QuerySet.annotate improvements (#398)

* QuerySet.annotate returns self-type. Attribute access falls back to Any.

- QuerySets that have an annotated model do not report errors during .filter() when called with invalid fields.
- QuerySets that have an annotated model return ordinary dict rather than TypedDict for .values()
- QuerySets that have an annotated model return Any rather than typed Tuple for .values_list()

* Fix .annotate so it reuses existing annotated types. Fixes error in typechecking Django testsuite.

* Fix self-typecheck error

* Fix flake8

* Fix case of .values/.values_list before .annotate.

* Extra ignores for Django 2.2 tests (false positives due to tests assuming QuerySet.first() won't return None)

Fix mypy self-check.

* More tests + more precise typing in case annotate called before values_list.

Cleanup tests.

* Test and fix annotate in combination with values/values_list with no params.

* Remove line that does nothing :)

* Formatting fixes

* Address code review

* Fix quoting in tests after mypy changed things

* Use Final

* Use typing_extensions.Final

* Fixes after ValuesQuerySet -> _ValuesQuerySet refactor. Still not passing tests yet.

* Fix inheritance of _ValuesQuerySet and remove unneeded type ignores.

This allows the test
"annotate_values_or_values_list_before_or_after_annotate_broadens_type"
to pass.

* Make it possible to annotate user code with "annotated models", using PEP 583 Annotated type.

* Add docs

* Make QuerySet[_T] an external alias to _QuerySet[_T, _T].

This currently has the drawback that error messages display the internal type _QuerySet, with both type arguments.

See also discussion on #661 and #608.

Fixes #635: QuerySet methods on Managers (like .all()) now return QuerySets rather than Managers.

Address code review by @sobolevn.

* Support passing TypedDicts to WithAnnotations

* Add an example of an error to README regarding WithAnnotations + TypedDict.

* Fix runtime behavior of ValuesQuerySet alias (you can't extend Any, for example).

Fix some edge case with from_queryset after QuerySet changed to be an
alias to _QuerySet. Can't make a minimal test case as this only occurred
on a large internal codebase.

* Fix issue when using from_queryset in some cases when having an argument with a type annotation on the QuerySet.

The mypy docstring on anal_type says not to call defer() after it.

mypy_django_plugin/transformers/orm_lookups.py

@@ -5,6 +5,7 @@ from mypy.types import TypeOfAny
 
 from mypy_django_plugin.django.context import DjangoContext
 from mypy_django_plugin.lib import fullnames, helpers
+from mypy_django_plugin.lib.helpers import is_annotated_model_fullname
 
 
 def typecheck_queryset_filter(ctx: MethodContext, django_context: DjangoContext) -> MypyType:
@@ -29,7 +30,11 @@ def typecheck_queryset_filter(ctx: MethodContext, django_context: DjangoContext)
         ):
             provided_type = resolve_combinable_type(provided_type, django_context)
 
-        lookup_type = django_context.resolve_lookup_expected_type(ctx, model_cls, lookup_kwarg)
+        lookup_type: MypyType
+        if is_annotated_model_fullname(model_cls_fullname):
+            lookup_type = AnyType(TypeOfAny.implementation_artifact)
+        else:
+            lookup_type = django_context.resolve_lookup_expected_type(ctx, model_cls, lookup_kwarg)
         # Managers as provided_type is not supported yet
         if isinstance(provided_type, Instance) and helpers.has_any_of_bases(
             provided_type.type, (fullnames.MANAGER_CLASS_FULLNAME, fullnames.QUERYSET_CLASS_FULLNAME)