fix: Backfill not_applicable on Item Tax Template Details for Germa…

…n companies (backport #54682) (#54686)

Co-authored-by: Raffael Meyer <14891507+barredterra@users.noreply.github.com>
fix: Backfill `not_applicable` on Item Tax Template Details for German companies (#54682)

erpnext/patches.txt

@@ -480,3 +480,4 @@ erpnext.patches.v16_0.set_root_type_in_account_categories
 erpnext.patches.v16_0.scr_inv_dimension
 erpnext.patches.v16_0.packed_item_inv_dimen
 erpnext.patches.v16_0.fix_titles
+erpnext.patches.v16_0.set_not_applicable_on_german_item_tax_templates

erpnext/patches/v16_0/set_not_applicable_on_german_item_tax_templates.py

@@ -0,0 +1,218 @@
+import frappe
+
+# Snapshot of the relevant German defaults when this migration was written.
+# Migration patches must not read mutable setup data, otherwise future edits to
+# country_wise_tax.json would change what this patch does on sites that have not
+# run it yet.
+#
+# For numbered charts, compare account_number + root_type because Account.account_name
+# is not unique within a company.
+SKR04_NOT_APPLICABLE_7_PERCENT_ACCOUNT_IDS = frozenset(
+	{
+		("3801", "Liability"),
+		("3802", "Liability"),
+		("3835", "Liability"),
+		("1401", "Asset"),
+		("1402", "Asset"),
+		("1541", "Asset"),
+	}
+)
+
+SKR04_NOT_APPLICABLE_19_PERCENT_ACCOUNT_IDS = frozenset(
+	{
+		("3806", "Liability"),
+		("3804", "Liability"),
+		("3837", "Liability"),
+		("1406", "Asset"),
+		("1404", "Asset"),
+		("1540", "Asset"),
+	}
+)
+
+SKR03_NOT_APPLICABLE_7_PERCENT_ACCOUNT_IDS = frozenset(
+	{
+		("1771", "Liability"),
+		("1772", "Liability"),
+		("1785", "Liability"),
+		("1571", "Asset"),
+		("1572", "Asset"),
+		("1541", "Asset"),
+	}
+)
+
+SKR03_NOT_APPLICABLE_19_PERCENT_ACCOUNT_IDS = frozenset(
+	{
+		("1776", "Liability"),
+		("1774", "Liability"),
+		("1787", "Liability"),
+		("1576", "Asset"),
+		("1574", "Asset"),
+		("1540", "Asset"),
+	}
+)
+
+STANDARD_NOT_APPLICABLE_7_PERCENT_ACCOUNT_LABELS = frozenset(
+	{
+		("Umsatzsteuer 7 %", "Liability"),
+		("Umsatzsteuer aus innergemeinschaftlichem Erwerb", "Liability"),
+		("Umsatzsteuer nach § 13b UStG", "Liability"),
+		("Abziehbare Vorsteuer 7 %", "Asset"),
+		("Abziehbare Vorsteuer aus innergemeinschaftlichem Erwerb", "Asset"),
+		("Abziehbare Vorsteuer nach § 13b UStG", "Asset"),
+	}
+)
+
+STANDARD_NOT_APPLICABLE_19_PERCENT_ACCOUNT_LABELS = frozenset(
+	{
+		("Umsatzsteuer 19 %", "Liability"),
+		("Umsatzsteuer aus innergemeinschaftlichem Erwerb 19 %", "Liability"),
+		("Umsatzsteuer nach § 13b UStG 19 %", "Liability"),
+		("Abziehbare Vorsteuer 19 %", "Asset"),
+		("Abziehbare Vorsteuer aus innergemeinschaftlichem Erwerb 19 %", "Asset"),
+		("Abziehbare Vorsteuer nach § 13b UStG 19 %", "Asset"),
+	}
+)
+
+STANDARD_WITH_NUMBERS_NOT_APPLICABLE_7_PERCENT_ACCOUNT_IDS = frozenset(
+	{
+		("2321", "Liability"),
+		("2331", "Liability"),
+		("2341", "Liability"),
+		("1521", "Asset"),
+		("1531", "Asset"),
+		("1541", "Asset"),
+	}
+)
+
+STANDARD_WITH_NUMBERS_NOT_APPLICABLE_19_PERCENT_ACCOUNT_IDS = frozenset(
+	{
+		("2320", "Liability"),
+		("2330", "Liability"),
+		("2340", "Liability"),
+		("1520", "Asset"),
+		("1530", "Asset"),
+		("1540", "Asset"),
+	}
+)
+
+GERMAN_ITEM_TAX_TEMPLATE_NOT_APPLICABLE_ACCOUNTS = {
+	"SKR03 mit Kontonummern": {
+		"identifier_field": "account_number",
+		"templates": {
+			"19 %": SKR03_NOT_APPLICABLE_7_PERCENT_ACCOUNT_IDS,
+			"7 %": SKR03_NOT_APPLICABLE_19_PERCENT_ACCOUNT_IDS,
+			"0 %": SKR03_NOT_APPLICABLE_7_PERCENT_ACCOUNT_IDS
+			| SKR03_NOT_APPLICABLE_19_PERCENT_ACCOUNT_IDS
+			| frozenset({("1588", "Asset")}),
+		},
+	},
+	"SKR04 mit Kontonummern": {
+		"identifier_field": "account_number",
+		"templates": {
+			"19 %": SKR04_NOT_APPLICABLE_7_PERCENT_ACCOUNT_IDS,
+			"7 %": SKR04_NOT_APPLICABLE_19_PERCENT_ACCOUNT_IDS,
+			"0 %": SKR04_NOT_APPLICABLE_7_PERCENT_ACCOUNT_IDS
+			| SKR04_NOT_APPLICABLE_19_PERCENT_ACCOUNT_IDS
+			| frozenset({("1433", "Asset")}),
+		},
+	},
+	"Standard": {
+		"identifier_field": "account_name",
+		"templates": {
+			"19 %": STANDARD_NOT_APPLICABLE_7_PERCENT_ACCOUNT_LABELS,
+			"7 %": STANDARD_NOT_APPLICABLE_19_PERCENT_ACCOUNT_LABELS,
+			"0%": STANDARD_NOT_APPLICABLE_7_PERCENT_ACCOUNT_LABELS
+			| STANDARD_NOT_APPLICABLE_19_PERCENT_ACCOUNT_LABELS
+			| frozenset({("Entstandene Einfuhrumsatzsteuer", "Asset")}),
+		},
+	},
+	"Standard with Numbers": {
+		"identifier_field": "account_number",
+		"templates": {
+			"19%": STANDARD_WITH_NUMBERS_NOT_APPLICABLE_7_PERCENT_ACCOUNT_IDS,
+			"7%": STANDARD_WITH_NUMBERS_NOT_APPLICABLE_19_PERCENT_ACCOUNT_IDS,
+			"0 %": STANDARD_WITH_NUMBERS_NOT_APPLICABLE_7_PERCENT_ACCOUNT_IDS
+			| STANDARD_WITH_NUMBERS_NOT_APPLICABLE_19_PERCENT_ACCOUNT_IDS
+			| frozenset({("1550", "Asset")}),
+		},
+	},
+}
+
+
+def update_account_cache(accounts, account_cache):
+	missing_accounts = set(accounts) - set(account_cache)
+	if not missing_accounts:
+		return
+
+	for account in frappe.get_all(
+		"Account",
+		filters={"name": ("in", tuple(sorted(missing_accounts)))},
+		fields=["name", "account_name", "account_number", "root_type"],
+	):
+		account_cache[account.name] = account
+
+
+def get_account_identifier(account, identifier_field, account_cache):
+	cached_account = account_cache.get(account)
+	if not cached_account:
+		return None
+
+	return cached_account.get(identifier_field), cached_account.root_type
+
+
+def execute():
+	"""Backfill `not_applicable` on Item Tax Template Details for German companies.
+
+	Before the `not_applicable` flag existed, German default templates used
+	`tax_rate: 0` to mean "this tax does not apply to the item" (as opposed to
+	an explicit 0% rate). For each German company, this patch looks up the
+	historical defaults for its Chart of Accounts and sets
+	`not_applicable = 1` on detail rows that still match those defaults
+	(same template title, same zero-rate tax account identifier set, flag still unset),
+	leaving any user-customised rows untouched.
+	"""
+	companies = frappe.get_all(
+		"Company",
+		filters={"country": "Germany"},
+		fields=["name", "chart_of_accounts"],
+	)
+	account_cache = {}
+
+	for company in companies:
+		chart = GERMAN_ITEM_TAX_TEMPLATE_NOT_APPLICABLE_ACCOUNTS.get(company.chart_of_accounts)
+		if not chart:
+			continue
+
+		identifier_field = chart["identifier_field"]
+		for template_title, target_accounts in chart["templates"].items():
+			itt_names = frappe.get_all(
+				"Item Tax Template",
+				filters={"company": company.name, "title": template_title},
+				pluck="name",
+			)
+			for itt_name in itt_names:
+				zero_rate_details = frappe.get_all(
+					"Item Tax Template Detail",
+					filters={"parent": itt_name, "tax_rate": 0},
+					fields=["name", "tax_type", "not_applicable"],
+				)
+				update_account_cache((d.tax_type for d in zero_rate_details), account_cache)
+				zero_rate_accounts_by_detail = {
+					d.name: get_account_identifier(d.tax_type, identifier_field, account_cache)
+					for d in zero_rate_details
+				}
+				if any(identifier is None for identifier in zero_rate_accounts_by_detail.values()):
+					continue
+
+				if set(zero_rate_accounts_by_detail.values()) != target_accounts:
+					continue
+
+				for d in zero_rate_details:
+					if not d.not_applicable:
+						frappe.db.set_value(
+							"Item Tax Template Detail",
+							d.name,
+							"not_applicable",
+							1,
+							update_modified=False,
+						)