refactor(sales_invoice): simplify fixed-asset and inter-company validations

validate_fixed_asset (C/11) is flattened with a guard clause and the per-item
checks move into _validate_fixed_asset_item. validate_inter_company_party
(C/12) splits into _get_inter_company_party_config plus _validate_against_reference
and _validate_internal_party_company (conditions preserved verbatim). No C-rank
function remains in either module.

Characterize the previously-untested asset-sale throws (missing asset, update
stock, return without return-against, selling a sold/scrapped asset) and the
asset-restore note text before the move; behaviour is unchanged (asset and
inter-company suites green).

erpnext/accounts/doctype/sales_invoice/services/fixed_assets.py

@@ -25,30 +25,35 @@ class FixedAssetService:
 		if doc.doctype != "Sales Invoice":
 			return
 
-		for d in doc.get("items"):
-			if not d.is_fixed_asset:
-				continue
+		for item in doc.get("items"):
+			if item.is_fixed_asset:
+				self._validate_fixed_asset_item(item)
 
-			if d.asset:
-				if not doc.is_return:
-					asset_status = frappe.db.get_value("Asset", d.asset, "status")
-					if doc.update_stock:
-						frappe.throw(_("'Update Stock' cannot be checked for fixed asset sale"))
-					elif asset_status in ("Scrapped", "Cancelled", "Capitalized"):
-						frappe.throw(
-							_("Row #{0}: Asset {1} cannot be sold, it is already {2}").format(
-								d.idx, d.asset, asset_status
-							)
-						)
-					elif asset_status == "Sold" and not doc.is_return:
-						frappe.throw(_("Row #{0}: Asset {1} is already sold").format(d.idx, d.asset))
-				elif not doc.return_against:
-					frappe.throw(_("Row #{0}: Return Against is required for returning asset").format(d.idx))
-			else:
-				frappe.throw(
-					_("Row #{0}: You must select an Asset for Item {1}.").format(d.idx, d.item_code),
-					title=_("Missing Asset"),
+	def _validate_fixed_asset_item(self, item) -> None:
+		doc = self.doc
+		if not item.asset:
+			frappe.throw(
+				_("Row #{0}: You must select an Asset for Item {1}.").format(item.idx, item.item_code),
+				title=_("Missing Asset"),
+			)
+
+		if doc.is_return:
+			if not doc.return_against:
+				frappe.throw(_("Row #{0}: Return Against is required for returning asset").format(item.idx))
+			return
+
+		if doc.update_stock:
+			frappe.throw(_("'Update Stock' cannot be checked for fixed asset sale"))
+
+		asset_status = frappe.db.get_value("Asset", item.asset, "status")
+		if asset_status in ("Scrapped", "Cancelled", "Capitalized"):
+			frappe.throw(
+				_("Row #{0}: Asset {1} cannot be sold, it is already {2}").format(
+					item.idx, item.asset, asset_status
 				)
+			)
+		if asset_status == "Sold":
+			frappe.throw(_("Row #{0}: Asset {1} is already sold").format(item.idx, item.asset))
 
 	def set_income_account_for_fixed_assets(self) -> None:
 		for item in self.doc.items:

erpnext/accounts/doctype/sales_invoice/services/inter_company.py

@@ -13,36 +13,54 @@ def validate_inter_company_party(
 	if not party:
 		return
 
-	if doctype in ["Sales Invoice", "Sales Order"]:
-		partytype, ref_partytype, internal = "Customer", "Supplier", "is_internal_customer"
-		ref_doc = "Purchase Invoice" if doctype == "Sales Invoice" else "Purchase Order"
-	else:
-		partytype, ref_partytype, internal = "Supplier", "Customer", "is_internal_supplier"
-		ref_doc = "Sales Invoice" if doctype == "Purchase Invoice" else "Sales Order"
+	config = _get_inter_company_party_config(doctype)
 
 	if inter_company_reference:
-		doc = frappe.get_doc(ref_doc, inter_company_reference)
-		ref_party = doc.supplier if doctype in ["Sales Invoice", "Sales Order"] else doc.customer
-		if frappe.db.get_value(partytype, {"represents_company": doc.company}, "name") != party:
-			frappe.throw(_("Invalid {0} for Inter Company Transaction.").format(_(partytype)))
-		if frappe.get_cached_value(ref_partytype, ref_party, "represents_company") != company:
-			frappe.throw(_("Invalid Company for Inter Company Transaction."))
+		_validate_against_reference(config, party, company, inter_company_reference)
+	elif frappe.db.get_value(config.partytype, {"name": party, config.internal: 1}, "name") == party:
+		_validate_internal_party_company(config.partytype, party, company)
 
-	elif frappe.db.get_value(partytype, {"name": party, internal: 1}, "name") == party:
-		companies = [
-			d.company
-			for d in frappe.get_all(
-				"Allowed To Transact With",
-				fields=["company"],
-				filters={"parenttype": partytype, "parent": party},
-			)
-		]
-		if company not in companies:
-			frappe.throw(
-				_(
-					"{0} not allowed to transact with {1}. Please change the Company or add the Company in the 'Allowed To Transact With'-Section in the Customer record."
-				).format(_(partytype), company)
-			)
+
+def _get_inter_company_party_config(doctype: str) -> "frappe._dict":
+	if doctype in ["Sales Invoice", "Sales Order"]:
+		return frappe._dict(
+			partytype="Customer",
+			ref_partytype="Supplier",
+			internal="is_internal_customer",
+			ref_doc="Purchase Invoice" if doctype == "Sales Invoice" else "Purchase Order",
+		)
+	return frappe._dict(
+		partytype="Supplier",
+		ref_partytype="Customer",
+		internal="is_internal_supplier",
+		ref_doc="Sales Invoice" if doctype == "Purchase Invoice" else "Sales Order",
+	)
+
+
+def _validate_against_reference(config, party: str, company: str, inter_company_reference: str) -> None:
+	doc = frappe.get_doc(config.ref_doc, inter_company_reference)
+	ref_party = doc.supplier if config.partytype == "Customer" else doc.customer
+	if frappe.db.get_value(config.partytype, {"represents_company": doc.company}, "name") != party:
+		frappe.throw(_("Invalid {0} for Inter Company Transaction.").format(_(config.partytype)))
+	if frappe.get_cached_value(config.ref_partytype, ref_party, "represents_company") != company:
+		frappe.throw(_("Invalid Company for Inter Company Transaction."))
+
+
+def _validate_internal_party_company(partytype: str, party: str, company: str) -> None:
+	companies = [
+		d.company
+		for d in frappe.get_all(
+			"Allowed To Transact With",
+			fields=["company"],
+			filters={"parenttype": partytype, "parent": party},
+		)
+	]
+	if company not in companies:
+		frappe.throw(
+			_(
+				"{0} not allowed to transact with {1}. Please change the Company or add the Company in the 'Allowed To Transact With'-Section in the Customer record."
+			).format(_(partytype), company)
+		)
 
 
 def update_linked_doc(doctype: str, name: str, inter_company_reference: str | None) -> None:

erpnext/accounts/doctype/sales_invoice/test_sales_invoice.py

@@ -3667,6 +3667,49 @@ class TestSalesInvoice(ERPNextTestSuite):
 			self.assertEqual(expected_values[i][2], schedule.accumulated_depreciation_amount)
 			self.assertTrue(schedule.journal_entry)
 
+	def test_fixed_asset_sale_validations(self):
+		from erpnext.accounts.doctype.sales_invoice.services.fixed_assets import FixedAssetService
+
+		asset = create_asset(item_code="Macbook Pro", calculate_depreciation=0, submit=1)
+
+		def asset_invoice(asset_name, **kwargs):
+			si = create_sales_invoice(
+				item_code="Macbook Pro", asset=asset_name, qty=1, rate=90000, do_not_save=True, **kwargs
+			)
+			si.items[0].is_fixed_asset = 1
+			return si
+
+		with self.subTest("item without an asset is rejected"):
+			si = asset_invoice(None)
+			self.assertRaises(frappe.ValidationError, FixedAssetService(si).validate_fixed_asset)
+
+		with self.subTest("update stock on an asset sale is rejected"):
+			si = asset_invoice(asset.name, update_stock=1)
+			self.assertRaises(frappe.ValidationError, FixedAssetService(si).validate_fixed_asset)
+
+		with self.subTest("return without return-against is rejected"):
+			si = asset_invoice(asset.name, is_return=1)
+			self.assertRaises(frappe.ValidationError, FixedAssetService(si).validate_fixed_asset)
+
+		for bad_status in ("Sold", "Scrapped", "Cancelled", "Capitalized"):
+			with self.subTest(f"selling a {bad_status} asset is rejected"):
+				frappe.db.set_value("Asset", asset.name, "status", bad_status)
+				si = asset_invoice(asset.name)
+				self.assertRaises(frappe.ValidationError, FixedAssetService(si).validate_fixed_asset)
+				frappe.db.set_value("Asset", asset.name, "status", "Submitted")
+
+	def test_fixed_asset_restore_note_text(self):
+		from erpnext.accounts.doctype.sales_invoice.services.fixed_assets import FixedAssetService
+
+		asset = frappe._dict(doctype="Asset", name="_Test Asset For Note")
+		si = create_sales_invoice(do_not_save=True)
+
+		si.is_return = 1
+		self.assertIn("returned", FixedAssetService(si)._get_note_for_asset_return(asset))
+
+		si.is_return = 0
+		self.assertIn("restored", FixedAssetService(si)._get_note_for_asset_return(asset))
+
 	def test_sales_invoice_against_supplier(self):
 		from erpnext.accounts.doctype.opening_invoice_creation_tool.test_opening_invoice_creation_tool import (
 			make_customer,