[Python-Dev] opinions on issue2142 ('\ No newline at end of file' to difflib.unified_diff)? (original) (raw)

Trent Mick trentm at gmail.com
Thu Oct 7 00:53:59 CEST 2010

Soliciting opinions on issue 2142 (http://bugs.python.org/issue2142). There are patched available so this isn't vapour. :)

The issue is this (I'll discuss only unified_diff(), but the same applies to context_diff()):

from difflib import * gen = unifieddiff("one\ntwo\nthree".splitlines(1), ... "one\ntwo\ntrois".splitlines(1)) print ''.join(gen)

+++ @@ -1,3 +1,3 @@ one two -three+trois

Where as with diff, hg and git:

diff -r 667b0870428d a --- a/a Wed Oct 06 15:39:50 2010 -0700 +++ b/a Wed Oct 06 15:40:31 2010 -0700 @@ -1,3 +1,3 @@ one two -three \ No newline at end of file +trois \ No newline at end of file

While originally marked as a bug, the issue was changed to be a feature request, because arguably difflib.unified_diff() is fine, and the problem is in the naive use of the following to create a patch that will work with patch:

''.join(gen)

Possiblities:

  1. Change difflib.unified_diff to emit:

    ['--- \n', '+++ \n', '@@ -1,3 +1,3 @@\n', ' one\n', ' two\n',

'-three\n', '\ No newline at end of file', '+trois\n', '\ No newline at end of file']

instead of:

['---  \n', '+++  \n', '@@ -1,3 +1,3 @@\n', ' one\n', ' two\n',

'-three', '+trois']

for this case.

  1. Add a add_end_of_file_newline_markers_to_make_patch_happy keyword arg (probably with a different name:) to difflib.unified_diff to do this additional handling. The reason is to not surprise existing code that would be surprised with those "\No newline at end of file" entries.

  2. Not touch difflib.unified_diff and instead update http://docs.python.org/library/difflib.html#difflib-interface documentation to discuss the issue and show how users of unified_diff should handle this case themselves.

Thoughts?

Orthogonal: After a decision is made for the Python 3.3 tree we can discuss if including this in either of Python 2.7 or 3.2 would be wanted.

-- Trent Mick

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