self reference support for foreignkeys

mypy_django_plugin/helpers.py

@@ -50,9 +50,15 @@ class InvalidModelString(ValueError):
         self.model_string = model_string
 
 
-def get_model_fullname_from_string(expr: StrExpr,
+class SelfReference(ValueError):
+    pass
+
+
+def get_model_fullname_from_string(model_string: str,
                                    all_modules: Dict[str, MypyFile]) -> Optional[str]:
-    model_string = expr.value
+    if model_string == 'self':
+        raise SelfReference()
+
     if '.' not in model_string:
         raise InvalidModelString(model_string)
 

mypy_django_plugin/plugins/models.py

@@ -132,6 +132,8 @@ class AddRelatedManagers(ModelClassInitializer):
                             ref_to_fullname = extract_ref_to_fullname(rvalue,
                                                                       module_file=module_file,
                                                                       all_modules=self.api.modules)
+                        except helpers.SelfReference:
+                            ref_to_fullname = defn.fullname
                         except helpers.InvalidModelString as exc:
                             self.api.fail(f'Invalid value for a to= parameter: {exc.model_string!r}',
                                           Context(line=rvalue.line))
@@ -183,7 +185,7 @@ def extract_ref_to_fullname(rvalue_expr: CallExpr,
     if isinstance(to_expr, NameExpr):
         return module_file.names[to_expr.name].fullname
     elif isinstance(to_expr, StrExpr):
-        typ_fullname = helpers.get_model_fullname_from_string(to_expr, all_modules)
+        typ_fullname = helpers.get_model_fullname_from_string(to_expr.value, all_modules)
         if typ_fullname is None:
             return None
         return typ_fullname

mypy_django_plugin/plugins/related_fields.py

@@ -2,7 +2,7 @@ import typing
 from typing import Optional, cast
 
 from mypy.checker import TypeChecker
-from mypy.nodes import StrExpr, TypeInfo, Context
+from mypy.nodes import StrExpr, TypeInfo
 from mypy.plugin import FunctionContext
 from mypy.types import Type, CallableType, Instance, AnyType, TypeOfAny
 
@@ -31,8 +31,12 @@ def get_valid_to_value_or_none(ctx: FunctionContext) -> Optional[Instance]:
         if not isinstance(to_arg_expr, StrExpr):
             # not string, not supported
             return None
-        model_fullname = helpers.get_model_fullname_from_string(to_arg_expr,
+        try:
+            model_fullname = helpers.get_model_fullname_from_string(to_arg_expr.value,
                                                                     all_modules=api.modules)
+        except helpers.SelfReference:
+            model_fullname = api.tscope.classes[-1].fullname()
+
         if model_fullname is None:
             return None
         model_info = helpers.lookup_fully_qualified_generic(model_fullname,

test-data/typecheck/related_fields.test

@@ -214,3 +214,17 @@ from django.db import models
 class App(models.Model):
     pass
 [out]
+
+[CASE foreign_key_with_self]
+from django.db import models
+class User(models.Model):
+    parent = models.ForeignKey('self', on_delete=models.CASCADE)
+reveal_type(User().parent)  # E: Revealed type is 'main.User*'
+[out]
+
+[CASE many_to_many_with_self]
+from django.db import models
+class User(models.Model):
+    friends = models.ManyToManyField('self', on_delete=models.CASCADE)
+reveal_type(User().friends)  # E: Revealed type is 'django.db.models.manager.RelatedManager[main.User*]'
+[out]