Merge branch 'develop' into gst_invoice_validation
diff --git a/erpnext/hooks.py b/erpnext/hooks.py
index 59639ff..f87769c 100644
--- a/erpnext/hooks.py
+++ b/erpnext/hooks.py
@@ -278,6 +278,9 @@
 	('Sales Invoice', 'Sales Order', 'Delivery Note', 'Purchase Invoice', 'Purchase Order', 'Purchase Receipt'): {
 		'validate': ['erpnext.regional.india.utils.set_place_of_supply']
 	},
+	('Sales Invoice', 'Purchase Invoice'): {
+		'validate': ['erpnext.regional.india.utils.validate_document_name']
+	},
 	"Contact": {
 		"on_trash": "erpnext.support.doctype.issue.issue.update_issue",
 		"after_insert": "erpnext.telephony.doctype.call_log.call_log.link_existing_conversations",
diff --git a/erpnext/regional/india/test_utils.py b/erpnext/regional/india/test_utils.py
new file mode 100644
index 0000000..7ce27f6
--- /dev/null
+++ b/erpnext/regional/india/test_utils.py
@@ -0,0 +1,38 @@
+from __future__ import unicode_literals
+
+import unittest
+import frappe
+from unittest.mock import patch
+from erpnext.regional.india.utils import validate_document_name
+
+
+class TestIndiaUtils(unittest.TestCase):
+	@patch("frappe.get_cached_value")
+	def test_validate_document_name(self, mock_get_cached):
+		mock_get_cached.return_value = "India"  # mock country
+		posting_date = "2021-05-01"
+
+		invalid_names = [ "SI$1231", "012345678901234567", "SI 2020 05", 
+				"SI.2020.0001", "PI2021 - 001" ]
+		for name in invalid_names:
+			doc = frappe._dict(name=name, posting_date=posting_date)
+			self.assertRaises(frappe.ValidationError, validate_document_name, doc)
+
+		valid_names = [ "012345678901236", "SI/2020/0001", "SI/2020-0001",
+			"2020-PI-0001", "PI2020-0001" ]
+		for name in valid_names:
+			doc = frappe._dict(name=name, posting_date=posting_date)
+			try:
+				validate_document_name(doc)
+			except frappe.ValidationError:
+				self.fail("Valid name {} throwing error".format(name))
+
+	@patch("frappe.get_cached_value")
+	def test_validate_document_name_not_india(self, mock_get_cached):
+		mock_get_cached.return_value = "Not India"
+		doc = frappe._dict(name="SI$123", posting_date="2021-05-01")
+
+		try:
+			validate_document_name(doc)
+		except frappe.ValidationError:
+			self.fail("Regional validation related to India are being applied to other countries")
diff --git a/erpnext/regional/india/utils.py b/erpnext/regional/india/utils.py
index cb30605..7980d0b 100644
--- a/erpnext/regional/india/utils.py
+++ b/erpnext/regional/india/utils.py
@@ -2,7 +2,7 @@
 import frappe, re, json
 from frappe import _
 import erpnext
-from frappe.utils import cstr, flt, date_diff, nowdate, round_based_on_smallest_currency_fraction, money_in_words
+from frappe.utils import cstr, flt, date_diff, nowdate, round_based_on_smallest_currency_fraction, money_in_words, getdate
 from erpnext.regional.india import states, state_numbers
 from erpnext.controllers.taxes_and_totals import get_itemised_tax, get_itemised_taxable_amount
 from erpnext.controllers.accounts_controller import get_taxes_and_charges
@@ -148,6 +148,20 @@
 def set_place_of_supply(doc, method=None):
 	doc.place_of_supply = get_place_of_supply(doc, doc.doctype)
 
+def validate_document_name(doc, method=None):
+	"""Validate GST invoice number requirements."""
+	country = frappe.get_cached_value("Company", doc.company, "country")
+
+	if country != "India" or getdate(doc.posting_date) < getdate("2021-04-01"):
+		return
+
+	if len(doc.name) > 16:
+		frappe.throw(_("Maximum length of document number should be 16 characters as per GST rules. Please change the naming series."))
+
+	gst_doc_name_pattern = re.compile(r"^[a-zA-Z0-9\-/]+$")
+	if not gst_doc_name_pattern.match(doc.name):
+		frappe.throw(_("Document name should only contain alphanumeric values, dash(-) and slash(/) characters as per GST rules. Please change the naming series."))
+
 # don't remove this function it is used in tests
 def test_method():
 	'''test function'''