livecd-rootfs/live-build/expand-task

#!/usr/bin/python3

import argparse
import glob
import os
import re

p = argparse.ArgumentParser()
p.add_argument('output_dir')
p.add_argument('flavour')
p.add_argument('task')
p.add_argument('what', choices=['packages', 'snaps'])
args = p.parse_args()

if args.what == 'snaps':
    ext = '.snaps'
else:
    ext = ''


# begin copy/paste from ubuntu-archive-publishing's generate_extra_overrides.
def parseTaskHeaders(seedtext):
    """Parse a seed for Task headers.

    seedtext is a file-like object.  Return a dictionary of Task headers,
    with keys canonicalised to lower-case.
    """
    task_headers = {}
    task_header_regex = re.compile(
        r"task-(.*?):(.*)", flags=re.IGNORECASE)
    for line in seedtext:
        match = task_header_regex.match(line)
        if match is not None:
            key, value = match.groups()
            task_headers[key.lower()] = value.strip()
    return task_headers

def getTaskSeeds(task_headers, seedname):
    """Return the list of seeds used to generate a task from this seed.

    The list of packages in this task comes from this seed plus any
    other seeds listed in a Task-Seeds header.
    """
    scan_seeds = set([seedname])
    if "seeds" in task_headers:
        scan_seeds.update(task_headers["seeds"].split())
    return sorted(scan_seeds)
# end copy/paste from ubuntu-archive-publishing's generate_extra_overrides.

# This is not quite the same as the one in generate_extra_overrides,
# because for seeds that do not have flavour specific names, the Task
# override is only generated for the Ubuntu flavour rather than
# redundantly doing it for each flavour.
def getTaskName(task_headers, flavour, seedname):
    """Work out the name of the Task to be generated from this seed.

    If there is a Task-Name header, it wins; otherwise, seeds with a
    Task-Per-Derivative get put in an appropriate namespace. Other seeds
    have a task name that matches the seed name.
    """
    if "name" in task_headers:
        return task_headers["name"]
    elif "per-derivative" in task_headers:
        return "%s-%s" % (flavour, seedname)
    else:
        return seedname


for seedtext in glob.glob(f'{args.output_dir}/*.seedtext'):
    hs = parseTaskHeaders(open(seedtext))
    if not hs:
        continue
    seedname = os.path.splitext(os.path.basename(seedtext))[0]
    tn = getTaskName(hs, args.flavour, seedname)
    if tn != args.task:
        continue
    for seed in getTaskSeeds(hs, seedname):
        for line in open(f'{args.output_dir}/{seed}{ext}'):
            if re.match('^[a-z0-9]', line):
                print(line.split()[0])
    break
else:
    raise Exception("did not find task %r" % (args.task,))