Support returning the correct values for the different QuerySet metho…

…ds when using .values() and .values_list(). (#33)

* Support returning the correct values for the different QuerySet methods when using .values() and .values_list().

* Fix slicing on QuerySet. Fix django queries test, and remove some ignored errors that are no longer needed.

* Remove accidental change in RawQuerySet.

* Readded some still-necessary ignores to aggregation django test.

* Add more tests of first/last/earliest/last/__getitem__, per mkurnikov's comments.

- Fix .iterator()

* Re-add Iterator as base-class of QuerySet.

* Make QuerySet a Collection.

* - Fix return type for QuerySet.select_for_update().
- Use correct return type for QuerySet.dates() / QuerySet.datetimes().
- Use correct type params in return type for QuerySet.__and__ / QuerySet.__or__
- Re-add Sized as base class for QuerySet.
- Add test of .all() for all _Row types.
- Add test of .get() for all _Row types.
- Remove some redundant QuerySet method tests.

* Automatically fill in second type parameter for QuerySet.

... if second parameter is omitted.

django-stubs/db/models/manager.pyi

@@ -5,7 +5,7 @@ from django.db.models.query import QuerySet
 
 _T = TypeVar("_T", bound=Model, covariant=True)
 
-class BaseManager(QuerySet[_T]):
+class BaseManager(QuerySet[_T, _T]):
     creation_counter: int = ...
     auto_created: bool = ...
     use_in_migrations: bool = ...
@@ -21,7 +21,7 @@ class BaseManager(QuerySet[_T]):
     def _get_queryset_methods(cls, queryset_class: type) -> Dict[str, Any]: ...
     def contribute_to_class(self, model: Type[Model], name: str) -> None: ...
     def db_manager(self, using: Optional[str] = ..., hints: Optional[Dict[str, Model]] = ...) -> Manager: ...
-    def get_queryset(self) -> QuerySet[_T]: ...
+    def get_queryset(self) -> QuerySet[_T, _T]: ...
 
 class Manager(BaseManager[_T]): ...
 

django-stubs/db/models/query.pyi

@@ -1,3 +1,4 @@
+import datetime
 from typing import (
     Any,
     Dict,
@@ -13,6 +14,9 @@ from typing import (
     TypeVar,
     Union,
     overload,
+    Generic,
+    NamedTuple,
+    Collection,
 )
 
 from django.db.models.base import Model
@@ -46,7 +50,7 @@ class FlatValuesListIterable(BaseIterable):
 
 _T = TypeVar("_T", bound=models.Model, covariant=True)
 
-class QuerySet(Iterable[_T], Sized):
+class QuerySet(Generic[_T, _Row], Collection[_Row], Sized):
     query: Query
     def __init__(
         self,
@@ -58,32 +62,33 @@ class QuerySet(Iterable[_T], Sized):
     @classmethod
     def as_manager(cls) -> Manager[Any]: ...
     def __len__(self) -> int: ...
-    def __iter__(self) -> Iterator[_T]: ...
+    def __iter__(self) -> Iterator[_Row]: ...
+    def __contains__(self, x: object) -> bool: ...
+    @overload
+    def __getitem__(self, i: int) -> _Row: ...
+    @overload
+    def __getitem__(self, s: slice) -> QuerySet[_T, _Row]: ...
     def __bool__(self) -> bool: ...
     def __class_getitem__(cls, item: Type[_T]):
         pass
     def __getstate__(self) -> Dict[str, Any]: ...
-    @overload
-    def __getitem__(self, k: int) -> _T: ...
-    @overload
-    def __getitem__(self, k: str) -> Any: ...
-    @overload
-    def __getitem__(self, k: slice) -> QuerySet[_T]: ...
-    def __and__(self, other: QuerySet) -> QuerySet: ...
-    def __or__(self, other: QuerySet) -> QuerySet: ...
-    def iterator(self, chunk_size: int = ...) -> Iterator[_T]: ...
+    # __and__ and __or__ ignore the other QuerySet's _Row type parameter because they use the same row type as the self QuerySet.
+    # Technically, the other QuerySet must be of the same type _T, but _T is covariant
+    def __and__(self, other: QuerySet[_T, Any]) -> QuerySet[_T, _Row]: ...
+    def __or__(self, other: QuerySet[_T, Any]) -> QuerySet[_T, _Row]: ...
+    def iterator(self, chunk_size: int = ...) -> Iterator[_Row]: ...
     def aggregate(self, *args: Any, **kwargs: Any) -> Dict[str, Any]: ...
-    def get(self, *args: Any, **kwargs: Any) -> _T: ...
+    def get(self, *args: Any, **kwargs: Any) -> _Row: ...
     def create(self, **kwargs: Any) -> _T: ...
     def bulk_create(self, objs: Iterable[Model], batch_size: Optional[int] = ...) -> List[_T]: ...
     def get_or_create(self, defaults: Optional[MutableMapping[str, Any]] = ..., **kwargs: Any) -> Tuple[_T, bool]: ...
     def update_or_create(
         self, defaults: Optional[MutableMapping[str, Any]] = ..., **kwargs: Any
     ) -> Tuple[_T, bool]: ...
-    def earliest(self, *fields: Any, field_name: Optional[Any] = ...) -> _T: ...
-    def latest(self, *fields: Any, field_name: Optional[Any] = ...) -> _T: ...
-    def first(self) -> Optional[_T]: ...
-    def last(self) -> Optional[_T]: ...
+    def earliest(self, *fields: Any, field_name: Optional[Any] = ...) -> _Row: ...
+    def latest(self, *fields: Any, field_name: Optional[Any] = ...) -> _Row: ...
+    def first(self) -> Optional[_Row]: ...
+    def last(self) -> Optional[_Row]: ...
     def in_bulk(self, id_list: Iterable[Any] = ..., *, field_name: str = ...) -> Dict[Any, _T]: ...
     def delete(self) -> Tuple[int, Dict[str, int]]: ...
     def update(self, **kwargs: Any) -> int: ...
@@ -93,31 +98,38 @@ class QuerySet(Iterable[_T], Sized):
     def raw(
         self, raw_query: str, params: Any = ..., translations: Optional[Dict[str, str]] = ..., using: None = ...
     ) -> RawQuerySet: ...
-    def values(self, *fields: Union[str, Combinable], **expressions: Any) -> QuerySet: ...
-    def values_list(self, *fields: Union[str, Combinable], flat: bool = ..., named: bool = ...) -> QuerySet: ...
-    # @overload
-    # def values_list(self, *fields: Union[str, Combinable], named: Literal[True]) -> NamedValuesListIterable: ...
-    # @overload
-    # def values_list(self, *fields: Union[str, Combinable], flat: Literal[True]) -> FlatValuesListIterable: ...
-    # @overload
-    # def values_list(self, *fields: Union[str, Combinable]) -> ValuesListIterable: ...
-    def dates(self, field_name: str, kind: str, order: str = ...) -> QuerySet: ...
-    def datetimes(self, field_name: str, kind: str, order: str = ..., tzinfo: None = ...) -> QuerySet: ...
-    def none(self) -> QuerySet[_T]: ...
-    def all(self) -> QuerySet[_T]: ...
-    def filter(self, *args: Any, **kwargs: Any) -> QuerySet[_T]: ...
-    def exclude(self, *args: Any, **kwargs: Any) -> QuerySet[_T]: ...
-    def complex_filter(self, filter_obj: Any) -> QuerySet[_T]: ...
+    def values(self, *fields: Union[str, Combinable], **expressions: Any) -> QuerySet[_T, Dict[str, Any]]: ...
+    @overload
+    def values_list(
+        self, *fields: Union[str, Combinable], flat: Literal[False] = ..., named: Literal[True]
+    ) -> QuerySet[_T, NamedTuple]: ...
+    @overload
+    def values_list(
+        self, *fields: Union[str, Combinable], flat: Literal[True], named: Literal[False] = ...
+    ) -> QuerySet[_T, Any]: ...
+    @overload
+    def values_list(
+        self, *fields: Union[str, Combinable], flat: Literal[False] = ..., named: Literal[False] = ...
+    ) -> QuerySet[_T, Tuple]: ...
+    def dates(self, field_name: str, kind: str, order: str = ...) -> QuerySet[_T, datetime.date]: ...
+    def datetimes(
+        self, field_name: str, kind: str, order: str = ..., tzinfo: None = ...
+    ) -> QuerySet[_T, datetime.datetime]: ...
+    def none(self) -> QuerySet[_T, _Row]: ...
+    def all(self) -> QuerySet[_T, _Row]: ...
+    def filter(self, *args: Any, **kwargs: Any) -> QuerySet[_T, _Row]: ...
+    def exclude(self, *args: Any, **kwargs: Any) -> QuerySet[_T, _Row]: ...
+    def complex_filter(self, filter_obj: Any) -> QuerySet[_T, _Row]: ...
     def count(self) -> int: ...
-    def union(self, *other_qs: Any, all: bool = ...) -> QuerySet[_T]: ...
-    def intersection(self, *other_qs: Any) -> QuerySet[_T]: ...
-    def difference(self, *other_qs: Any) -> QuerySet[_T]: ...
-    def select_for_update(self, nowait: bool = ..., skip_locked: bool = ..., of: Tuple = ...) -> QuerySet: ...
-    def select_related(self, *fields: Any) -> QuerySet[_T]: ...
-    def prefetch_related(self, *lookups: Any) -> QuerySet[_T]: ...
-    def annotate(self, *args: Any, **kwargs: Any) -> QuerySet[_T]: ...
-    def order_by(self, *field_names: Any) -> QuerySet[_T]: ...
-    def distinct(self, *field_names: Any) -> QuerySet[_T]: ...
+    def union(self, *other_qs: Any, all: bool = ...) -> QuerySet[_T, _Row]: ...
+    def intersection(self, *other_qs: Any) -> QuerySet[_T, _Row]: ...
+    def difference(self, *other_qs: Any) -> QuerySet[_T, _Row]: ...
+    def select_for_update(self, nowait: bool = ..., skip_locked: bool = ..., of: Tuple = ...) -> QuerySet[_T, _Row]: ...
+    def select_related(self, *fields: Any) -> QuerySet[_T, _Row]: ...
+    def prefetch_related(self, *lookups: Any) -> QuerySet[_T, _Row]: ...
+    def annotate(self, *args: Any, **kwargs: Any) -> QuerySet[_T, _Row]: ...
+    def order_by(self, *field_names: Any) -> QuerySet[_T, _Row]: ...
+    def distinct(self, *field_names: Any) -> QuerySet[_T, _Row]: ...
     def extra(
         self,
         select: Optional[Dict[str, Any]] = ...,
@@ -126,11 +138,11 @@ class QuerySet(Iterable[_T], Sized):
         tables: Optional[List[str]] = ...,
         order_by: Optional[Sequence[str]] = ...,
         select_params: Optional[Sequence[Any]] = ...,
-    ) -> QuerySet[_T]: ...
-    def reverse(self) -> QuerySet[_T]: ...
-    def defer(self, *fields: Any) -> QuerySet[_T]: ...
-    def only(self, *fields: Any) -> QuerySet[_T]: ...
-    def using(self, alias: Optional[str]) -> QuerySet[_T]: ...
+    ) -> QuerySet[_T, _Row]: ...
+    def reverse(self) -> QuerySet[_T, _Row]: ...
+    def defer(self, *fields: Any) -> QuerySet[_T, _Row]: ...
+    def only(self, *fields: Any) -> QuerySet[_T, _Row]: ...
+    def using(self, alias: Optional[str]) -> QuerySet[_T, _Row]: ...
     @property
     def ordered(self) -> bool: ...
     @property
@@ -159,7 +171,7 @@ class RawQuerySet(Iterable[_T], Sized):
     @overload
     def __getitem__(self, k: str) -> Any: ...
     @overload
-    def __getitem__(self, k: slice) -> QuerySet[_T]: ...
+    def __getitem__(self, k: slice) -> RawQuerySet[_T]: ...
     @property
     def columns(self) -> List[str]: ...
     @property

django-stubs/shortcuts.pyi

@@ -31,6 +31,6 @@ def redirect(
 
 _T = TypeVar("_T", bound=Model)
 
-def get_object_or_404(klass: Union[Type[_T], Manager[_T], QuerySet[_T]], *args: Any, **kwargs: Any) -> _T: ...
-def get_list_or_404(klass: Union[Type[_T], Manager[_T], QuerySet[_T]], *args: Any, **kwargs: Any) -> List[_T]: ...
+def get_object_or_404(klass: Union[Type[_T], Manager[_T], QuerySet[_T, _T]], *args: Any, **kwargs: Any) -> _T: ...
+def get_list_or_404(klass: Union[Type[_T], Manager[_T], QuerySet[_T, _T]], *args: Any, **kwargs: Any) -> List[_T]: ...
 def resolve_url(to: Union[Callable, Model, str], *args: Any, **kwargs: Any) -> str: ...

mypy_django_plugin/main.py

@@ -1,3 +1,5 @@
+from functools import partial
+
 import os
 from typing import Callable, Dict, Optional, Union, cast
 
@@ -6,7 +8,7 @@
 from mypy.options import Options
 from mypy.plugin import (
     AttributeContext, ClassDefContext, FunctionContext, MethodContext, Plugin,
-)
+    AnalyzeTypeContext)
 from mypy.types import (
     AnyType, CallableType, Instance, NoneTyp, Type, TypeOfAny, TypeType, UnionType,
 )
@@ -80,6 +82,18 @@ def determine_proper_manager_type(ctx: FunctionContext) -> Type:
         return ret
 
 
+def set_first_generic_param_as_default_for_second(fullname: str, ctx: AnalyzeTypeContext) -> Type:
+    if not ctx.type.args:
+        return ctx.api.named_type(fullname, [AnyType(TypeOfAny.explicit),
+                                             AnyType(TypeOfAny.explicit)])
+    args = ctx.type.args
+    if len(args) == 1:
+        args = [args[0], args[0]]
+
+    analyzed_args = [ctx.api.analyze_type(arg) for arg in args]
+    return ctx.api.named_type(fullname, analyzed_args)
+
+
 def return_user_model_hook(ctx: FunctionContext) -> Type:
     api = cast(TypeChecker, ctx.api)
     setting_expr = helpers.get_setting_expr(api, 'AUTH_USER_MODEL')
@@ -266,6 +280,14 @@ def _get_current_form_bases(self) -> Dict[str, int]:
         else:
             return {}
 
+    def _get_current_queryset_bases(self) -> Dict[str, int]:
+        model_sym = self.lookup_fully_qualified(helpers.QUERYSET_CLASS_FULLNAME)
+        if model_sym is not None and isinstance(model_sym.node, TypeInfo):
+            return (helpers.get_django_metadata(model_sym.node)
+                    .setdefault('queryset_bases', {helpers.QUERYSET_CLASS_FULLNAME: 1}))
+        else:
+            return {}
+
     def get_function_hook(self, fullname: str
                           ) -> Optional[Callable[[FunctionContext], Type]]:
         if fullname == 'django.contrib.auth.get_user_model':
@@ -344,6 +366,14 @@ def get_attribute_hook(self, fullname: str
 
         return extract_and_return_primary_key_of_bound_related_field_parameter
 
+    def get_type_analyze_hook(self, fullname: str
+                              ) -> Optional[Callable[[AnalyzeTypeContext], Type]]:
+        queryset_bases = self._get_current_queryset_bases()
+        if fullname in queryset_bases:
+            return partial(set_first_generic_param_as_default_for_second, fullname)
+
+        return None
+
 
 def plugin(version):
     return DjangoPlugin

scripts/typecheck_tests.py

@@ -91,20 +91,11 @@
         'Argument "is_dst" to "localize" of "BaseTzInfo" has incompatible type "None"; expected "bool"'
     ],
     'aggregation': [
-        'Incompatible types in assignment (expression has type "QuerySet[Any]", variable has type "List[Any]")',
         '"as_sql" undefined in superclass',
-        'Incompatible types in assignment (expression has type "FlatValuesListIterable", '
-        + 'variable has type "ValuesListIterable")',
         'Incompatible type for "contact" of "Book" (got "Optional[Author]", expected "Union[Author, Combinable]")',
         'Incompatible type for "publisher" of "Book" (got "Optional[Publisher]", '
         + 'expected "Union[Publisher, Combinable]")'
     ],
-    'aggregation_regress': [
-        'Incompatible types in assignment (expression has type "List[str]", variable has type "QuerySet[Author]")',
-        'Incompatible types in assignment (expression has type "FlatValuesListIterable", '
-        + 'variable has type "QuerySet[Any]")',
-        'Too few arguments for "count" of "Sequence"'
-    ],
     'apps': [
         'Incompatible types in assignment (expression has type "str", target has type "type")',
         '"Callable[[bool, bool], List[Type[Model]]]" has no attribute "cache_clear"'
@@ -159,9 +150,6 @@
     'db_typecasts': [
         '"object" has no attribute "__iter__"; maybe "__str__" or "__dir__"? (not iterable)'
     ],
-    'expressions': [
-        'Argument 1 to "Subquery" has incompatible type "Sequence[Dict[str, Any]]"; expected "QuerySet[Any]"'
-    ],
     'from_db_value': [
         'has no attribute "vendor"'
     ],
@@ -199,9 +187,9 @@
     ],
     'get_object_or_404': [
         'Argument 1 to "get_object_or_404" has incompatible type "str"; '
-        + 'expected "Union[Type[<nothing>], QuerySet[<nothing>]]"',
+        + 'expected "Union[Type[<nothing>], QuerySet[<nothing>, <nothing>]]"',
         'Argument 1 to "get_list_or_404" has incompatible type "List[Type[Article]]"; '
-        + 'expected "Union[Type[<nothing>], QuerySet[<nothing>]]"',
+        + 'expected "Union[Type[<nothing>], QuerySet[<nothing>, <nothing>]]"',
         'CustomClass'
     ],
     'get_or_create': [
@@ -227,10 +215,6 @@
     'many_to_one': [
         'Incompatible type for "parent" of "Child" (got "None", expected "Union[Parent, Combinable]")'
     ],
-    'model_inheritance_regress': [
-        'Incompatible types in assignment (expression has type "List[Supplier]", '
-        + 'variable has type "QuerySet[Supplier]")'
-    ],
     'model_meta': [
         '"object" has no attribute "items"',
         '"Field" has no attribute "many_to_many"'
@@ -305,7 +289,8 @@
     ],
     'queries': [
         'Incompatible types in assignment (expression has type "None", variable has type "str")',
-        'Invalid index type "Optional[str]" for "Dict[str, int]"; expected type "str"'
+        'Invalid index type "Optional[str]" for "Dict[str, int]"; expected type "str"',
+        'No overload variant of "values_list" of "QuerySet" matches argument types "str", "bool", "bool"',
     ],
     'requests': [
         'Incompatible types in assignment (expression has type "Dict[str, str]", variable has type "QueryDict")'
@@ -314,7 +299,7 @@
         'Argument 1 to "TextIOWrapper" has incompatible type "HttpResponse"; expected "IO[bytes]"'
     ],
     'prefetch_related': [
-        'Incompatible types in assignment (expression has type "List[Room]", variable has type "QuerySet[Room]")',
+        'Incompatible types in assignment (expression has type "List[Room]", variable has type "QuerySet[Room, Room]")',
         '"None" has no attribute "__iter__"',
         'has no attribute "read_by"'
     ],