Bug#875306: python-debian: include a type for buildinfo files

[Stuart Prescott]

Dear reproducible-builds folks,

python-debian has classes to wrap many of Debian's deb822 format files, trying 
to use an underlying parser that always exposes the data in more or less the 
same key/value way via a dictionary, plus also providing extra syntactic sugar 
to help make sense of the values that are included. For example, package 
dependencies such as Depends or Build-Depends are split up into a list of 
relationships, with the standard syntax that we use everywhere interpreted to 
include version restrictions etc.

The .buildinfo files have two places where interpreting the values seems 
worthwhile:

	Environment: split the lines and extract the key="value" data into a
	dictionary in the same format as Python's normal `os.environ`. (Some
	dequoting is needed but not currently implemented.)

	Installed-Build-Depends: use the standard package-relation code on this to
	return interpret the list of packages.

We could thus do something like:

In [1]: from debian import deb822

In [2]: info = deb822.BuildInfo(open("debian/tests/test_BuildInfo"))

In [3]: info.get_environment()
Out[3]: 
{'DEB_BUILD_OPTIONS': 'parallel=4',
 'LANG': 'en_AU.UTF-8',
 'LC_ALL': 'C.UTF-8',
 'LC_TIME': 'en_GB.UTF-8',
 'LD_LIBRARY_PATH': '/usr/lib/libeatmydata',
 'SOURCE_DATE_EPOCH': '1601784586'}

In [4]: info.relations['installed-build-depends']
Out[4]: 
[[{'name': 'autoconf',
   'archqual': None,
   'version': ('=', '2.69-11.1'),
   'arch': None,
   'restrictions': None}],
 [{'name': 'automake',
   'archqual': None,
   'version': ('=', '1:1.16.2-4'),
   'arch': None,
   'restrictions': None}],
 [{'name': 'autopoint',
   'archqual': None,
   'version': ('=', '0.19.8.1-10'),
   'arch': None,
   'restrictions': None}],
 [{'name': 'autotools-dev',
   'archqual': None,
   'version': ('=', '20180224.1'),
   'arch': None,
   'restrictions': None}],
 [{'name': 'base-files',
   'archqual': None,
   'version': ('=', '11'),
   'arch': None,
   'restrictions': None}],
...(trimmed)...

In [5]: for dep in info.relations['installed-build-depends']:
   ...:     print("Installed %s/%s" % (dep[0]['name'], dep[0]['version'][1]))
   ...:     
Installed autoconf/2.69-11.1
Installed automake/1:1.16.2-4
Installed autopoint/0.19.8.1-10
Installed autotools-dev/20180224.1
Installed base-files/11
...(trimmed)...


The standard format for the list of package relationships contains features 
that the buildinfo format doesn't need ("foo | bar", architecture and build-
profile restrictions), but it seems better to use exactly the same format as is 
used for Packages and Sources. That does however mean there are lots of 
single-element lists used, as seen in the `dep[0]` usage above. A bit ugly, 
but consistency wins here, I think.

How does this look to you?

Are there additional data that would be nice to extract and interpret in a 
structured way?

The current code doesn't handle dequoting the environment values and will 
react particularly badly to environment values with newlines in them.

The current work-in-progress code is at 

https://salsa.debian.org/python-debian-team/python-debian/-/merge_requests/29

Comments, suggestions and encouragement gratefully accepted :)

thanks
Stuart

-- 
Stuart Prescott    http://www.nanonanonano.net/   stuart at nanonanonano.net
Debian Developer   http://www.debian.org/         stuart at debian.org
GPG fingerprint    90E2 D2C1 AD14 6A1B 7EBB 891D BBC1 7EBB 1396 F2F7