Bug#881826: devscripts: sadt: does not parse debian/control with comments

[Geoffrey Thomas]

Package: devscripts
Version: 2.17.11
User: devscripts at packages.debian.org
Usertags: sadt

sadt fails to correctly parse debian/control files that include comments 
in their build-dependencies, for instance:

$ mkdir -p debian/tests
$ cat > debian/control << EOF
Source: s
Build-Depends:
# some comment here
  sl
EOF
$ cat > debian/tests/control << EOF
Tests: sl-exists
Depends: @builddeps@
EOF
$ cat > debian/tests/sl-exists << EOF
#!/bin/sh
dpkg -l sl
EOF
$ sadt
Traceback (most recent call last):
   File "/usr/bin/sadt", line 476, in <module>
     main()
   File "/usr/bin/sadt", line 378, in main
     for n, para in enumerate(deb822.Packages.iter_paragraphs(file)):
   File "/usr/lib/python3/dist-packages/debian/deb822.py", line 378, in iter_paragraphs
     for section in parser:
apt_pkg.Error: E:Unable to parse package file  (1)

This is refused by libapt-pkg's deb822 format parser, but permitted by the 
pure-Python one in python-debian, as noted in a comment in python-debian:

> :param use_apt_pkg: if sequence is a file, apt_pkg can be used
>    if available to parse the file, since it's much much faster.  Set
>    this parameter to True to enable use of apt_pkg. Note that the
>    TagFile parser from apt_pkg is a much stricter parser of the
>    Deb822 format, particularly with regards whitespace between
>    paragraphs and comments within paragraphs. If these features are
>    required (for example in debian/control files), ensure that this
>    parameter is set to False.

The "Packages" subclass (which is intended for parsing Packages files in 
apt repos, not deb822 files in general) sets use_apt_pkg to true. The 
simplest fix is to change sadt line 378 to pass use_apt_pkg=False, but in 
theory, python-debian should gain a new subclass for debian/control files 
that has the _PkgRelationMixin but uses the more lenient parser.

If you would like me to commit this change to the collab-maint repo, let 
me know. I've confirmed that it does fix the problem.

-- 
Geoffrey Thomas
https://ldpreload.com
geofft at ldpreload.com