https://bz.mercurial-scm.org/show_bug.cgi?id=5807
Bug ID: 5807
Summary: Convert throws "ValueError: I/O operation on closed
file"
Product: Mercurial
Version: 4.2
Hardware: PC
OS: Linux
Status: UNCONFIRMED
Severity: bug
Priority: wish
Component: convert
Assignee: bugzi...@mercurial-scm.org
Reporter: neme...@wienfluss.net
CC: duri...@gmail.com, mercurial-devel@mercurial-scm.org
= Background =
Due to a recent system upgrade on one of our machines (openSuSE 42.2 -> 42.3),
mercurial was updated from 3.8.3 to 4.2.3. After that, our script to fetch,
update and convert a remote SVN repo into our local HG mirror throws the
following error:
> ** Unknown exception encountered with possibly-broken third-party extension
> prompt
> ** which supports versions unknown of Mercurial.
> ** Please disable prompt and try your action again.
> ** If that fixes the bug please report it to the extension author.
> ** Python 2.7.13 (default, Jan 03 2017, 17:41:54) [GCC]
> ** Mercurial Distributed SCM (version 4.2.3)
> ** Extensions loaded: convert, extdiff, churn, prompt
> Traceback (most recent call last):
> File "/usr/bin/hg", line 45, in <module>
> mercurial.dispatch.run()
> File "/usr/lib64/python2.7/site-packages/mercurial/dispatch.py", line 83,
> in run
> status = (dispatch(req) or 0) & 255
> File "/usr/lib64/python2.7/site-packages/mercurial/dispatch.py", line 178,
> in dispatch
> req.ui.flush()
> File "/usr/lib64/python2.7/site-packages/mercurial/ui.py", line 823, in
> flush
> self.fout.flush()
> ValueError: I/O operation on closed file
= Findings =
1. Disabling the prompt extension did not improve the situation (same error
persists).
2. We tested with the following versions:
- 3.8.3-2.11.1: worked prior upgrade
- 4.2-1.2: throws error shown above
- 4.2.3-7.1: throws error shown above
- 4.5-202.2: throws error shown above
3. Error suggests that the targeted file or buffer is closed prematurely. Even
when inserting a python debug before the self.fout.flush() statement, the error
is triggered.
4. After investigating the code, I think the problem stems from changeset
30261:6bed17ba00a1 (see
https://www.mercurial-scm.org/repo/hg/rev/6bed17ba00a1). It replaced sys.stdin
/ sys.stdout with ui.fin / ui.fout. But it did not take into consideration,
that the buffer automatically is closed in "get_log_child()".
= Proposed change =
In "get_log_child()", I would simply replace the fp.close() with fp.flush().
This will ensure that the buffer is still available.
I'll submit a patch to mercurial-devel@mercurial-scm.org soonish.
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