Parse buildout config into constraints and requirements. See https://community.plone.org/t/creating-constraints-and-requirements-from-buildout-config/10296

buildoutconfig2pip.py

# -*- coding: utf-8 -*-
# https://gist.github.com/mauritsvanrees/c47e974e418c707a626200cb6561405b
# https://community.plone.org/t/creating-constraints-and-requirements-from-buildout-config/10296
# from configparser import ConfigParser
from zc.buildout import buildout

import re


# We read this buildout config file:
configfile = "buildout.cfg"
# We cannot use configparser, because buildout configs contain 'duplicate' options:
# $ grep -i chameleon versions.cfg
# Chameleon = 3.6.2
# chameleon = 3.6.2
# So we use the buildout configparser:
config = buildout.Buildout(configfile, [])

# Get the constraints from the version pins.
# Ah, the versions get set directly on the config, nice!
# Note: this works like a dictionary, but is a class 'zc.buildout.buildout.Options'.
versions = config.versions
constraints_file = "parsed-constraints.txt"
with open(constraints_file, "w") as cfile:
    cfile.write("# Constraints parsed from {}\n".format(configfile))
    for package, version in sorted(versions.items()):
        cfile.write("{}=={}\n".format(package, version))
print("Wrote versions as constraints to {}.".format(constraints_file))

# Now for the requirements.
# We must avoid automatically downloading eggs, so we use the raw config.
config = config._raw
reqs = set(["zc.buildout"])
extensions = config["buildout"].get("extensions", "").split()
reqs.update(set(extensions))

# Regular expression for ${test:eggs}.
# Probably needs some tweaks, but works for now.
re_option_reference = re.compile(r"\${(.*):(.*)}")


def get_option_reference(text):
    # When text is ${test:eggs}, return ("test", "eggs").
    match = re_option_reference.match(text)
    if match is None:
        return
    return match.groups()


def read_eggs(section, option="eggs"):
    # Get the eggs.  Tricky is that these can be split on one line or on multiple lines.
    # And there can be extras, either "package[extra]" or "package [extra]",
    # making splitting harder.
    result = set()
    for line in config[section].get(option, "").splitlines():
        line = line.strip()
        if not line:
            continue
        # Get rid of spaces in front of an [extra].
        line = "[".join([part.strip() for part in line.split("[")])
        for egg in line.split():
            # Because we use the raw buildout config, we may have eggs like this:
            # ${test:eggs}
            ref = get_option_reference(egg)
            if not ref:
                result.add(egg)
                continue
            other_section, other_option = ref
            if other_section == ".":
                other_section = section
            eggs = read_eggs(other_section, other_option)
            result.update(eggs)

    return result


for section in config.keys():
    data = config[section]
    recipe = data.get("recipe")
    if recipe:
        reqs.add(recipe)
    # Get the eggs options.
    reqs.update(read_eggs(section))


requirements_file = "parsed-requirements.txt"
with open(requirements_file, "w") as rfile:
    rfile.write("# Requirements parsed from {}\n".format(configfile))
    for package in sorted(reqs):
        rfile.write("{}\n".format(package))
print("Wrote requirements to {}.".format(requirements_file))