Fix types for class Meta options (#2806)

Author: sloria

CHANGELOG.rst

@@ -4,6 +4,11 @@ Changelog
 (unreleased)
 ************
 
+Bug fixes:
+
+- Typing: Fix type annotations for `class Meta <marshmallow.Schema.Meta>` options (:issue:`2804`).
+  Thanks :user:`lawrence-law` for reporting.
+
 Other changes:
 
 - Remove default value for the ``data`` param of `Nested._deserialize <marshmallow.fields.Nested._deserialize>` (:issue:`2802`).

src/marshmallow/schema.py

@@ -384,9 +384,9 @@ class Meta(Schema.Opts):
         .. versionchanged:: 3.26.0 Deprecate `ordered`. Field order is preserved by default.
         """
 
-        fields: typing.ClassVar[tuple[Field] | list[Field]]
+        fields: typing.ClassVar[tuple[str, ...] | list[str]]
         """Fields to include in the (de)serialized result"""
-        additional: typing.ClassVar[tuple[Field] | list[Field]]
+        additional: typing.ClassVar[tuple[str, ...] | list[str]]
         """Fields to include in addition to the explicitly declared fields.
         `additional <marshmallow.Schema.Meta.additional>` and `fields <marshmallow.Schema.Meta.fields>`
         are mutually-exclusive options.
@@ -396,7 +396,7 @@ class Meta(Schema.Opts):
         usually better to define fields as class variables, but you may need to
         use this option, e.g., if your fields are Python keywords.
         """
-        exclude: typing.ClassVar[tuple[Field] | list[Field]]
+        exclude: typing.ClassVar[tuple[str, ...] | list[str]]
         """Fields to exclude in the serialized result.
         Nested fields can be represented with dot delimiters.
         """
@@ -408,17 +408,20 @@ class Meta(Schema.Opts):
         """Default format for `DateTime <marshmallow.fields.DateTime>` fields."""
         timeformat: typing.ClassVar[str]
         """Default format for `Time <marshmallow.fields.Time>` fields."""
-        render_module: typing.ClassVar[types.RenderModule]
+
+        # FIXME: Use a more constrained type here.
+        # ClassVar[RenderModule] doesn't work.
+        render_module: typing.Any
         """ Module to use for `loads <marshmallow.Schema.loads>` and `dumps <marshmallow.Schema.dumps>`.
         Defaults to `json` from the standard library.
         """
         ordered: typing.ClassVar[bool]
         """If `True`, `Schema.dump <marshmallow.Schema.dump>` is a `collections.OrderedDict`."""
         index_errors: typing.ClassVar[bool]
         """If `True`, errors dictionaries will include the index of invalid items in a collection."""
-        load_only: typing.ClassVar[tuple[Field] | list[Field]]
+        load_only: typing.ClassVar[tuple[str, ...] | list[str]]
         """Fields to exclude from serialized results"""
-        dump_only: typing.ClassVar[tuple[Field] | list[Field]]
+        dump_only: typing.ClassVar[tuple[str, ...] | list[str]]
         """Fields to exclude from serialized results"""
         unknown: typing.ClassVar[str]
         """Whether to exclude, include, or raise an error for unknown fields in the data.

tests/mypy_test_cases/test_schema.py

@@ -0,0 +1,29 @@
+import json
+
+from marshmallow import EXCLUDE, Schema
+from marshmallow.fields import Integer, String
+
+
+# Test that valid `Meta` class attributes pass type checking
+class MySchema(Schema):
+    foo = String()
+    bar = Integer()
+
+    class Meta(Schema.Meta):
+        fields = ("foo", "bar")
+        additional = ("baz", "qux")
+        include = {
+            "foo2": String(),
+        }
+        exclude = ("bar", "baz")
+        many = True
+        dateformat = "%Y-%m-%d"
+        datetimeformat = "%Y-%m-%dT%H:%M:%S"
+        timeformat = "%H:%M:%S"
+        render_module = json
+        ordered = False
+        index_errors = True
+        load_only = ("foo", "bar")
+        dump_only = ("baz", "qux")
+        unknown = EXCLUDE
+        register = False