feat(payment-entry): warn user before cancelling reconciled payment entry

(cherry picked from commit f0ba54d957)

erpnext/accounts/doctype/payment_entry/payment_entry.js

@@ -1726,6 +1726,35 @@ frappe.ui.form.on("Payment Entry", {
 			},
 		});
 	},
+
+	before_cancel: function (frm) {
+		return new Promise((resolve, reject) => {
+			frappe.call({
+				method: "erpnext.accounts.doctype.payment_entry.payment_entry.get_linked_bank_transactions",
+				args: { payment_entry: frm.doc.name },
+				callback: function (r) {
+					const linked = r.message || [];
+					if (!linked.length) {
+						resolve();
+						return;
+					}
+					const bt_links = linked
+						.map((name) => frappe.utils.get_form_link("Bank Transaction", name, true))
+						.join(", ");
+					frappe.confirm(
+						__(
+							"This Payment Entry is reconciled with {0}. Cancelling will automatically unreconcile it. Do you want to proceed?",
+							[bt_links]
+						),
+						() => resolve(),
+						() => reject(),
+						__("Yes"),
+						__("No")
+					);
+				},
+			});
+		});
+	},
 });
 
 frappe.ui.form.on("Payment Entry Reference", {

erpnext/accounts/doctype/payment_entry/payment_entry.py

@@ -3568,3 +3568,16 @@ def make_payment_order(source_name, target_doc=None):
 @erpnext.allow_regional
 def add_regional_gl_entries(gl_entries, doc):
 	return
+
+
+@frappe.whitelist()
+def get_linked_bank_transactions(payment_entry: str) -> list:
+	frappe.has_permission("Payment Entry", ptype="read", doc=payment_entry, throw=True)
+	return frappe.get_all(
+		"Bank Transaction Payments",
+		filters={
+			"payment_document": "Payment Entry",
+			"payment_entry": payment_entry,
+		},
+		pluck="parent",
+	)