star

venv/lib/python3.9/site-packages/graphql/pyutils/undefined.py

@@ -0,0 +1,47 @@
+import warnings
+from typing import Any, Optional
+
+__all__ = ["Undefined", "UndefinedType"]
+
+
+class UndefinedType(ValueError):
+    """Auxiliary class for creating the Undefined singleton."""
+
+    _instance: Optional["UndefinedType"] = None
+
+    def __new__(cls) -> "UndefinedType":
+        if cls._instance is None:
+            cls._instance = super().__new__(cls)
+        else:
+            warnings.warn("Redefinition of 'Undefined'", RuntimeWarning, stacklevel=2)
+        return cls._instance
+
+    def __reduce__(self) -> str:
+        return "Undefined"
+
+    def __repr__(self) -> str:
+        return "Undefined"
+
+    __str__ = __repr__
+
+    def __hash__(self) -> int:
+        return hash(UndefinedType)
+
+    def __bool__(self) -> bool:
+        return False
+
+    def __eq__(self, other: Any) -> bool:
+        return other is Undefined
+
+    def __ne__(self, other: Any) -> bool:
+        return not self == other
+
+
+# Used to indicate undefined or invalid values (like "undefined" in JavaScript):
+Undefined = UndefinedType()
+
+Undefined.__doc__ = """Symbol for undefined values
+
+This singleton object is used to describe undefined or invalid  values.
+It can be used in places where you would use ``undefined`` in GraphQL.js.
+"""