Type hint schemapi.py

altair/utils/schemapi.py

@@ -4,6 +4,7 @@
 import contextlib
 import inspect
 import json
+import sys
 import textwrap
 from typing import (
     Any,
@@ -15,6 +16,11 @@
     Tuple,
     Iterable,
     Type,
+    Generator,
+    Union,
+    overload,
+    Literal,
+    TypeVar,
 )
 from itertools import zip_longest
 
@@ -26,6 +32,13 @@
 
 from altair import vegalite
 
+if sys.version_info >= (3, 11):
+    from typing import Self
+else:
+    from typing_extensions import Self
+
+_TSchemaBase = TypeVar("_TSchemaBase", bound="SchemaBase")
+
 ValidationErrorList = List[jsonschema.exceptions.ValidationError]
 GroupedValidationErrors = Dict[str, ValidationErrorList]
 
@@ -35,21 +48,21 @@
 # larger specs, but leads to much more useful tracebacks for the user.
 # Individual schema classes can override this by setting the
 # class-level _class_is_valid_at_instantiation attribute to False
-DEBUG_MODE = True
+DEBUG_MODE: bool = True
 
 
-def enable_debug_mode():
+def enable_debug_mode() -> None:
     global DEBUG_MODE
     DEBUG_MODE = True
 
 
-def disable_debug_mode():
+def disable_debug_mode() -> None:
     global DEBUG_MODE
     DEBUG_MODE = False
 
 
 @contextlib.contextmanager
-def debug_mode(arg):
+def debug_mode(arg: bool) -> Generator[None, None, None]:
     global DEBUG_MODE
     original = DEBUG_MODE
     DEBUG_MODE = arg
@@ -59,12 +72,35 @@ def debug_mode(arg):
         DEBUG_MODE = original
 
 
+@overload
 def validate_jsonschema(
     spec: Dict[str, Any],
     schema: Dict[str, Any],
-    rootschema: Optional[Dict[str, Any]] = None,
-    raise_error: bool = True,
+    rootschema: Optional[Dict[str, Any]] = ...,
+    *,
+    raise_error: Literal[True] = ...,
+) -> None:
+    ...
+
+
+@overload
+def validate_jsonschema(
+    spec: Dict[str, Any],
+    schema: Dict[str, Any],
+    rootschema: Optional[Dict[str, Any]] = ...,
+    *,
+    raise_error: Literal[False],
 ) -> Optional[jsonschema.exceptions.ValidationError]:
+    ...
+
+
+def validate_jsonschema(
+    spec,
+    schema,
+    rootschema=None,
+    *,
+    raise_error=True,
+):
     """Validates the passed in spec against the schema in the context of the
     rootschema. If any errors are found, they are deduplicated and prioritized
     and only the most relevant errors are kept. Errors are then either raised
@@ -85,7 +121,7 @@ def validate_jsonschema(
         # error message. Setting a new attribute like this is not ideal as
         # it then no longer matches the type ValidationError. It would be better
         # to refactor this function to never raise but only return errors.
-        main_error._all_errors = grouped_errors  # type: ignore[attr-defined]
+        main_error._all_errors = grouped_errors
         if raise_error:
             raise main_error
         else:
@@ -319,7 +355,7 @@ def _deduplicate_by_message(errors: ValidationErrorList) -> ValidationErrorList:
     return list({e.message: e for e in errors}.values())
 
 
-def _subclasses(cls):
+def _subclasses(cls: type) -> Generator[type, None, None]:
     """Breadth-first sequence of all classes which inherit from cls."""
     seen = set()
     current_set = {cls}
@@ -330,7 +366,7 @@ def _subclasses(cls):
             yield cls
 
 
-def _todict(obj, context):
+def _todict(obj: Any, context: Optional[Dict[str, Any]]) -> Any:
     """Convert an object to a dict representation."""
     if isinstance(obj, SchemaBase):
         return obj.to_dict(validate=False, context=context)
@@ -348,7 +384,7 @@ def _todict(obj, context):
         return obj
 
 
-def _resolve_references(schema, root=None):
+def _resolve_references(schema: dict, root: Optional[dict] = None) -> dict:
     """Resolve schema references."""
     resolver = jsonschema.RefResolver.from_schema(root or schema)
     while "$ref" in schema:
@@ -597,9 +633,9 @@ class SchemaBase:
 
     _schema: Optional[Dict[str, Any]] = None
     _rootschema: Optional[Dict[str, Any]] = None
-    _class_is_valid_at_instantiation = True
+    _class_is_valid_at_instantiation: bool = True
 
-    def __init__(self, *args, **kwds):
+    def __init__(self, *args: Any, **kwds: Any) -> None:
         # Two valid options for initialization, which should be handled by
         # derived classes:
         # - a single arg with no kwds, for, e.g. {'type': 'string'}
@@ -623,7 +659,9 @@ def __init__(self, *args, **kwds):
         if DEBUG_MODE and self._class_is_valid_at_instantiation:
             self.to_dict(validate=True)
 
-    def copy(self, deep=True, ignore=()):
+    def copy(
+        self, deep: Union[bool, Iterable] = True, ignore: Optional[list] = None
+    ) -> Self:
         """Return a copy of the object
 
         Parameters
@@ -648,7 +686,9 @@ def _shallow_copy(obj):
             else:
                 return obj
 
-        def _deep_copy(obj, ignore=()):
+        def _deep_copy(obj, ignore: Optional[list] = None):
+            if ignore is None:
+                ignore = []
             if isinstance(obj, SchemaBase):
                 args = tuple(_deep_copy(arg) for arg in obj._args)
                 kwds = {
@@ -668,7 +708,7 @@ def _deep_copy(obj, ignore=()):
                 return obj
 
         try:
-            deep = list(deep)
+            deep = list(deep)  # type: ignore[arg-type]
         except TypeError:
             deep_is_list = False
         else:
@@ -680,6 +720,8 @@ def _deep_copy(obj, ignore=()):
         with debug_mode(False):
             copy = self.__class__(*self._args, **self._kwds)
         if deep_is_list:
+            # Assert statement is for the benefit of Mypy
+            assert isinstance(deep, list)
             for attr in deep:
                 copy[attr] = _shallow_copy(copy._get(attr))
         return copy
@@ -873,12 +915,19 @@ def to_json(
         return json.dumps(dct, indent=indent, sort_keys=sort_keys, **kwargs)
 
     @classmethod
-    def _default_wrapper_classes(cls):
+    def _default_wrapper_classes(cls) -> Generator[Type["SchemaBase"], None, None]:
         """Return the set of classes used within cls.from_dict()"""
         return _subclasses(SchemaBase)
 
     @classmethod
-    def from_dict(cls, dct, validate=True, _wrapper_classes=None):
+    def from_dict(
+        cls,
+        dct: dict,
+        validate: bool = True,
+        _wrapper_classes: Optional[Iterable[Type["SchemaBase"]]] = None,
+        # Type hints for this method would get rather complicated
+        # if we want to provide a more specific return type
+    ) -> "SchemaBase":
         """Construct class from a dictionary representation
 
         Parameters
@@ -887,7 +936,7 @@ def from_dict(cls, dct, validate=True, _wrapper_classes=None):
             The dict from which to construct the class
         validate : boolean
             If True (default), then validate the input against the schema.
-        _wrapper_classes : list (optional)
+        _wrapper_classes : iterable (optional)
             The set of SchemaBase classes to use when constructing wrappers
             of the dict inputs. If not specified, the result of
             cls._default_wrapper_classes will be used.
@@ -910,7 +959,14 @@ def from_dict(cls, dct, validate=True, _wrapper_classes=None):
         return converter.from_dict(dct, cls)
 
     @classmethod
-    def from_json(cls, json_string, validate=True, **kwargs):
+    def from_json(
+        cls,
+        json_string: str,
+        validate: bool = True,
+        **kwargs: Any
+        # Type hints for this method would get rather complicated
+        # if we want to provide a more specific return type
+    ) -> Any:
         """Instantiate the object from a valid JSON string
 
         Parameters
@@ -931,27 +987,36 @@ def from_json(cls, json_string, validate=True, **kwargs):
         return cls.from_dict(dct, validate=validate)
 
     @classmethod
-    def validate(cls, instance, schema=None):
+    def validate(
+        cls, instance: Dict[str, Any], schema: Optional[Dict[str, Any]] = None
+    ) -> None:
         """
         Validate the instance against the class schema in the context of the
         rootschema.
         """
         if schema is None:
             schema = cls._schema
+        # For the benefit of mypy
+        assert schema is not None
         return validate_jsonschema(
             instance, schema, rootschema=cls._rootschema or cls._schema
         )
 
     @classmethod
-    def resolve_references(cls, schema=None):
+    def resolve_references(cls, schema: Optional[dict] = None) -> dict:
         """Resolve references in the context of this object's schema or root schema."""
+        schema_to_pass = schema or cls._schema
+        # For the benefit of mypy
+        assert schema_to_pass is not None
         return _resolve_references(
-            schema=(schema or cls._schema),
+            schema=schema_to_pass,
             root=(cls._rootschema or cls._schema or schema),
         )
 
     @classmethod
-    def validate_property(cls, name, value, schema=None):
+    def validate_property(
+        cls, name: str, value: Any, schema: Optional[dict] = None
+    ) -> None:
         """
         Validate a property against property schema in the context of the
         rootschema
@@ -962,8 +1027,8 @@ def validate_property(cls, name, value, schema=None):
             value, props.get(name, {}), rootschema=cls._rootschema or cls._schema
         )
 
-    def __dir__(self):
-        return sorted(super().__dir__() + list(self._kwds.keys()))
+    def __dir__(self) -> list:
+        return sorted(list(super().__dir__()) + list(self._kwds.keys()))
 
 
 def _passthrough(*args, **kwds):
@@ -980,7 +1045,7 @@ class _FromDict:
 
     _hash_exclude_keys = ("definitions", "title", "description", "$schema", "id")
 
-    def __init__(self, class_list):
+    def __init__(self, class_list: Iterable[Type[SchemaBase]]) -> None:
         # Create a mapping of a schema hash to a list of matching classes
         # This lets us quickly determine the correct class to construct
         self.class_dict = collections.defaultdict(list)
@@ -989,7 +1054,7 @@ def __init__(self, class_list):
                 self.class_dict[self.hash_schema(cls._schema)].append(cls)
 
     @classmethod
-    def hash_schema(cls, schema, use_json=True):
+    def hash_schema(cls, schema: dict, use_json: bool = True) -> int:
         """
         Compute a python hash for a nested dictionary which
         properly handles dicts, lists, sets, and tuples.
@@ -1025,14 +1090,29 @@ def _freeze(val):
             return hash(_freeze(schema))
 
     def from_dict(
-        self, dct, cls=None, schema=None, rootschema=None, default_class=_passthrough
-    ):
+        self,
+        dct: dict,
+        cls: Optional[Type[SchemaBase]] = None,
+        schema: Optional[dict] = None,
+        rootschema: Optional[dict] = None,
+        default_class=_passthrough,
+        # Type hints for this method would get rather complicated
+        # if we want to provide a more specific return type
+    ) -> Any:
         """Construct an object from a dict representation"""
         if (schema is None) == (cls is None):
             raise ValueError("Must provide either cls or schema, but not both.")
         if schema is None:
-            schema = schema or cls._schema
-            rootschema = rootschema or cls._rootschema
+            # Can ignore type errors as  cls is not None in case schema is
+            schema = cls._schema  # type: ignore[union-attr]
+            # For the benefit of mypy
+            assert schema is not None
+            if rootschema:
+                rootschema = rootschema
+            elif cls is not None and cls._rootschema is not None:
+                rootschema = cls._rootschema
+            else:
+                rootschema = None
         rootschema = rootschema or schema
 
         if isinstance(dct, SchemaBase):
@@ -1086,7 +1166,7 @@ def from_dict(
 
 
 class _PropertySetter:
-    def __init__(self, prop, schema):
+    def __init__(self, prop: str, schema: dict) -> None:
         self.prop = prop
         self.schema = schema
 
@@ -1133,7 +1213,7 @@ def __call__(self, *args, **kwargs):
         return obj
 
 
-def with_property_setters(cls):
+def with_property_setters(cls: _TSchemaBase) -> _TSchemaBase:
     """
     Decorator to add property setters to a Schema class.
     """

altair/vegalite/v5/api.py

@@ -2592,7 +2592,7 @@ def _get_name(cls):
         return f"view_{cls._counter}"
 
     @classmethod
-    def from_dict(cls, dct, validate=True) -> "Chart":  # type: ignore[override]  # Not the same signature as SchemaBase.from_dict. Would ideally be aligned in the future
+    def from_dict(cls, dct, validate=True) -> core.SchemaBase:  # type: ignore[override]  # Not the same signature as SchemaBase.from_dict. Would ideally be aligned in the future
         """Construct class from a dictionary representation
 
         Parameters