Add missing admin filter and fix model indexes (typeddjango#149)

Hello, 

this PR actually makes two changes:

- add the missing `EmptyFieldListFilter`.
- fix the model `Index` class which also accepts positional parameters.

I am not sure if this is the right way to contribute to this repository.

- Is it ok to submit both changes in a single PR?
- How can I be sure everything is working fine? (a.k.a. tests)

django-stubs/contrib/admin/filters.pyi

@@ -121,3 +121,8 @@ class RelatedOnlyFieldListFilter(RelatedFieldListFilter):
     lookup_val_isnull: None
     title: str
     used_parameters: Dict[Any, Any]
+
+class EmptyFieldListFilter(FieldListFilter):
+    lookup_kwarg: str
+    lookup_val: Any
+    def choices(self, changelist: Any) -> Iterator[dict[str, Any]]: ...

django-stubs/db/models/indexes.pyi

@@ -3,6 +3,7 @@ from typing import Any, List, Optional, Sequence, Tuple, Type
 from django.db.backends.base.schema import BaseDatabaseSchemaEditor
 from django.db.backends.ddl_references import Statement
 from django.db.models.base import Model
+from django.db.models.expressions import BaseExpression, Combinable
 from django.db.models.query_utils import Q
 
 class Index:
@@ -15,15 +16,19 @@ class Index:
     db_tablespace: Optional[str] = ...
     opclasses: Sequence[str] = ...
     condition: Optional[Q] = ...
+    expressions: Sequence[BaseExpression | Combinable] = ...
+
     def __init__(
         self,
-        *,
+        *expressions: BaseExpression | Combinable | str,
         fields: Sequence[str] = ...,
         name: Optional[str] = ...,
         db_tablespace: Optional[str] = ...,
         opclasses: Sequence[str] = ...,
         condition: Optional[Q] = ...
     ) -> None: ...
+    @property
+    def contains_expressions(self) -> bool: ...
     def check_name(self) -> List[str]: ...
     def create_sql(
         self,

django-stubs/urls/conf.pyi

@@ -14,7 +14,9 @@ from ..conf.urls import IncludedURLConf
 from ..http.response import HttpResponseBase
 from .resolvers import URLPattern, URLResolver
 
-_ResponseType = Union[HttpResponseBase, Coroutine[Any, Any, HttpResponseBase], Coroutine[Any, Any, None]]
+_ResponseType = Union[
+    HttpResponseBase, Coroutine[Any, Any, HttpResponseBase], Coroutine[Any, Any, None]
+]
 
 def include(
     arg: Any, namespace: Optional[str] = ...

django-stubs/utils/html.pyi

@@ -17,7 +17,9 @@ def json_script(value: Any, element_id: str) -> SafeText: ...
 def conditional_escape(text: Any) -> str: ...
 def format_html(format_string: str, *args: Any, **kwargs: Any) -> SafeText: ...
 def format_html_join(
-    sep: str, format_string: str, args_generator: Union[Iterable[Any], Iterable[Tuple[str]]]
+    sep: str,
+    format_string: str,
+    args_generator: Union[Iterable[Any], Iterable[Tuple[str]]],
 ) -> SafeText: ...
 def linebreaks(value: Any, autoescape: bool = ...) -> str: ...
 

tests/trout/admin.py

@@ -0,0 +1,16 @@
+from django.contrib import admin
+
+from .models import IndexModel
+
+
+@admin.register(IndexModel)
+class IndexModelAdmin(admin.ModelAdmin[IndexModel]):
+    list_display = [
+        "pub_date", "title", "author", "height", "weight",
+    ]
+    list_filter = [
+        ("author", admin.filters.EmptyFieldListFilter),
+        "pub_date",
+    ]
+
+

tests/trout/models.py

@@ -1,3 +1,6 @@
+# Disable because pyright is not able to understand the Meta nested class override in models.
+# pyright: reportIncompatibleVariableOverride=false
+
 import sys
 from collections import namedtuple
 from datetime import time, timedelta
@@ -21,6 +24,7 @@
 from django.core.cache import cache
 from django.db import connection, connections, models
 from django.db.backends.utils import CursorWrapper
+from django.db.models.functions import Lower, Round
 from django.db.models.manager import ManyToManyRelatedManager
 from django.http.request import HttpRequest
 from django.http.response import HttpResponse
@@ -1030,3 +1034,24 @@ def __init__(self, *args: Any, **kwargs: Any) -> None:
 
 
 AuthUser.objects.create_superuser(username="foo", email=None, password=None)
+
+
+class IndexModel(models.Model):
+    title = models.TextField()
+    author = models.ForeignKey[Optional[User]](User, on_delete=models.CASCADE, null=True)
+    pub_date = models.DateTimeField()
+    height = models.IntegerField()
+    weight = models.IntegerField()
+
+    class Meta:
+        # from: https://docs.djangoproject.com/en/3.2/ref/models/indexes/#expressions
+        indexes = [
+            models.Index(
+                Lower("title").desc(), "pub_date", name="lower_title_date_idx"
+            ),
+            models.Index(
+                models.F("height") * models.F("weight"),
+                Round("weight"),
+                name="calc_idx",
+            ),
+        ]