feat: add consecutive calendar week (WW) for naming series

The calendar week is based on ISO 8601 but behaves slightly different
for the first and last days of a year to ensure consecutiveness:

* If the first days of a year would be in week 53 then 00 is used
  instead.
* if the last days of a year would be in week 01 then 53 is used
  instead.

Closes #14413

frappe/model/naming.py

@@ -175,6 +175,8 @@ def parse_naming_series(parts, doctype='', doc=''):
 			part = today.strftime("%d")
 		elif e == 'YYYY':
 			part = today.strftime('%Y')
+		elif e == 'WW':
+			part = determine_consecutive_week_number(today)
 		elif e == 'timestamp':
 			part = str(today)
 		elif e == 'FY':
@@ -193,6 +195,19 @@ def parse_naming_series(parts, doctype='', doc=''):
 	return n
 
 
+def determine_consecutive_week_number(datetime):
+	"""Determines the consecutive calendar week"""
+	m = datetime.month
+	# ISO 8601 calandar week
+	w = datetime.strftime('%V')
+	# Ensure consecutiveness for the first and last days of a year
+	if m == 1 and int(w) >= 52:
+		w = '00'
+	elif m == 12 and int(w) <= 1:
+		w = '53'
+	return w
+
+
 def getseries(key, digits):
 	# series created ?
 	# Using frappe.qb as frappe.get_values does not allow order_by=None

frappe/tests/test_naming.py

@@ -7,6 +7,7 @@ from frappe.utils import now_datetime
 
 from frappe.model.naming import getseries
 from frappe.model.naming import append_number_if_name_exists, revert_series_if_last
+from frappe.model.naming import determine_consecutive_week_number, parse_naming_series
 
 class TestNaming(unittest.TestCase):
 	def tearDown(self):
@@ -60,6 +61,34 @@ class TestNaming(unittest.TestCase):
 		self.assertEqual(todo.name, 'TODO-{month}-{status}-{series}'.format(
 			month=now_datetime().strftime('%m'), status=todo.status, series=series))
 
+	def test_format_autoname_for_consecutive_week_number(self):
+		'''
+		Test if braced params are replaced for consecutive week number in format autoname
+		'''
+		doctype = 'ToDo'
+
+		todo_doctype = frappe.get_doc('DocType', doctype)
+		todo_doctype.autoname = 'format:TODO-{WW}-{##}'
+		todo_doctype.save()
+
+		description = 'Format'
+
+		todo = frappe.new_doc(doctype)
+		todo.description = description
+		todo.insert()
+
+		series = getseries('', 2)
+
+		series = str(int(series)-1)
+
+		if len(series) < 2:
+			series = '0' + series
+
+		week = determine_consecutive_week_number(now_datetime())
+
+		self.assertEqual(todo.name, 'TODO-{week}-{series}'.format(
+			week=week, series=series))
+
 	def test_revert_series(self):
 		from datetime import datetime
 		year = datetime.now().year
@@ -150,3 +179,32 @@ class TestNaming(unittest.TestCase):
 		self.assertEqual(amended_doc.name, "{}-CANC-1".format(original_name))
 
 		submittable_doctype.delete()
+
+	def test_parse_naming_series_for_consecutive_week_number(self):
+		week = determine_consecutive_week_number(now_datetime())
+		name = parse_naming_series('PREFIX-.WW.-SUFFIX')
+		expected_name = 'PREFIX-{}-SUFFIX'.format(week)
+		self.assertEqual(name, expected_name)
+
+	def test_determine_consecutive_week_number(self):
+		from datetime import datetime
+
+		dt = datetime.fromisoformat("2019-12-31")
+		w = determine_consecutive_week_number(dt)
+		self.assertEqual(w, "53")
+
+		dt = datetime.fromisoformat("2020-01-01")
+		w = determine_consecutive_week_number(dt)
+		self.assertEqual(w, "01")
+
+		dt = datetime.fromisoformat("2020-01-15")
+		w = determine_consecutive_week_number(dt)
+		self.assertEqual(w, "03")
+
+		dt = datetime.fromisoformat("2021-01-01")
+		w = determine_consecutive_week_number(dt)
+		self.assertEqual(w, "00")
+
+		dt = datetime.fromisoformat("2021-12-31")
+		w = determine_consecutive_week_number(dt)
+		self.assertEqual(w, "52")