Hi apt and devscripts maintainers, Tools parsing deb822-style documents currently disagree about where paragraphs should be split within the document. The result is that wrap-and-sort from devscripts currently eats control files if there are separator lines between paragraphs that contain whitespace, while the rest of our build system accepts whitespace-only lines as separators.
wrap-and-sort uses python-debian's deb822 module to work out what's in
debian/control so bugs about wrap-and-sort's behaviour here have ended up with
python-debian. I've sought to address this problem and attached is a patch for
python-debian that fixes it by explicitly including whitespace in python-
debian's test for new lines between paragraphs.
The problem with this patch is that python-debian's deb822 parser isn't
necessarily used by devscripts... python-debian will use python-apt's
apt_pkg.TagFile if it is available and it also has this same behaviour. If I
were to apply this patch to python-debian, there would be different behaviour
depending on whether python-apt is installed and whether the text being
interpreted is a file or a sequence/string:
* if python-apt is not installed or the text is not a file or the call to
iter_paragraphs includes "use_apt_pkg=False", then the code path in
deb822.py is used and the split is done correctly. Using the same test
case as in #655988 where the correct answer should be '3':
$ python -c 'import deb822; print len([p for p in
deb822.Deb822.iter_paragraphs(open("control-wspace"), use_apt_pkg=False)])'
3
$ python -c 'import deb822; print len([p for p in
deb822.Deb822.iter_paragraphs(open("control-wspace").readlines())])'
3
* if python-apt is installed and the text is in a file and "use_apt_pkg=False"
is not given, then libapt will *not* split the paragraphs as desired.
$ python -c 'import deb822; print len([p for p in
deb822.Deb822.iter_paragraphs(open("control-wspace"))])'
2
:(
So... we could change python-debian with the attached patch and *also* change
devscripts/control.py to pass "use_apt_pkg=False" and that would fix wrap-and-
sort.
However, making those two changes alone would mean that the use of
apt_pkg.TagFile is not just a performance boost for iter_paragraphs as
advertised in its documentation, it will also have different behaviour. I don't
think that's a particularly good idea. It's creating a horrible interface and
potentially making for very difficult debugging for other users of deb822.py.
python-apt maintainers: do you think it's reasonable to change apt_pkg.TagFile
(presumably by changing libapt-pkg) to split paragraphs not only on blank
lines but also on whitespace-only lines? For reference, policy §5.1 permits
such control files with pretty rubbery language:
The paragraphs are separated by empty lines. Parsers may accept lines
consisting solely of spaces and tabs as paragraph separators, but control
files should use empty lines.
I tend to err on the side of the parser being lax and the generator being
strict, which makes me think that both deb822.iter_paragraphs and
apt_pkg.TagFile should split on these whitespace-only lines.
cheers
Stuart
--
Stuart Prescott http://www.nanonanonano.net/ stu...@nanonanonano.net
Debian Developer http://www.debian.org/ stu...@debian.org
GPG fingerprint 90E2 D2C1 AD14 6A1B 7EBB 891D BBC1 7EBB 1396 F2F7
From c8bbd5a9776fa03811ef11f73aa598059f64e002 Mon Sep 17 00:00:00 2001
From: Stuart Prescott <stu...@debian.org>
Date: Wed, 4 Jun 2014 00:49:01 +1000
Subject: [PATCH] Allow whitespace-only lines to separate paragraphs
iter_paragraphs should split paragraphs on whitespace-only lines.
Paragraphs should be separated by a blank line but policy permits parsers to
permit whitespace only lines too.
Closes #715558.
---
lib/debian/deb822.py | 4 +++-
tests/test_deb822.py | 24 ++++++++++++++++++++++++
2 files changed, 27 insertions(+), 1 deletion(-)
diff --git a/lib/debian/deb822.py b/lib/debian/deb822.py
index 98bf9f3..ed933e4 100644
--- a/lib/debian/deb822.py
+++ b/lib/debian/deb822.py
@@ -627,7 +627,9 @@ class Deb822(Deb822Dict):
gpg_post_lines = []
state = b'SAFE'
gpgre = re.compile(br'^-----(?P<action>BEGIN|END) PGP (?P<what>[^-]+)-----$')
- blank_line = re.compile(b'^$')
+ # Include whitespace-only lines in blank lines to split paragraphs.
+ # (see #715558)
+ blank_line = re.compile(b'^\s*$')
first_line = True
for line in sequence:
diff --git a/tests/test_deb822.py b/tests/test_deb822.py
index a989a32..614bd5a 100755
--- a/tests/test_deb822.py
+++ b/tests/test_deb822.py
@@ -445,6 +445,30 @@ class TestDeb822(unittest.TestCase):
self.assertWellParsed(d, PARSED_PACKAGE)
self.assertEqual(count, 2)
+ def test_iter_paragraphs_with_extra_whitespace(self):
+ """ Paragraphs not elided when stray whitespace is between
+
+ From policy §5.1:
+
+ The paragraphs are separated by empty lines. Parsers may accept
+ lines consisting solely of spaces and tabs as paragraph separators,
+ but control files should use empty lines.
+
+ On the principle of "be strict in what you send; be generous in
+ what you receive", deb822 should permit such extra whitespace between
+ deb822 stanzas.
+
+ See #715558 for further details.
+ """
+ for extra_space in (" ", " ", "\t"):
+ text = (UNPARSED_PACKAGE + '%s\n' % extra_space
+ + UNPARSED_PACKAGE).splitlines()
+ count = 0
+ for d in deb822.Deb822.iter_paragraphs(text):
+ count += 1
+ self.assertEqual(count, 2,
+ "Wrong number paragraphs were found: %d != 2" % count)
+
def _test_iter_paragraphs(self, filename, cls, **kwargs):
"""Ensure iter_paragraphs consistency"""
--
1.9.1
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