fix: validate party's existing transaction currency before merging

(cherry picked from commit f48b90c600)

erpnext/accounts/party.py

@@ -1056,3 +1056,21 @@ def add_party_account(party_type, party, company, account):
 
 def render_address(address, check_permissions=True):
 	return frappe.call(_render_address, address, check_permissions=check_permissions)
+
+
+def validate_party_currency_before_merging(party_type, old_party, new_party):
+	for company in frappe.get_all("Company"):
+		old_party_currency = get_party_gle_currency(party_type, old_party, company.name)
+		new_party_currency = get_party_gle_currency(party_type, new_party, company.name)
+
+		if old_party_currency and new_party_currency and old_party_currency != new_party_currency:
+			frappe.throw(
+				_(
+					"Cannot merge {0} '{1}' into '{2}' as both have existing accounting entries in different currencies for company '{3}'."
+				).format(
+					party_type,
+					old_party,
+					new_party,
+					company.name,
+				)
+			)

erpnext/buying/doctype/supplier/supplier.py

@@ -14,6 +14,7 @@ from frappe.model.naming import set_name_by_naming_series, set_name_from_naming_
 from erpnext.accounts.party import (
 	get_dashboard_info,
 	validate_party_accounts,
+	validate_party_currency_before_merging,
 )
 from erpnext.controllers.website_list_for_contact import add_role_for_portal_user
 from erpnext.utilities.transaction_base import TransactionBase
@@ -208,6 +209,10 @@ class Supplier(TransactionBase):
 
 		delete_contact_and_address("Supplier", self.name)
 
+	def before_rename(self, olddn, newdn, merge=False):
+		if merge:
+			validate_party_currency_before_merging("Supplier", olddn, newdn)
+
 	def after_rename(self, olddn, newdn, merge=False):
 		if frappe.defaults.get_global_default("supp_master_name") == "Supplier Name":
 			self.db_set("supplier_name", newdn)

erpnext/selling/doctype/customer/customer.py

@@ -18,7 +18,11 @@ from frappe.utils import cint, cstr, flt, get_formatted_email, today
 from frappe.utils.deprecations import deprecated
 from frappe.utils.user import get_users_with_role
 
-from erpnext.accounts.party import get_dashboard_info, validate_party_accounts
+from erpnext.accounts.party import (
+	get_dashboard_info,
+	validate_party_accounts,
+	validate_party_currency_before_merging,
+)
 from erpnext.controllers.website_list_for_contact import add_role_for_portal_user
 from erpnext.utilities.transaction_base import TransactionBase
 
@@ -367,6 +371,10 @@ class Customer(TransactionBase):
 		if self.lead_name:
 			frappe.db.sql("update `tabLead` set status='Interested' where name=%s", self.lead_name)
 
+	def before_rename(self, olddn, newdn, merge=False):
+		if merge:
+			validate_party_currency_before_merging("Customer", olddn, newdn)
+
 	def after_rename(self, olddn, newdn, merge=False):
 		if frappe.defaults.get_global_default("cust_master_name") == "Customer Name":
 			self.db_set("customer_name", newdn)