fix: tests and quality issues

openedx_tagging/core/tagging/models/utils.py

@@ -3,8 +3,7 @@
 """
 from django.db.models import Aggregate, CharField
 from django.db.models.expressions import Func
-from django.db import connection
-
+from django.db import connection as db_connection
 
 RESERVED_TAG_CHARS = [
     '\t',  # Used in the database to separate tag levels in the "lineage" field
@@ -36,7 +35,10 @@ def as_sqlite(self, compiler, connection, **extra_context):
         )
 
 
-class StringAgg(Aggregate):
+from django.db.models import Aggregate, CharField
+from django.db.models.expressions import Combinable
+
+class StringAgg(Aggregate, Combinable):
     """
     Aggregate function that collects the values of some column across all rows,
     and creates a string by concatenating those values, with a specified separator.
@@ -45,28 +47,27 @@ class StringAgg(Aggregate):
     """
     # Default function is for MySQL (GROUP_CONCAT)
     function = 'GROUP_CONCAT'
-    template = '%(function)s(%(distinct)s%(expressions)s SEPARATOR %(delimiter)s)'
+    template = '%(function)s(%(distinct)s%(expressions)s)'
 
     def __init__(self, expression, distinct=False, delimiter=',', **extra):
-
-        self.delimiter=delimiter
+        self.delimiter = delimiter
         # Handle the distinct option and output type
         distinct_str = 'DISTINCT ' if distinct else ''
 
+        extra.update(dict(
+            distinct=distinct_str,
+            output_field=CharField()
+        ))
+
         # Check the database backend (PostgreSQL, MySQL, or SQLite)
-        if 'postgresql' in connection.vendor.lower():
+        if 'postgresql' in db_connection.vendor.lower():
             self.function = 'STRING_AGG'
             self.template = '%(function)s(%(distinct)s%(expressions)s, %(delimiter)s)'
-        elif 'mysql' in connection.vendor.lower() or 'sqlite' in connection.vendor.lower():
-            self.function = 'GROUP_CONCAT'
-            self.template = '%(function)s(%(distinct)s%(expressions)s SEPARATOR %(delimiter)s)'
+            extra.update({"delimiter": delimiter})
 
         # Initialize the parent class with the necessary parameters
         super().__init__(
             expression,
-            distinct=distinct_str,
-            delimiter=delimiter,
-            output_field=CharField(),
             **extra,
         )
 
@@ -80,3 +81,13 @@ def as_sql(self, compiler, connection, **extra_context):
         else:
             # MySQL/SQLite handles GROUP_CONCAT with SEPARATOR
             return super().as_sql(compiler, connection, **extra_context)
+
+    # Implementing abstract methods from Combinable
+    def __rand__(self, other):
+        return self._combine(other, 'AND', is_combinable=True)
+
+    def __ror__(self, other):
+        return self._combine(other, 'OR', is_combinable=True)
+
+    def __rxor__(self, other):
+        return self._combine(other, 'XOR', is_combinable=True)