fix: let Purchase Receipt cancel defer to Frappe's linked-document check (#57592)

on_cancel pre-blocked cancellation with its own "Purchase Invoice is
already submitted" guard, duplicating the check Frappe already runs for any
submitted linked document. Drop the guard and the unused check_next_docstatus()
method it mirrored so the receipt defers to the framework: the Cancel All
Documents flow cancels the invoice first and then the receipt, and a direct
cancel is still rejected by Frappe's linked-document check.

Add a regression test that a direct cancel of a receipt with a submitted
invoice is rejected and rolls back, leaving no stray stock or GL entries.

erpnext/stock/doctype/purchase_receipt/purchase_receipt.py

@@ -423,31 +423,10 @@ class PurchaseReceipt(BuyingController):
 						row.received_qty,
 					)
 
-	def check_next_docstatus(self):
-		submit_rv = frappe.get_all(
-			"Purchase Invoice Item",
-			filters={"purchase_receipt": self.name, "docstatus": 1},
-			fields=["parent"],
-			as_list=True,
-			limit=1,
-		)
-		if submit_rv:
-			frappe.throw(_("Purchase Invoice {0} is already submitted").format(submit_rv[0][0]))
-
 	def on_cancel(self):
 		super().on_cancel()
 
 		self.check_for_on_hold_or_closed_status("Purchase Order", "purchase_order")
-		# Check if Purchase Invoice has been submitted against current Purchase Order
-		submitted = frappe.get_all(
-			"Purchase Invoice Item",
-			filters={"purchase_receipt": self.name, "docstatus": 1},
-			fields=["parent"],
-			as_list=True,
-			limit=1,
-		)
-		if submitted:
-			frappe.throw(_("Purchase Invoice {0} is already submitted").format(submitted[0][0]))
 
 		self.update_prevdoc_status()
 		self.update_billing_status()

erpnext/stock/doctype/purchase_receipt/test_purchase_receipt.py

@@ -6131,17 +6131,31 @@ class TestPurchaseReceipt(ERPNextTestSuite):
 		# already received against this PO line, excluding pr2 itself, is pr1's 4
 		self.assertEqual(pr2.get_already_received_qty(po.name, po_detail), 4.0)
 
-	def test_check_next_docstatus_blocks_with_submitted_invoice(self):
-		"""check_next_docstatus must flag a submitted Purchase Invoice drawn from the receipt —
-		covers the converted child-table get_all (Purchase Invoice Item, docstatus=1)."""
+	def test_cancel_blocked_by_submitted_invoice_rolls_back(self):
+		"""A submitted Purchase Invoice must block cancelling its Purchase Receipt. Frappe's backlink
+		check rejects the cancel only after on_cancel has run stock, GL, and status work, so the whole
+		transaction has to roll back: the receipt stays submitted with no leaked ledger entries."""
 		pr = make_purchase_receipt()
 		pi = make_purchase_invoice(pr.name)
 		pi.insert()
 		pi.submit()
 
-		with self.assertRaises(frappe.ValidationError) as cm:
-			pr.check_next_docstatus()
-		self.assertIn("is already submitted", str(cm.exception))
+		pr.reload()
+		status_before = pr.status
+		sle_before = frappe.db.count("Stock Ledger Entry", {"voucher_no": pr.name})
+		gle_before = frappe.db.count("GL Entry", {"voucher_no": pr.name})
+
+		frappe.db.savepoint("before_blocked_cancel")
+		with self.assertRaises(frappe.LinkExistsError) as cm:
+			pr.cancel()
+		self.assertIn(pi.name, str(cm.exception))
+		frappe.db.rollback(save_point="before_blocked_cancel")  # mimic the request-level rollback
+
+		pr.reload()
+		self.assertEqual(pr.docstatus, 1)
+		self.assertEqual(pr.status, status_before)
+		self.assertEqual(frappe.db.count("Stock Ledger Entry", {"voucher_no": pr.name}), sle_before)
+		self.assertEqual(frappe.db.count("GL Entry", {"voucher_no": pr.name}), gle_before)
 
 
 def create_asset_category_for_pr_test():