enable and pass mypy --strict

Author: altendky

mypy.ini

@@ -1,2 +1,3 @@
 [mypy]
 ignore_missing_imports = True
+strict = True

src/desert/__init__.py

@@ -12,8 +12,11 @@
     import attr._make
 
 
+T = t.TypeVar("T")
+
+
 def schema(
-    cls: t.Type, many: bool = False, meta: t.Dict[str, t.Any] = {}
+    cls: type, many: bool = False, meta: t.Dict[str, t.Any] = {}
 ) -> marshmallow.Schema:
     """Build a marshmallow schema *instance* for the class.
 
@@ -29,7 +32,7 @@ def schema(
 
 
 def schema_class(
-    cls: t.Type, meta: t.Dict[str, t.Any] = {}
+    cls: type, meta: t.Dict[str, t.Any] = {}
 ) -> t.Type[marshmallow.Schema]:
     """Build a marshmallow schema *class* for the class.
 
@@ -46,7 +49,7 @@ def schema_class(
 
 def metadata(
     field: marshmallow.fields.Field,
-) -> t.Dict["desert._make._DesertSentinel", t.Dict[t.Any, marshmallow.fields.Field]]:
+) -> t.Dict[object, object]:
     """Specify a marshmallow field in the field metadata.
 
     .. code-block:: python
@@ -56,7 +59,53 @@ def metadata(
     return {desert._make._DESERT_SENTINEL: {"marshmallow_field": field}}
 
 
-def field(marshmallow_field: marshmallow.fields.Field, **kw) -> dataclasses.Field:
+# TODO: maybe deprecate and rename metadata()
+create_metadata = metadata
+
+
+# These overloads lie about their return type just as both attrs and dataclasses
+# do so as to support the normal usage of `attribute: int = field()`
+@t.overload
+def field(
+    marshmallow_field: marshmallow.fields.Field,
+    *,
+    default: T,
+    metadata: t.Optional[t.Mapping[object, object]] = None,
+    **kw: object,
+) -> T:
+    ...
+
+
+@t.overload
+def field(
+    marshmallow_field: marshmallow.fields.Field,
+    *,
+    default_factory: t.Callable[[], T],
+    metadata: t.Optional[t.Mapping[object, object]] = None,
+    **kw: object,
+) -> T:
+    ...
+
+
+@t.overload
+def field(
+    marshmallow_field: marshmallow.fields.Field,
+    *,
+    metadata: t.Optional[t.Mapping[object, object]] = None,
+    **kw: object,
+) -> object:
+    ...
+
+
+# The return type hint of object is certainly a lie but fits a lot better with
+# the normal use of `x: int = desert.field()`.  Both dataclasses and attrs
+# prioritize hinting for this usage as well.  Perhaps someday we'll have a
+# plugin that indicates the actual type.
+def field(
+    marshmallow_field: marshmallow.fields.Field,
+    metadata: t.Optional[t.Mapping[object, object]] = None,
+    **kw: object,
+) -> object:
     """Specify a marshmallow field in the metadata for a ``dataclasses.dataclass``.
 
     .. code-block:: python
@@ -65,15 +114,61 @@ def field(marshmallow_field: marshmallow.fields.Field, **kw) -> dataclasses.Fiel
         class A:
             x: int = desert.field(marshmallow.fields.Int())
     """
-    meta = metadata(marshmallow_field)
-    meta.update(kw.pop("metadata", {}))
-    # typeshed hints it as Mapping[str, Any] without any obvious reason
-    # https://github.com/python/typeshed/blob/95a45eb4abd0c25849268983cb614e3bf6b9b264/stdlib/dataclasses.pyi#L81
-    # https://github.com/python/typeshed/pull/5823
-    return dataclasses.field(**kw, metadata=meta)  # type: ignore[arg-type]
-
-
-def ib(marshmallow_field: marshmallow.fields.Field, **kw) -> attr._make._CountingAttr:
+    if metadata is None:
+        metadata = {}
+
+    meta: t.Dict[object, object] = create_metadata(marshmallow_field)
+    meta.update(metadata)
+
+    # call-overload and new_field intermediary:
+    #   https://github.com/python/typeshed/pull/5823
+    new_field: dataclasses.Field[object] = dataclasses.field(**kw, metadata=meta)  # type: ignore[call-overload]
+    return new_field
+
+
+# These overloads lie about their return type just as both attrs and dataclasses
+# do so as to support the normal usage of `attribute: int = field()`
+@t.overload
+def ib(
+    marshmallow_field: marshmallow.fields.Field,
+    *,
+    default: t.Union[T, t.Callable[[], T]],
+    metadata: t.Optional[t.Mapping[object, object]] = None,
+    **kw: object,
+) -> T:
+    ...
+
+
+@t.overload
+def ib(
+    marshmallow_field: marshmallow.fields.Field,
+    *,
+    factory: t.Callable[[], T],
+    metadata: t.Optional[t.Mapping[object, object]] = None,
+    **kw: object,
+) -> T:
+    ...
+
+
+@t.overload
+def ib(
+    marshmallow_field: marshmallow.fields.Field,
+    *,
+    metadata: t.Optional[t.Mapping[object, object]] = None,
+    **kw: object,
+) -> object:
+    ...
+
+
+# The return type hint of object is certainly a lie but fits a lot better with
+# the normal use of `x: int = desert.ib()`.  Both dataclasses and attrs
+# prioritize hinting for this usage as well.  Perhaps someday we'll have a
+# plugin that indicates the actual type.
+def ib(
+    marshmallow_field: marshmallow.fields.Field,
+    metadata: t.Optional[t.Mapping[object, object]] = None,
+    **kw: object,
+) -> object:
     """Specify a marshmallow field in the metadata for an ``attr.dataclass``.
 
     .. code-block:: python
@@ -82,9 +177,13 @@ def ib(marshmallow_field: marshmallow.fields.Field, **kw) -> attr._make._Countin
         class A:
             x: int = desert.ib(marshmallow.fields.Int())
     """
-    meta = metadata(marshmallow_field)
-    meta.update(kw.pop("metadata", {}))
-    return attr.ib(**kw, metadata=meta)
+    if metadata is None:
+        metadata = {}
+
+    meta: t.Dict[object, object] = create_metadata(marshmallow_field)
+    meta.update(metadata)
+    new_field: attr._make._CountingAttr = attr.ib(**kw, metadata=meta)  # type: ignore[call-overload]
+    return new_field
 
 
 __version__ = desert._version.__version__

src/desert/_make.py

@@ -97,7 +97,9 @@ def class_schema(
     ``marshmallow_field`` key in the metadata dictionary.
     """
 
-    fields: t.Union[t.Tuple[dataclasses.Field, ...], t.Tuple[attr.Attribute, ...]]
+    fields: t.Union[
+        t.Tuple[dataclasses.Field[object], ...], t.Tuple[attr.Attribute[object], ...]
+    ]
 
     if not isinstance(clazz, type):
         raise desert.exceptions.UnknownType(
@@ -161,7 +163,7 @@ def class_schema(
 class VariadicTuple(marshmallow.fields.List):
     """Homogenous tuple with variable number of entries."""
 
-    def _deserialize(self, *args, **kwargs):
+    def _deserialize(self, *args: object, **kwargs: object) -> t.Tuple[object, ...]:  # type: ignore[override]
         return tuple(super()._deserialize(*args, **kwargs))
 
 
@@ -172,7 +174,9 @@ def only(items: t.Iterable[T]) -> T:
 
 
 def field_for_schema(
-    typ: type, default=marshmallow.missing, metadata: t.Mapping[t.Any, t.Any] = None
+    typ: type,
+    default: object = marshmallow.missing,
+    metadata: t.Optional[t.Mapping[t.Any, t.Any]] = None,
 ) -> marshmallow.fields.Field:
     """
     Get a marshmallow Field corresponding to the given python type.
@@ -221,7 +225,9 @@ def field_for_schema(
     field = None
 
     # If the field was already defined by the user
-    predefined_field = desert_metadata.get("marshmallow_field")
+    predefined_field = t.cast(
+        marshmallow.fields.Field, desert_metadata.get("marshmallow_field")
+    )
 
     if predefined_field:
         field = predefined_field
@@ -242,7 +248,7 @@ def field_for_schema(
             field = marshmallow.fields.List(field_for_schema(arguments[0]))
 
         if origin in (tuple, t.Tuple) and Ellipsis not in arguments:
-            field = marshmallow.fields.Tuple(
+            field = marshmallow.fields.Tuple(  # type: ignore[no-untyped-call]
                 tuple(field_for_schema(arg) for arg in arguments)
             )
         elif origin in (tuple, t.Tuple) and Ellipsis in arguments:
@@ -307,21 +313,24 @@ def field_for_schema(
 def _base_schema(clazz: type) -> t.Type[marshmallow.Schema]:
     class BaseSchema(marshmallow.Schema):
         @marshmallow.post_load
-        def make_data_class(self, data, **_):
+        def make_data_class(self, data: t.Mapping[str, object], **_: object) -> object:
             return clazz(**data)
 
     return BaseSchema
 
 
-def _get_field_default(field: t.Union[dataclasses.Field, attr.Attribute]):
+def _get_field_default(
+    field: t.Union[dataclasses.Field[object], "attr.Attribute[object]"],
+) -> object:
     """
     Return a marshmallow default value given a dataclass default value
     >>> _get_field_default(dataclasses.field())
     <marshmallow.missing>
     """
     if isinstance(field, dataclasses.Field):
-        # https://github.com/python/mypy/issues/10750
-        if field.default_factory != dataclasses.MISSING:  # type: ignore[misc]
+        # misc: https://github.com/python/mypy/issues/10750
+        # comparison-overlap: https://github.com/python/typeshed/pull/5900
+        if field.default_factory != dataclasses.MISSING:  # type: ignore[misc,comparison-overlap]
             return dataclasses.MISSING
         if field.default is dataclasses.MISSING:
             return marshmallow.missing
@@ -333,9 +342,9 @@ def _get_field_default(field: t.Union[dataclasses.Field, attr.Attribute]):
             # attrs specifically doesn't support this so as to support the
             # primary use case.
             # https://github.com/python-attrs/attrs/blob/38580632ceac1cd6e477db71e1d190a4130beed4/src/attr/__init__.pyi#L63-L65
-            if field.default.takes_self:  # type: ignore[union-attr]
+            if field.default.takes_self:  # type: ignore[attr-defined]
                 return attr.NOTHING
-            return field.default.factory  # type: ignore[union-attr]
+            return field.default.factory  # type: ignore[attr-defined]
         return field.default
     else:
         raise TypeError(field)