Some applications (e.g. traditional Unix diff, version control
systems) neither know nor care about the encodings of the files they
are comparing. They are textual, but to the diff utility they are just
bytes. This worked fine under Python 2, because all of the hardcoded
strings in difflib.py are ASCII, so could safely be combined with
old-style u'' strings. But it stopped working in 3.x.
The solution is to use surrogate escapes for a lossless
bytes->str->bytes roundtrip. That means {unified,context}_diff() can
continue to just handle strings without worrying about bytes. Callers
who have to deal with bytes will need to change to using diff_bytes().
Use case: Mercurial's test runner uses difflib to compare current hg
output with known good output. But Mercurial's output is just bytes,
since it can contain:
* file contents (arbitrary unknown encoding)
* filenames (arbitrary unknown encoding)
* usernames and commit messages (usually UTF-8, but not guaranteed
because old versions of Mercurial did not enforce it)
* user messages (locale encoding)
Since the output of any given hg command can include text in multiple
encodings, it is hopeless to try to treat it as decodable Unicode
text. It's just bytes, all the way down.
This is an elaboration of a patch by Terry Reedy.
svn+ssh://pythondev@svn.python.org/python/trunk
........
r80004 | r.david.murray | 2010-04-12 12:35:19 -0400 (Mon, 12 Apr 2010) | 13 lines
Issue #7585: use tab between components in unified and context diff headers.
Instead of spaces between the filename and date (or whatever the string
is that follows the filename, if any) use tabs. This is what the unix
'diff' command does, for example, and difflib was intended to follow
the 'standard' way of doing diffs. This improves compatibility with
patch tools. The docs and examples are also changed to recommended that
the date format used be the ISO 8601 format, which is what modern diff
tools emit by default.
Patch by Anatoly Techtonik.
........
svn+ssh://pythondev@svn.python.org/python/trunk
........
r62490 | benjamin.peterson | 2008-04-24 20:29:10 -0500 (Thu, 24 Apr 2008) | 2 lines
reformat some documentation of classes so methods and attributes are under the class directive
........
