1 files changed, 198 insertions, 0 deletions
diff --git a/jsonschema/_types.py b/jsonschema/_types.py
new file mode 100644
index 0000000..d142810
--- /dev/null
+++ b/jsonschema/_types.py
@@ -0,0 +1,198 @@
+from __future__ import annotations
+
+from typing import Any, Callable, Mapping
+import numbers
+
+from rpds import HashTrieMap
+import attr
+
+from jsonschema.exceptions import UndefinedTypeCheck
+
+
+# unfortunately, the type of HashTrieMap is generic, and if used as the attr.ib
+# converter, the generic type is presented to mypy, which then fails to match
+# the concrete type of a type checker mapping
+# this "do nothing" wrapper presents the correct information to mypy
+def _typed_map_converter(
+    init_val: Mapping[str, Callable[[TypeChecker, Any], bool]],
+) -> HashTrieMap[str, Callable[[TypeChecker, Any], bool]]:
+    return HashTrieMap.convert(init_val)
+
+
+def is_array(checker, instance):
+    return isinstance(instance, list)
+
+
+def is_bool(checker, instance):
+    return isinstance(instance, bool)
+
+
+def is_integer(checker, instance):
+    # bool inherits from int, so ensure bools aren't reported as ints
+    if isinstance(instance, bool):
+        return False
+    return isinstance(instance, int)
+
+
+def is_null(checker, instance):
+    return instance is None
+
+
+def is_number(checker, instance):
+    # bool inherits from int, so ensure bools aren't reported as ints
+    if isinstance(instance, bool):
+        return False
+    return isinstance(instance, numbers.Number)
+
+
+def is_object(checker, instance):
+    return isinstance(instance, dict)
+
+
+def is_string(checker, instance):
+    return isinstance(instance, str)
+
+
+def is_any(checker, instance):
+    return True
+
+
+@attr.s(frozen=True, repr=False)
+class TypeChecker:
+    """
+    A :kw:`type` property checker.
+
+    A `TypeChecker` performs type checking for a `Validator`, converting
+    between the defined JSON Schema types and some associated Python types or
+    objects.
+
+    Modifying the behavior just mentioned by redefining which Python objects
+    are considered to be of which JSON Schema types can be done using
+    `TypeChecker.redefine` or `TypeChecker.redefine_many`, and types can be
+    removed via `TypeChecker.remove`. Each of these return a new `TypeChecker`.
+
+    Arguments:
+
+        type_checkers:
+
+            The initial mapping of types to their checking functions.
+    """
+
+    _type_checkers: HashTrieMap[
+        str, Callable[[TypeChecker, Any], bool],
+    ] = attr.ib(
+        default=HashTrieMap(),
+        converter=_typed_map_converter,
+    )
+
+    def __repr__(self):
+        types = ", ".join(repr(k) for k in sorted(self._type_checkers))
+        return f"<{self.__class__.__name__} types={{{types}}}>"
+
+    def is_type(self, instance, type: str) -> bool:
+        """
+        Check if the instance is of the appropriate type.
+
+        Arguments:
+
+            instance:
+
+                The instance to check
+
+            type:
+
+                The name of the type that is expected.
+
+        Raises:
+
+            `jsonschema.exceptions.UndefinedTypeCheck`:
+
+                if ``type`` is unknown to this object.
+        """
+        try:
+            fn = self._type_checkers[type]
+        except KeyError:
+            raise UndefinedTypeCheck(type) from None
+
+        return fn(self, instance)
+
+    def redefine(self, type: str, fn) -> TypeChecker:
+        """
+        Produce a new checker with the given type redefined.
+
+        Arguments:
+
+            type:
+
+                The name of the type to check.
+
+            fn (collections.abc.Callable):
+
+                A callable taking exactly two parameters - the type
+                checker calling the function and the instance to check.
+                The function should return true if instance is of this
+                type and false otherwise.
+        """
+        return self.redefine_many({type: fn})
+
+    def redefine_many(self, definitions=()) -> TypeChecker:
+        """
+        Produce a new checker with the given types redefined.
+
+        Arguments:
+
+            definitions (dict):
+
+                A dictionary mapping types to their checking functions.
+        """
+        type_checkers = self._type_checkers.update(definitions)
+        return attr.evolve(self, type_checkers=type_checkers)
+
+    def remove(self, *types) -> TypeChecker:
+        """
+        Produce a new checker with the given types forgotten.
+
+        Arguments:
+
+            types:
+
+                the names of the types to remove.
+
+        Raises:
+
+            `jsonschema.exceptions.UndefinedTypeCheck`:
+
+                if any given type is unknown to this object
+        """
+        type_checkers = self._type_checkers
+        for each in types:
+            try:
+                type_checkers = type_checkers.remove(each)
+            except KeyError:
+                raise UndefinedTypeCheck(each)
+        return attr.evolve(self, type_checkers=type_checkers)
+
+
+draft3_type_checker = TypeChecker(
+    {
+        "any": is_any,
+        "array": is_array,
+        "boolean": is_bool,
+        "integer": is_integer,
+        "object": is_object,
+        "null": is_null,
+        "number": is_number,
+        "string": is_string,
+    },
+)
+draft4_type_checker = draft3_type_checker.remove("any")
+draft6_type_checker = draft4_type_checker.redefine(
+    "integer",
+    lambda checker, instance: (
+        is_integer(checker, instance)
+        or isinstance(instance, float) and instance.is_integer()
+    ),
+)
+draft7_type_checker = draft6_type_checker
+draft201909_type_checker = draft7_type_checker
+draft202012_type_checker = draft201909_type_checker