
View File

@ -0,0 +1,4 @@
The ``__note__`` field was added to :exc:`BaseException`. It is ``None``
by default but can be set to a string which is added to the exception's
traceback.

31
Objects/exceptions.c
View File

@ -46,6 +46,7 @@ BaseException_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
return NULL;
/* the dict is created on the fly in PyObject_GenericSetAttr */
self->dict = NULL;
self->note = NULL;
self->traceback = self->cause = self->context = NULL;
self->suppress_context = 0;
@ -81,6 +82,7 @@ BaseException_clear(PyBaseExceptionObject *self)
{
Py_CLEAR(self->dict);
Py_CLEAR(self->args);
Py_CLEAR(self->note);
Py_CLEAR(self->traceback);
Py_CLEAR(self->cause);
Py_CLEAR(self->context);
@ -105,6 +107,7 @@ BaseException_traverse(PyBaseExceptionObject *self, visitproc visit, void *arg)
{
Py_VISIT(self->dict);
Py_VISIT(self->args);
Py_VISIT(self->note);
Py_VISIT(self->traceback);
Py_VISIT(self->cause);
Py_VISIT(self->context);
@ -216,6 +219,33 @@ BaseException_set_args(PyBaseExceptionObject *self, PyObject *val, void *Py_UNUS
return 0;
}
static PyObject *
BaseException_get_note(PyBaseExceptionObject *self, void *Py_UNUSED(ignored))
{
if (self->note == NULL) {
Py_RETURN_NONE;
}
return Py_NewRef(self->note);
}
static int
BaseException_set_note(PyBaseExceptionObject *self, PyObject *note,
void *Py_UNUSED(ignored))
{
if (note == NULL) {
PyErr_SetString(PyExc_TypeError, "__note__ may not be deleted");
return -1;
}
else if (note != Py_None && !PyUnicode_CheckExact(note)) {
PyErr_SetString(PyExc_TypeError, "__note__ must be a string or None");
return -1;
}
Py_INCREF(note);
Py_XSETREF(self->note, note);
return 0;
}
static PyObject *
BaseException_get_tb(PyBaseExceptionObject *self, void *Py_UNUSED(ignored))
{
@ -306,6 +336,7 @@ BaseException_set_cause(PyObject *self, PyObject *arg, void *Py_UNUSED(ignored))
static PyGetSetDef BaseException_getset[] = {
{"__dict__", PyObject_GenericGetDict, PyObject_GenericSetDict},
{"args", (getter)BaseException_get_args, (setter)BaseException_set_args},
{"__note__", (getter)BaseException_get_note, (setter)BaseException_set_note},
{"__traceback__", (getter)BaseException_get_tb, (setter)BaseException_set_tb},
{"__context__", BaseException_get_context,
BaseException_set_context, PyDoc_STR("exception context")},

35
Python/pythonrun.c
View File

@ -1083,6 +1083,41 @@ print_exception(struct exception_print_context *ctx, PyObject *value)
PyErr_Clear();
}
err += PyFile_WriteString("\n", f);
if (err == 0 && PyExceptionInstance_Check(value)) {
_Py_IDENTIFIER(__note__);
PyObject *note = _PyObject_GetAttrId(value, &PyId___note__);
if (note == NULL) {
err = -1;
}
if (err == 0 && PyUnicode_Check(note)) {
_Py_static_string(PyId_newline, "\n");
PyObject *lines = PyUnicode_Split(
note, _PyUnicode_FromId(&PyId_newline), -1);
if (lines == NULL) {
err = -1;
}
else {
Py_ssize_t n = PyList_GET_SIZE(lines);
for (Py_ssize_t i = 0; i < n; i++) {
if (err == 0) {
PyObject *line = PyList_GET_ITEM(lines, i);
assert(PyUnicode_Check(line));
err = write_indented_margin(ctx, f);
if (err == 0) {
err = PyFile_WriteObject(line, f, Py_PRINT_RAW);
}
if (err == 0) {
err = PyFile_WriteString("\n", f);
}
}
}
}
Py_DECREF(lines);
}
Py_XDECREF(note);
}
Py_XDECREF(tb);
Py_DECREF(value);
/* If an error happened here, don't show it.