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Title: readline: Wrong tab completion scope indices in Unicode terminals
Type: behavior Stage: resolved
Components: Library (Lib), Unicode Versions: Python 3.6, Python 3.5
Status: closed Resolution: fixed
Dependencies: Superseder:
Assigned To: Nosy List: ezio.melotti, kunkku, lemburg, loewis, martin.panter, python-dev, serhiy.storchaka, vstinner
Priority: normal Keywords: patch

Created on 2012-10-09 20:09 by kunkku, last changed 2022-04-11 14:57 by admin. This issue is now closed.

File name Uploaded Description Edit
readline-wide-char-index.patch kunkku, 2012-10-09 20:09 Patch for adjusting the scope indices review
readline_locale.patch serhiy.storchaka, 2016-05-23 06:02 review
readline_locale.v2.patch martin.panter, 2016-05-31 13:53 review
readline_locale.v3.patch martin.panter, 2016-06-02 09:46 review
readline_locale.v4.patch martin.panter, 2016-06-12 10:57 review
Messages (18)
msg172517 - (view) Author: Kaarle Ritvanen (kunkku) * Date: 2012-10-09 20:09
Tab completion in the readline module does not seem to work well with Unicode terminals. The get_line_buffer function converts the line buffer to the str type (which are Unicode strings in Python 3), but the indices returned by get_begidx and get_endidx are not adjusted with respect to possible wide characters in the buffer, and hence are not very useful. The documentation is a bit vague on the index functions, but I think they should be relative to code points, regardless of the encoding used by the C library. The suggested correction is attached.

My second point of complaint is related to the use of PyUnicode_FromString in the module. The strings returned by the readline library use the current locale encoding, which is not necessarily UTF-8. I wonder if PyUnicode_DecodeLocale should be used instead for more portable code.
msg223105 - (view) Author: Mark Lawrence (BreamoreBoy) * Date: 2014-07-15 13:00
@Kaarle please accept our apologies for the delay in getting back to you.  Can one of our unicode gurus comment please.
msg266124 - (view) Author: Serhiy Storchaka (serhiy.storchaka) * (Python committer) Date: 2016-05-23 06:02
Yes, the readline module is broken in Python 3. Underlying C library operates C strings and use locale-depended C functions to split it on Unicode characters. The Python wrapper always uses the UTF-8 encoding for converting between Python strings and C strings. It works only on UTF-8 locales. get_begidx() and get_endidx() don't correctly work at all for non-ASCII data. We should use locale encoding for converting.

Proposed patch makes the readline module to use locale depending coding functions instead of default UTF-8. It also corrects indices for get_begidx() and get_endidx().
msg266318 - (view) Author: Martin Panter (martin.panter) * (Python committer) Date: 2016-05-25 07:43
I’m a bit worried about flex_complete() covering up errors. If I add calls to PyErr_WriteUnraisable(), I can see both the s1 and s2 decodes failing. Input the following line:

>>> "©"; import x;

and then move the cursor back one place, so it is directly after the “x”, but not after the semicolon (;). Then press Tab. Both errors are:

ValueError: embedded null byte

It looks like the reason is that PyUnicode_DecodeLocaleAndSize() requires that str[len] is a null character (the error message is misleading). It seems the len parameter is mainly there to verify that there are no embedded null characters, i.e. you cannot use it to give a truncated string.

It looks like Py_DecodeLocale() is used underneath; maybe it is simpler to call that directly. But it does not solve the string truncating problem.

A test case (perhaps using a pseudo-terminal) might also help pick this kind of thing up, if we can’t report errors any other way.
msg266752 - (view) Author: Martin Panter (martin.panter) * (Python committer) Date: 2016-05-31 13:51
Attached patch adds a possible test, and fixes the truncation problem I mentioned above.

I tried testing set_completer_delims() with a UTF-8 locale, but I suspect Gnu Readline does not support it. I called set_completer_delims("\xF6"), which encodes as C3 B6, but it seems to be breaking any UTF-8 sequence in half at a C3 byte. In other words, it is treating the delimiter list as a list of bytes, not code points. So I changed to an ASCII delimiter.
msg266881 - (view) Author: Martin Panter (martin.panter) * (Python committer) Date: 2016-06-02 09:46
V3 finishes what I started in v2:

* Changed unchecked PyBytes_AsString() → PyBytes_AS_STRING()
* Testing more functions for non-ASCII characters

I tried to test it with Editline on Linux (using my patch for Issue 13501). There seem to be many quirks with my version of Editline, some of which are not easy to work around:

* Initial CR swallowed when entering non-ASCII
* set_completion_display_matches_hook(), set_pre_input_hook(), set_completer_delims() all do nothing useful
* get_history_item() not updated straight after read_history_file()

I suspect Apple has patched their version of Editline, but if these quirks exist on Apple as well, it might be simplest to skip the test for Editline.
msg267070 - (view) Author: Serhiy Storchaka (serhiy.storchaka) * (Python committer) Date: 2016-06-03 07:22
Thank you for your comments and updated patches, and especially for tests Martin. Added some comments on Rietveld.
msg268230 - (view) Author: Serhiy Storchaka (serhiy.storchaka) * (Python committer) Date: 2016-06-11 16:40
msg268361 - (view) Author: Martin Panter (martin.panter) * (Python committer) Date: 2016-06-12 10:57
I updated the patch to fix the error handling and memory leak. it also now skips the test in case the locale cannot encode the test data.
msg268374 - (view) Author: Serhiy Storchaka (serhiy.storchaka) * (Python committer) Date: 2016-06-12 13:15

But the test fails with PYTHONIOENCODING=ascii.

$ PYTHONIOENCODING=ascii ./python -m test test_readline
Run tests sequentially
0:00:00 [1/1] test_readline
test test_readline failed -- Traceback (most recent call last):
  File "/home/serhiy/py/cpython/Lib/test/", line 194, in test_nonascii
    self.assertIn(b"result " + expected + b"\r\n", output)
AssertionError: b"result '[\\xefnserted]|t\\xebxt[after]'\r\n" not found in bytearray(b'^A^B^B^B^B^B^B^B\t\tx\t\r\n[\xc3\xafnserted]|t\xc3\xab[after]\x08\x08\x08\x08\x08\x08\x08text \'t\\xeb\'\r\nline \'[\\xefnserted]|t\\xeb[after]\'\r\nindexes 11 13\r\n\x07text \'t\\xeb\'\r\nline \'[\\xefnserted]|t\\xeb[after]\'\r\nindexes 11 13\r\nsubstitution \'t\\xeb\'\r\nmatches [\'t\\xebnt\', \'t\\xebxt\']\r\nx[after]\x08\x08\x08\x08\x08\x08\x08t[after]\x08\x08\x08\x08\x08\x08\x08\r\nTraceback (most recent call last):\r\n  File "<string>", line 39, in <module>\r\nUnicodeDecodeError: \'ascii\' codec can\'t decode byte 0xc3 in position 1: ordinal not in range(128)\r\n')

This is minor problem, since buildbots rarely configured with PYTHONIOENCODING=ascii.
msg268499 - (view) Author: Martin Panter (martin.panter) * (Python committer) Date: 2016-06-14 01:44
I get two other test suite failures if I set PYTHONIOENCODING, so I am not going to bother addressing this in test_readline :)

FAIL: test_forced_io_encoding (test.test_capi.EmbeddingTests)
FAIL: test_7 (test.test_pkg.TestPkg)
msg268506 - (view) Author: Roundup Robot (python-dev) (Python triager) Date: 2016-06-14 03:03
New changeset 5122b3465a38 by Martin Panter in branch '3.5':
Issue #16182: Fix readline begidx, endidx, and use locale encoding

New changeset 2ae2657d87a6 by Martin Panter in branch 'default':
Issue #16182: Merge readline locale fix from 3.5
msg268522 - (view) Author: Martin Panter (martin.panter) * (Python committer) Date: 2016-06-14 05:50
Failures from AMD64 Snow Leop buildbots:

FAIL: test_nonascii_history (test.test_readline.TestHistoryManipulation)
Traceback (most recent call last):
  File "/Users/buildbot/buildarea/3.5.murray-snowleopard/build/Lib/test/", line 102, in test_nonascii_history
    self.assertEqual(readline.get_history_item(1), "entrée 1")
AssertionError: None != 'entrée 1'

FAIL: test_nonascii (test.test_readline.TestReadline)
Traceback (most recent call last):
  File "/Users/buildbot/buildarea/3.5.murray-snowleopard/build/Lib/test/", line 174, in test_nonascii
    self.assertIn(b"line '[\\xefnserted]|t\\xeb[after]'\r\n", output)
AssertionError: b"line '[\\xefnserted]|t\\xeb[after]'\r\n" not found in bytearray(b"^A^B^B^B^B^B^B^B\t\tx\t\r\n|t\xc3\xab[after]\x08\x08\x08\x08\x08\x08\x08text \'t\\xeb\'\r\nline \'|t\\xeb[after]\'\r\nindexes 1 3\r\n\x07text \'t\\xeb\'\r\nline \'|t\\xeb[after]\'\r\nindexes 1 3\r\n\r\nt\xc3\xabxt  t\xc3\xabnt  \r\n\r\r\n|t\xc3\xab[after]\r|t\xc3\xabx[after]\r|t\xc3\xabxt[after]\r|t\xc3\xabxt\r\nresult \'|t\\xebxt[after]\'\r\nhistory \'|t\\xebxt[after]\'\r\n")
msg268523 - (view) Author: Roundup Robot (python-dev) (Python triager) Date: 2016-06-14 05:51
New changeset 0794bbfceec6 by Martin Panter in branch '3.5':
Issue #16182: Attempted workarounds for Apple Editline

New changeset a1ca9c0ebc05 by Martin Panter in branch 'default':
Issue #16182: Merge test_readline from 3.5
msg268541 - (view) Author: Martin Panter (martin.panter) * (Python committer) Date: 2016-06-14 08:00
Also need a fix for missing set_pre_input_hook() on the AIX buildbot:

FAIL: test_nonascii (test.test_readline.TestReadline)
Traceback (most recent call last):
  File "/home/shager/cpython-buildarea/3.5.edelsohn-aix-ppc64/build/Lib/test/", line 173, in test_nonascii
    self.assertIn(b"text 't\\xeb'\r\n", output)
AssertionError: b"text 't\\xeb'\r\n" not found in bytearray(b'\x01\x02\x02\x02\x02\x02\x02\x02                x       \r\n\x1b[?1034hTraceback (most recent call last):\r\n  File "<string>", line 18, in <module>\r\nAttributeError: module \'readline\' has no attribute \'set_pre_input_hook\'\r\n')
msg268545 - (view) Author: Roundup Robot (python-dev) (Python triager) Date: 2016-06-14 09:02
New changeset 005cab4f5629 by Martin Panter in branch '3.5':
Issue #16182: set_pre_input_hook() may not exist; document, and update test

New changeset c4dd384ee3fa by Martin Panter in branch 'default':
Issue #16182: Merge readline update from 3.5

New changeset cff695a0b449 by Martin Panter in branch '2.7':
Issue #16182: Backport documentation of set_pre_input_hook() availability
msg268549 - (view) Author: Roundup Robot (python-dev) (Python triager) Date: 2016-06-14 11:37
New changeset ef234a5c5817 by Martin Panter in branch '3.5':
Issue #16182: One more check for set_pre_input_hook()

New changeset 241bae60cef8 by Martin Panter in branch 'default':
Issue #16182: Merge test_readline from 3.5
msg268598 - (view) Author: Martin Panter (martin.panter) * (Python committer) Date: 2016-06-15 01:08
Think I got all the bugs fixed here.
Date User Action Args
2022-04-11 14:57:37adminsetgithub: 60386
2016-06-15 01:08:50martin.pantersetstatus: open -> closed
resolution: fixed
messages: + msg268598

stage: patch review -> resolved
2016-06-14 11:37:20python-devsetmessages: + msg268549
2016-06-14 09:02:09python-devsetmessages: + msg268545
2016-06-14 08:00:21martin.pantersetmessages: + msg268541
2016-06-14 05:51:15python-devsetmessages: + msg268523
2016-06-14 05:50:29martin.pantersetmessages: + msg268522
2016-06-14 03:03:43python-devsetnosy: + python-dev
messages: + msg268506
2016-06-14 01:44:25martin.pantersetmessages: + msg268499
2016-06-12 13:15:50serhiy.storchakasetmessages: + msg268374
2016-06-12 10:57:35martin.pantersetfiles: + readline_locale.v4.patch

messages: + msg268361
2016-06-11 16:40:54serhiy.storchakasetmessages: + msg268230
2016-06-03 07:22:37serhiy.storchakasetmessages: + msg267070
2016-06-02 09:46:05martin.pantersetfiles: + readline_locale.v3.patch

messages: + msg266881
2016-05-31 13:53:07martin.pantersetfiles: + readline_locale.v2.patch
2016-05-31 13:52:46martin.pantersetfiles: - readline_locale.v2.patch
2016-05-31 13:51:44martin.pantersetfiles: + readline_locale.v2.patch

messages: + msg266752
2016-05-28 21:11:56BreamoreBoysetnosy: - BreamoreBoy
2016-05-25 08:03:01martin.panterlinkissue25419 dependencies
2016-05-25 07:43:02martin.pantersetmessages: + msg266318
2016-05-23 06:02:47serhiy.storchakasetfiles: + readline_locale.patch
versions: + Python 3.6, - Python 3.4
nosy: + martin.panter

messages: + msg266124
2015-10-17 14:44:55serhiy.storchakasetnosy: + serhiy.storchaka
2014-07-15 13:00:38BreamoreBoysetversions: + Python 3.5, - Python 3.2, Python 3.3
nosy: + BreamoreBoy, ezio.melotti, lemburg, loewis

messages: + msg223105

components: + Unicode
2012-10-09 20:18:27pitrousetnosy: + vstinner
stage: patch review

versions: + Python 3.4
2012-10-09 20:09:44kunkkucreate