New submission from Ilja Everilä:
When passing a class implementing the dunder __iter__ that raises to
csv.writer.writerows it hides the original exception and raises a TypeError
instead.
In the raised TypeError the __context__ and __cause__ both are None.
For example:
>>> class X:
... def __iter__(self):
... raise RuntimeError("I'm hidden")
...
>>> x = X()
>>> list(x)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "<stdin>", line 3, in __iter__
RuntimeError: I'm hidden
>>> import csv
>>> csv.writer(open('foo.csv', 'w', newline='')).writerows(x)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: writerows() argument must be iterable
>>> try:
... csv.writer(open('foo.csv', 'w', newline='')).writerows(x)
... except TypeError as e:
... e_ = e
>>> e_.__context__ is None
True
>>> e_.__cause__ is None
True
It would seem that for reasons unknown to me either PyObject_GetIter loses the
exception context or the call to PyErr_SetString in csv_writerows hides it.
----------
messages: 260673
nosy: Ilja Everilä
priority: normal
severity: normal
status: open
title: csv.writer.writerows masks exceptions from __iter__
type: behavior
_______________________________________
Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue26407>
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