Specific return types for values and values list (#53)

* Instead of using Literal types, overload QuerySet.values_list in the plugin. Fixes #43.

- Add a couple of extra type checks that Django makes:
  1) 'flat' and 'named' can't be used together.
  2) 'flat' is not valid when values_list is called with more than one field.

* Determine better row types for values_list/values based on fields specified.

- In the case of values_list, we use a Row type with either a single primitive, Tuple, or NamedTuple.
- In the case of values, we use a TypedDict.
- In both cases, Any is used as a fallback for individual fields if those fields cannot be resolved.

A couple other fixes I made along the way:
- Don't create reverse relation for ForeignKeys with related_name='+'
- Don't skip creating other related managers in AddRelatedManagers if a dynamic value is encountered
  for related_name parameter, or if the type cannot be determined.

* Fix for TypedDict so that they are considered anonymous.

* Clean up some comments.

* Implement making TypedDict anonymous in a way that doesn't crash sometimes.

* Fix flake8 errors.

* Remove even uglier hack about making TypedDict anonymous.

* Address review comments. Write a few better comments inside tests.

* Fix crash when running with mypyc ("interpreted classes cannot inherit from compiled") due to the way I extended TypedDictType.

- Implemented the hack in another way that works on mypyc.
- Added a couple extra tests of accessing 'id' / 'pk' via values_list.

* Fix flake8 errors.

* Support annotation expressions (use type Any) for TypedDicts row types returned by values_list.

- Bonus points: handle values_list gracefully (use type Any) where Tuples are returned
  where some of the fields arguments are not string literals.

mypy_django_plugin/transformers/init_create.py

@@ -6,7 +6,6 @@ from mypy.plugin import FunctionContext, MethodContext
 from mypy.types import AnyType, Instance, Type, TypeOfAny
 
 from mypy_django_plugin import helpers
-from mypy_django_plugin.transformers.fields import get_private_descriptor_type
 
 
 def extract_base_pointer_args(model: TypeInfo) -> Set[str]:
@@ -162,8 +161,8 @@ def extract_expected_types(ctx: FunctionContext, model: TypeInfo,
                             if not pk_type:
                                 # extract set type of AutoField
                                 autofield_info = api.lookup_typeinfo('django.db.models.fields.AutoField')
-                                pk_type = get_private_descriptor_type(autofield_info, '_pyi_private_set_type',
-                                                                      is_nullable=is_nullable)
+                                pk_type = helpers.get_private_descriptor_type(autofield_info, '_pyi_private_set_type',
+                                                                              is_nullable=is_nullable)
                             related_primary_key_type = pk_type
 
                         if is_init:
@@ -185,8 +184,8 @@ def extract_expected_types(ctx: FunctionContext, model: TypeInfo,
 
                         # if CharField(blank=True,...) and not nullable, then field can be None in __init__
                         elif (
-                            helpers.has_any_of_bases(typ.type, (helpers.CHAR_FIELD_FULLNAME,)) and is_init and
-                            field_metadata.get('blank', False) and not field_metadata.get('null', False)
+                                helpers.has_any_of_bases(typ.type, (helpers.CHAR_FIELD_FULLNAME,)) and is_init and
+                                field_metadata.get('blank', False) and not field_metadata.get('null', False)
                         ):
                             field_type = helpers.make_optional(field_type)