I'm trying to write some code that fixes a misconfigured sys.stdin on a case by case bases but unfortunately I cannot use TextIOWrapper for this because it always closes the underlying file:


Python

>>> import io
>>> sys.stdin.encoding
'ANSI_X3.4-1968'
>>> stdin = sys.stdin
>>> correct_stdin = io.TextIOWrapper(stdin.buffer, 'utf-8')
>>> correct_stdin.readline()
foobar
'foobar\n'
>>> del correct_stdin
>>> stdin.readline()
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: I/O operation on closed file.

Ideally there would be a way to disable this behavior.

It works if you detach the buffer beforehand:

    >>> import io, sys
    >>> stdin = sys.stdin
    >>> stdin.flush()
    >>> correct_stdin = io.TextIOWrapper(stdin.buffer, 'utf-8')
    >>> correct_stdin.readline()
    foobar
    'foobar\n'

    >>> correct_stdin.detach()
    <_io.BufferedReader name='<stdin>'>

    >>> del correct_stdin
    >>> stdin.readline()
    foobar
    'foobar\n'

I think detach is the correct way to to this, so I'm closing the issue.

Detach "destroys" the stream, so it's not a solution.  I can't just randomly destroy global state just because it's convenient.

This is what I am doing now which seems borderline insane: https://github.com/mitsuhiko/click/blob/master/click/_compat.py#L31

Ah. Misread.  This is about detaching the underlying stream from TextIOWrapper.  I assume this could be done in the __del__ so that would work.  I'm checking this now.

I can confirm that calling detach() in __del__ within an except block solves the issue.

I have a similar problem that text wrapper is closing the handle, and if I want to make a workaround, it also fails:

buffer = io.Bytes()
with io.TextIOWrapper(buffer, encoding='utf8') as text_buffer:
    write_content_to(text_buffer)
    text_buffer.flush()
    text_buffer.detach()

Now this fails when context manager is trying to close the text_buffer with an error that it is already detached. If I do not detach it, then it closes buffer as well.

In astropy we are now working around the auto-closing of the underlying stream in TextIOWrapper by subclassing and overriding `__del__` to detach [1]. It would seem more elegant if `TestIOWrapper` (and really, `BufferedReader`) could gain an `closefd` argument, just like `open` has, which is `True` by default.

p.s. Do let me know if it is better to open a new issue.

[1] https://github.com/astropy/astropy/pull/11809