refactor!: better API contracts for virtual doctype

Current APIs implement class methods as instance method, which is
problamamtic while implementing methods. E.g. If load_from_db doesn't
like empty docname then all class method will stop working.

This change while breaking is essential for usability of virtual
doctype.

frappe/core/doctype/test/test.py

@@ -8,7 +8,7 @@ from frappe.model.document import Document
 
 
 class test(Document):
-	def db_insert(self):
+	def db_insert(self, *args, **kwargs):
 		d = self.get_valid_dict(convert_dates_to_str=True)
 		with open("data_file.json", "w+") as read_file:
 			json.dump(d, read_file)
@@ -18,26 +18,22 @@ class test(Document):
 			d = json.load(read_file)
 			super(Document, self).__init__(d)
 
-	def db_update(self):
+	def db_update(self, *args, **kwargs):
 		d = self.get_valid_dict(convert_dates_to_str=True)
 		with open("data_file.json", "w+") as read_file:
 			json.dump(d, read_file)
 
-	def get_list(self, args):
+	@staticmethod
+	def get_list(args):
 		with open("data_file.json") as read_file:
 			return [frappe._dict(json.load(read_file))]
 
-	def get_value(self, fields, filters, **kwargs):
-		# return []
-		with open("data_file.json") as read_file:
-			return [json.load(read_file)]
+	@staticmethod
+	def get_count(args):
+		return 5
 
-	def get_count(self, args):
-		# return []
-		with open("data_file.json") as read_file:
-			return [json.load(read_file)]
-
-	def get_stats(self, args):
+	@staticmethod
+	def get_stats(args):
 		# return []
 		with open("data_file.json") as read_file:
 			return [json.load(read_file)]

frappe/desk/reportview.py

@@ -24,7 +24,7 @@ def get():
 	# If virtual doctype get data from controller het_list method
 	if is_virtual_doctype(args.doctype):
 		controller = get_controller(args.doctype)
-		data = compress(controller(args.doctype).get_list(args))
+		data = compress(controller.get_list(args))
 	else:
 		data = compress(execute(**args), args=args)
 	return data
@@ -37,7 +37,7 @@ def get_list():
 
 	if is_virtual_doctype(args.doctype):
 		controller = get_controller(args.doctype)
-		data = controller(args.doctype).get_list(args)
+		data = controller.get_list(args)
 	else:
 		# uncompressed (refactored from frappe.model.db_query.get_list)
 		data = execute(**args)
@@ -52,7 +52,7 @@ def get_count():
 
 	if is_virtual_doctype(args.doctype):
 		controller = get_controller(args.doctype)
-		data = controller(args.doctype).get_count(args)
+		data = controller.get_count(args)
 	else:
 		distinct = "distinct " if args.distinct == "true" else ""
 		args.fields = [f"count({distinct}`tab{args.doctype}`.name) as total_count"]
@@ -528,7 +528,7 @@ def get_sidebar_stats(stats, doctype, filters=None):
 	if is_virtual_doctype(doctype):
 		controller = get_controller(doctype)
 		args = {"stats": stats, "filters": filters}
-		data = controller(doctype).get_stats(args)
+		data = controller.get_stats(args)
 	else:
 		data = get_stats(stats, doctype, filters)
 

frappe/model/virtual_doctype.py

@@ -0,0 +1,46 @@
+from typing import Protocol
+
+
+class VirtualDoctype(Protocol):
+	"""This class documents requirements that must be met by a doctype controller to function as virtual doctype
+
+
+	Additional requirements:
+	- DocType controller has to inherit from `frappe.model.document.Document` class
+
+	Note:
+	- "Backend" here means any storage service, it can be a database, flat file or network call to API.
+	"""
+
+	# ============ class/static methods ============
+
+	@staticmethod
+	def get_list(args):
+		"""Similar to reportview.get_list"""
+		...
+
+	@staticmethod
+	def get_count(args) -> int:
+		"""Similar to reportview.get_count, return total count of documents on listview."""
+		...
+
+	@staticmethod
+	def get_stats(args):
+		"""Similar to reportview.get_stats, return sidebar stats."""
+		...
+
+	# ============ instance methods ============
+
+	def db_insert(self, *args, **kwargs) -> None:
+		"""Serialize the `Document` object and insert it in backend."""
+		...
+
+	def load_from_db(self) -> None:
+		"""Using self.name initialize current document from backend data.
+
+		This is responsible for updatinng __dict__ of class with all the fields on doctype."""
+		...
+
+	def db_update(self, *args, **kwargs):
+		"""Serialize the `Document` object and update existing document in backend."""
+		...

frappe/modules/utils.py

@@ -296,22 +296,25 @@ def make_boilerplate(template, doc, opts=None):
 		custom_controller = "pass"
 		if doc.get("is_virtual"):
 			custom_controller = """
-	def db_insert(self):
+	def db_insert(self, *args, **kwargs):
 		pass
 
 	def load_from_db(self):
 		pass
 
-	def db_update(self):
+	def db_update(self, *args, **kwargs):
 		pass
 
-	def get_list(self, args):
+	@staticmethod
+	def get_list(args):
 		pass
 
-	def get_count(self, args):
+	@staticmethod
+	def get_count(args):
 		pass
 
-	def get_stats(self, args):
+	@staticmethod
+	def get_stats(args):
 		pass"""
 
 		with open(target_file_path, "w") as target: