fix(postgres): use portable GroupConcat in Lost Opportunity report

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

erpnext/crm/report/lost_opportunity/lost_opportunity.py

@@ -5,8 +5,7 @@
 import frappe
 from frappe import _
 from frappe.query_builder import DocType
-from frappe.query_builder.custom import GROUP_CONCAT
+from frappe.query_builder.functions import Date, GroupConcat
-from frappe.query_builder.functions import Date
 
 Opportunity = DocType("Opportunity")
 OpportunityLostReasonDetail = DocType("Opportunity Lost Reason Detail")
@@ -72,6 +71,9 @@ def get_columns():
 
 
 def get_data(filters):
+	# db-aware GROUP_CONCAT (MariaDB) / STRING_AGG (postgres) with a ", " separator
+	lost_reasons = GroupConcat(OpportunityLostReasonDetail.lost_reason, ", ", alias="lost_reason")
+
 	query = (
 		frappe.qb.from_(Opportunity)
 		.left_join(OpportunityLostReasonDetail)
@@ -85,7 +87,7 @@ def get_data(filters):
 			Opportunity.party_name,
 			Opportunity.customer_name,
 			Opportunity.opportunity_type,
-			GROUP_CONCAT(OpportunityLostReasonDetail.lost_reason, alias="lost_reason").separator(", "),
+			lost_reasons,
 			Opportunity.sales_stage,
 			Opportunity.territory,
 		)

erpnext/crm/report/lost_opportunity/test_lost_opportunity.py

@@ -0,0 +1,22 @@
+# Copyright (c) 2024, Frappe Technologies Pvt. Ltd. and contributors
+# For license information, please see license.txt
+
+import frappe
+from frappe.utils import add_days, today
+
+from erpnext.crm.report.lost_opportunity.lost_opportunity import execute
+from erpnext.tests.utils import ERPNextTestSuite
+
+
+class TestLostOpportunity(ERPNextTestSuite):
+	def test_report_aggregates_lost_reasons(self):
+		# Exercises the db-aware GROUP_CONCAT (MariaDB) / STRING_AGG (postgres) aggregation of the
+		# child "Opportunity Lost Reason Detail" rows. The MySQL-only GROUP_CONCAT term would fail to
+		# compile on postgres, so simply running the report query guards the portability fix on both
+		# databases.
+		company = frappe.db.get_value("Company", {}, "name")
+		columns, data = execute(
+			frappe._dict({"company": company, "from_date": add_days(today(), -365), "to_date": today()})
+		)
+		self.assertTrue(columns)
+		self.assertIsInstance(data, list)