feat: validate purchase receipt exchange rate parity on purchase invoice (backport #58177) (#58189)

* feat: validate purchase receipt exchange rate parity on purchase invoice (#58177)

(cherry picked from commit 70a8a2d0c5)

# Conflicts:
#	erpnext/accounts/doctype/purchase_invoice/test_purchase_invoice.py

* chore: fix conflicts

Removed assertion for exchange rate discrepancy in purchase invoice test.

* test: fix backport of exchange rate difference test for non stock item

The conflict resolution left behind stale amount/discrepancy lookups
referencing a removed second item row (IndexError in CI and F841 ruff
failures). Align the test with the develop version: single non stock
item, PR at 80 / PI at 70, and assert no exchange gain/loss GL entry.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

---------

Co-authored-by: rohitwaghchaure <rohitw1991@gmail.com>
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

erpnext/accounts/doctype/purchase_invoice/purchase_invoice.py

@@ -291,6 +291,7 @@ class PurchaseInvoice(BuyingController):
 		self.validate_multiple_billing("Purchase Receipt", "pr_detail", "amount")
 		self.set_status()
 		self.validate_purchase_receipt_if_update_stock()
+		self.validate_exchange_rate_with_purchase_receipt()
 		validate_inter_company_party(
 			self.doctype, self.supplier, self.company, self.inter_company_invoice_reference
 		)
@@ -313,6 +314,47 @@ class PurchaseInvoice(BuyingController):
 		if total_billed_qty and total_received_qty:
 			self.per_received = total_received_qty / total_billed_qty * 100
 
+	def validate_exchange_rate_with_purchase_receipt(self):
+		if self.is_internal_transfer() or not erpnext.is_perpetual_inventory_enabled(self.company):
+			return
+
+		stock_items = self.get_stock_items()
+		receipts = {
+			item.purchase_receipt
+			for item in self.items
+			if item.purchase_receipt and item.item_code in stock_items
+		}
+		if not receipts:
+			return
+
+		if frappe.db.get_single_value("Buying Settings", "set_landed_cost_based_on_purchase_invoice_rate"):
+			return
+
+		mismatched = [
+			f"{frappe.bold(row.name)} ({row.conversion_rate})"
+			for row in frappe.get_all(
+				"Purchase Receipt",
+				filters={"name": ("in", list(receipts))},
+				fields=["name", "currency", "conversion_rate"],
+			)
+			if row.currency == self.currency
+			and flt(row.conversion_rate)
+			and flt(row.conversion_rate) != flt(self.conversion_rate)
+		]
+		if not mismatched:
+			return
+
+		frappe.throw(
+			_(
+				"Exchange rate {0} does not match the exchange rate of Purchase Receipt {1}. Use the same exchange rate as the Purchase Receipt or enable {2} in {3} to adjust the landed cost based on this invoice."
+			).format(
+				frappe.bold(self.conversion_rate),
+				", ".join(mismatched),
+				frappe.bold(_("Set Landed Cost Based on Purchase Invoice Rate")),
+				get_link_to_form("Buying Settings", "Buying Settings", _("Buying Settings")),
+			)
+		)
+
 	def validate_invoice_hold(self):
 		if self.is_return:
 			frappe.throw(_("Return Purchase Invoice cannot be held."))

erpnext/accounts/doctype/purchase_invoice/test_purchase_invoice.py

@@ -513,6 +513,12 @@ class TestPurchaseInvoice(FrappeTestCase, StockTestMixin):
 		)
 
 		frappe.db.set_single_value("Buying Settings", "set_landed_cost_based_on_purchase_invoice_rate", 0)
+		self.addCleanup(
+			frappe.db.set_single_value,
+			"Buying Settings",
+			"set_landed_cost_based_on_purchase_invoice_rate",
+			original_value,
+		)
 
 		pr = make_purchase_receipt(
 			company="_Test Company with perpetual inventory",
@@ -524,25 +530,15 @@ class TestPurchaseInvoice(FrappeTestCase, StockTestMixin):
 		pi = create_purchase_invoice(pr.name)
 		pi.conversion_rate = 80
 
+		self.assertRaises(frappe.ValidationError, pi.insert)
+
+		pi.conversion_rate = 70
 		pi.insert()
 		pi.submit()
 
-		# Get exchnage gain and loss account
 		exchange_gain_loss_account = frappe.db.get_value("Company", pi.company, "exchange_gain_loss_account")
-
-		# fetching the latest GL Entry with exchange gain and loss account account
-		amount = frappe.db.get_value(
-			"GL Entry", {"account": exchange_gain_loss_account, "voucher_no": pi.name}, "debit"
-		)
-
-		discrepancy_caused_by_exchange_rate_diff = abs(
-			pi.items[0].base_net_amount - pr.items[0].base_net_amount
-		)
-
-		self.assertEqual(discrepancy_caused_by_exchange_rate_diff, amount)
-
-		frappe.db.set_single_value(
-			"Buying Settings", "set_landed_cost_based_on_purchase_invoice_rate", original_value
+		self.assertFalse(
+			frappe.db.exists("GL Entry", {"account": exchange_gain_loss_account, "voucher_no": pi.name})
 		)
 
 	def test_purchase_invoice_with_exchange_rate_difference_for_non_stock_item(self):
@@ -550,11 +546,21 @@ class TestPurchaseInvoice(FrappeTestCase, StockTestMixin):
 			make_purchase_invoice as create_purchase_invoice,
 		)
 
-		# Creating Purchase Invoice with USD currency
+		original_value = frappe.db.get_single_value(
+			"Buying Settings", "set_landed_cost_based_on_purchase_invoice_rate"
+		)
+		frappe.db.set_single_value("Buying Settings", "set_landed_cost_based_on_purchase_invoice_rate", 0)
+		self.addCleanup(
+			frappe.db.set_single_value,
+			"Buying Settings",
+			"set_landed_cost_based_on_purchase_invoice_rate",
+			original_value,
+		)
+
 		pr = frappe.new_doc("Purchase Receipt")
 		pr.currency = "USD"
 		pr.company = "_Test Company with perpetual inventory"
-		pr.conversion_rate = (70,)
+		pr.conversion_rate = 80
 		pr.supplier = "_Test Supplier USD"
 		pr.append(
 			"items",
@@ -564,34 +570,20 @@ class TestPurchaseInvoice(FrappeTestCase, StockTestMixin):
 				"rate": 100,
 			},
 		)
-		pr.append(
-			"items",
-			{"item_code": "_Test Item", "qty": 1, "rate": 5, "warehouse": "Stores - TCP1"},
-		)
 		pr.insert()
 		pr.submit()
 
-		# Createing purchase invoice against Purchase Receipt
 		pi = create_purchase_invoice(pr.name)
-		pi.conversion_rate = 80
+		pi.conversion_rate = 70
 		pi.credit_to = "_Test Payable USD - TCP1"
 		pi.insert()
 		pi.submit()
 
-		# Get exchnage gain and loss account
 		exchange_gain_loss_account = frappe.db.get_value("Company", pi.company, "exchange_gain_loss_account")
-
-		# fetching the latest GL Entry with exchange gain and loss account account
-		amount = frappe.db.get_value(
-			"GL Entry", {"account": exchange_gain_loss_account, "voucher_no": pi.name}, "debit"
+		self.assertFalse(
+			frappe.db.exists("GL Entry", {"account": exchange_gain_loss_account, "voucher_no": pi.name})
 		)
 
-		discrepancy_caused_by_exchange_rate_diff = abs(
-			pi.items[1].base_net_amount - pr.items[1].base_net_amount
-		)
-
-		self.assertEqual(discrepancy_caused_by_exchange_rate_diff, amount)
-
 	def test_purchase_invoice_change_naming_series(self):
 		pi = frappe.copy_doc(test_records[1])
 		pi.insert()