Bug#1036731: python3-debian: fails to parse some debian/control.in files

[Dylan Aïssi]

Package: python3-debian
Version: 0.1.49

Hello,

python3-debian is not able anymore to parse correctly some debian/control.in.
The first version with this issue is 0.1.44, so I suppose it is related to the
new RTS parser. The consequence of this bug is wrap-and-sort crashes when it
run on these files. Below is the error message:

Traceback (most recent call last):
  File "/usr/bin/wrap-and-sort", line 496, in <module>
    main()
  File "/usr/bin/wrap-and-sort", line 481, in main
    modified_files = wrap_and_sort(args)
                     ^^^^^^^^^^^^^^^^^^^
  File "/usr/bin/wrap-and-sort", line 312, in wrap_and_sort
    control = WrapAndSortControl(control_file, args)
              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/bin/wrap-and-sort", line 99, in __init__
    super().__init__(filename, use_rts_parser=args.rts_parser)
  File "/usr/lib/python3/dist-packages/devscripts/control.py", line
210, in __init__
    self._deb822_file = parse_deb822_file(sequence)
                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3/dist-packages/debian/_deb822_repro/parsing.py",
line 3095, in parse_deb822_file
    deb822_file = Deb822FileElement(LinkedList(tokens))
                                    ^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3/dist-packages/debian/_util.py", line 159, in __init__
    self.extend(values)
  File "/usr/lib/python3/dist-packages/debian/_util.py", line 272, in extend
    for v in values:
  File "/usr/lib/python3/dist-packages/debian/_deb822_repro/_util.py",
line 104, in _impl
    for token in token_stream:
  File "/usr/lib/python3/dist-packages/debian/_deb822_repro/_util.py",
line 104, in _impl
    for token in token_stream:
  File "/usr/lib/python3/dist-packages/debian/_deb822_repro/parsing.py",
line 2991, in _build_field_with_value
    value_element = next(buffered_stream, None)
                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3/dist-packages/debian/_deb822_repro/_util.py",
line 143, in __next__
    return next(self._stream)
           ^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3/dist-packages/debian/_deb822_repro/_util.py",
line 104, in _impl
    for token in token_stream:
  File "/usr/lib/python3/dist-packages/debian/_deb822_repro/parsing.py",
line 2939, in _build_value_line
    tokens_in_value = list(buffered_stream.takewhile(_non_end_of_line_token))
                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3/dist-packages/debian/_deb822_repro/_util.py",
line 149, in takewhile
    while buffer or self._fill_buffer(5):
                    ^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3/dist-packages/debian/_deb822_repro/_util.py",
line 198, in _fill_buffer
    self._buffer.append(next(self._stream))
                        ^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3/dist-packages/debian/_deb822_repro/_util.py",
line 104, in _impl
    for token in token_stream:
  File "/usr/lib/python3/dist-packages/debian/_deb822_repro/parsing.py",
line 3031, in _abort_on_error_tokens
    raise SyntaxOrParseError(
debian._deb822_repro.types.SyntaxOrParseError: Syntax or Parse error
on the line: "%if USE_SYSTEM_ZLIB\n"

An easy way to reproduce the crash is to run wrap-and-sort on the
debian/ folder of
firefox-esr:
> wget http://deb.debian.org/debian/pool/main/f/firefox-esr/firefox-esr_102.11.0esr-1.debian.tar.xz
> tar -xvf firefox-esr
> wrap-and-sort

It crashes in a similar way on these packages: babel-minify and xapian-bindings.

Best regards,
Dylan