Use the django ORM for filters instead of a custom SQL query generator

[rmoorman]

While trying to use django-scim2 in a project, I noticed, that the default UserFilterQuery uses a custom SQL query building class under the hood. This is also the case for the default GroupFilterParser. It could also very well be that I overlooked something.

Anyway, I tried to work around this by using a custom filter parsers, would like to share what I tried, and could currently see no better option than filing an issue here 🙂.

The custom parsers look something like this (everything that was needed seemed to be already there in the scim2_filter_parser):

from scim2_filter_parser.lexer import SCIMLexer
from scim2_filter_parser.parser import SCIMParser
from scim2_filter_parser.transpilers.django_q_object import Transpiler as SCIMTranspiler

class CustomFilterParserBase:
    attr_map = {}

    @classmethod
    def search(cls, query, request=None):
        return cls.query_to_qs(query, cls.attr_map)

    @staticmethod
    def query_to_qs(query, attr_map):
        tokens = SCIMLexer().tokenize(query)
        ast = SCIMParser().parse(tokens)
        qs = SCIMTranspiler(attr_map).transpile(ast)
        return qs


class UserFilterParser(CustomFilterParserBase):
    attr_map = {
        # attr, sub attr, uri
        ("externalId", None, None): "userlicense__external_user_id",
        ("userName", None, None): "username",
        ("name", "familyName", None): "last_name",
        ("familyName", None, None): "last_name",
        ("name", "givenName", None): "first_name",
        ("givenName", None, None): "first_name",
        ("active", None, None): "is_active",
    }


class GroupFilterParser(CustomFilterParserBase):
    attr_map = {
        # attr, sub attr, uri
        ("externalId", None, None): "external_group_id",
        ("displayName", None, None): "name",
        # ("userName", None, None): "username",
        # ("name", "familyName", None): "last_name",
        # ("familyName", None, None): "last_name",
        # ("name", "givenName", None): "first_name",
        # ("givenName", None, None): "first_name",
        # ("active", None, None): "is_active",
    }

I set them in the SCIM_SERVICE_PROVIDER configuration within settings.py like this:

SCIM_SERVICE_PROVIDER = {
    # ...
    "USER_FILTER_PARSER": "my_scim.filters.UserFilterParser",
    "GROUP_FILTER_PARSER": "my_scim.filters.GroupFilterParser",
    # ...
}

And I have a custom UsersView and GroupsView that look something like this:

import json
from django_scim import constants
from django_scim import exceptions as scim_exceptions
from django_scim import views
from scim2_filter_parser.parser import SCIMParserError

class CustomFilterMixin:
    def _search(self, request, query, start, count):
        qs = self.model_cls.objects.all()

        try:
            q = self.__class__.parser_getter().search(query, request)
        except (ValueError, SCIMParserError) as e:
            raise scim_exceptions.BadRequestError(
                "Invalid filter/search query: " + str(e)
            )
        else:
            qs = qs.filter(q)

        extra_filter_kwargs = self.get_extra_filter_kwargs(request)
        qs = qs.filter(**extra_filter_kwargs)

        extra_exclude_kwargs = self.get_extra_exclude_kwargs(request)
        qs = qs.exclude(**extra_exclude_kwargs)

        qs = self.get_queryset_post_processor(request, qs)
        qs = qs.order_by(self.lookup_field)

        return self._build_response(request, qs, *self._page(request))

class UsersView(CustomFilterMixin, views.UsersView):
    pass

class GroupsView(CustomFilterMixin, views.GroupsView):
    pass

I hope that this can be of use and If you have any more question, please let me know.