fix(db): resolve get_by_tags shadowing causing AttributeError

Rename the loop variable so an empty get_nodes() result does not
overwrite the DB node used in the fatal error path. Add regression test.

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: northdpole

application/database/db.py

@@ -1175,23 +1175,23 @@ def get_by_tags(self, tags: List[str]) -> List[cre_defs.Document]:
             cre_where_clause.append(sqla.and_(CRE.tags.like("%{}%".format(tag))))
 
         nodes = Node.query.filter(*nodes_where_clause).all() or []
-        for node in nodes:
-            node = self.get_nodes(
-                name=node.name,
-                section=node.section,
-                subsection=node.subsection,
-                version=node.version,
-                link=node.link,
-                ntype=node.ntype,
-                sectionID=node.section_id,
+        for db_node in nodes:
+            resolved = self.get_nodes(
+                name=db_node.name,
+                section=db_node.section,
+                subsection=db_node.subsection,
+                version=db_node.version,
+                link=db_node.link,
+                ntype=db_node.ntype,
+                sectionID=db_node.section_id,
             )
-            if node:
-                documents.extend(node)
+            if resolved:
+                documents.extend(resolved)
             else:
                 logger.fatal(
-                    "db.get_node returned None for"
+                    "db.get_node returned None for "
                     "Node %s:%s:%s that exists, BUG!"
-                    % (node.name, node.section, node.section_id)
+                    % (db_node.name, db_node.section, db_node.section_id)
                 )
 
         cres = CRE.query.filter(*cre_where_clause).all() or []

application/tests/db_test.py

@@ -125,6 +125,26 @@ def test_get_by_tags(self) -> None:
         self.assertEqual(self.collection.get_by_tags([]), [])
         self.assertEqual(self.collection.get_by_tags(["this should not be a tag"]), [])
 
+    @patch("application.database.db.logger")
+    def test_get_by_tags_empty_nodes_regression(self, mock_logger) -> None:
+        """
+        Simulate get_nodes returning an empty list to test the error path in get_by_tags.
+        See PR #837 regression fix.
+        """
+        dbstandard = db.Node(
+            section="regression_section",
+            name="regression_name",
+            tags="regression_tag",
+            ntype=defs.Standard.__name__,
+        )
+        self.collection.session.add(dbstandard)
+        self.collection.session.commit()
+
+        with patch.object(self.collection, "get_nodes", return_value=[]):
+            res = self.collection.get_by_tags(["regression_tag"])
+            self.assertEqual(res, [])
+            mock_logger.fatal.assert_called_once()
+
     def test_get_standards_names(self) -> None:
         result = self.collection.get_node_names()
         expected = [("Standard", "BarStand"), ("Standard", "Unlinked")]