add admin_filters tests to CI and fix bugs identified by them

.github/workflows/test-python.yml

@@ -51,6 +51,7 @@ jobs:
       - name: Run tests
         run: >
           python3 django_repo/tests/runtests.py --settings mongodb_settings -v 2
+          admin_filters
           aggregation
           aggregation_regress
           annotations

django_mongodb/aggregates.py

@@ -1,9 +1,6 @@
-from copy import deepcopy
-
 from django.db.models.aggregates import Aggregate, Count, StdDev, Variance
 from django.db.models.expressions import Case, Value, When
 from django.db.models.lookups import IsNull
-from django.db.models.sql.where import WhereNode
 
 from .query_utils import process_lhs
 
@@ -45,12 +42,9 @@ def count(self, compiler, connection, resolve_inner_expression=False, **extra_co
             node = self.copy()
             node.filter = None
             source_expressions = node.get_source_expressions()
-            filter_ = deepcopy(self.filter)
-            filter_.add(
-                WhereNode([IsNull(source_expressions[0], True)], negated=True),
-                filter_.default,
+            condition = When(
+                self.filter, then=Case(When(IsNull(source_expressions[0], False), then=Value(1)))
             )
-            condition = When(filter_, then=Value(1))
             node.set_source_expressions([Case(condition)] + source_expressions[1:])
             inner_expression = process_lhs(node, compiler, connection)
         else:

django_mongodb/compiler.py

@@ -368,8 +368,12 @@ def build_query(self, columns=None):
                 )
                 if not query.aggregation_pipeline:
                     query.aggregation_pipeline = []
-                query.aggregation_pipeline.append({"$group": {"_id": distinct_fields}})
-                query.project_fields = {key: f"$_id.{key}" for key in distinct_fields}
+                query.aggregation_pipeline.extend(
+                    [
+                        {"$group": {"_id": distinct_fields}},
+                        {"$project": {key: f"$_id.{key}" for key in distinct_fields}},
+                    ]
+                )
             else:
                 # Otherwise, project fields without grouping.
                 query.project_fields = self.get_project_fields(columns, ordering_fields)

django_mongodb/query.py

@@ -154,7 +154,7 @@ def join(self, compiler, connection):
                 if isinstance(hand_side_value, Col):
                     # If the column is not part of the joined table, add it to
                     # lhs_fields.
-                    if hand_side_value.alias != self.table_name:
+                    if hand_side_value.alias != self.table_alias:
                         pos = len(lhs_fields)
                         lhs_fields.append(expr.lhs.as_mql(compiler, connection))
                     else: