2025-12-01

2026-03-17 14:58:51 -06:00
parent 183e865f8b
commit 4b82b57113
6846 changed files with 954887 additions and 162606 deletions
@@ -0,0 +1,59 @@
+from typing import Any, Tuple, Union
+
+__all__ = [
+    "Description",
+    "is_description",
+    "register_description",
+    "unregister_description",
+]
+
+
+class Description:
+    """Type checker for human readable descriptions.
+
+    By default, only ordinary strings are accepted as descriptions,
+    but you can register() other classes that will also be allowed,
+    e.g. to support lazy string objects that are evaluated only at runtime.
+    If you register(object), any object will be allowed as description.
+    """
+
+    bases: Union[type, Tuple[type, ...]] = str
+
+    @classmethod
+    def isinstance(cls, obj: Any) -> bool:
+        return isinstance(obj, cls.bases)
+
+    @classmethod
+    def register(cls, base: type) -> None:
+        """Register a class that shall be accepted as a description."""
+        if not isinstance(base, type):
+            raise TypeError("Only types can be registered.")
+        if base is object:
+            cls.bases = object
+        elif cls.bases is object:
+            cls.bases = base
+        elif not isinstance(cls.bases, tuple):
+            if base is not cls.bases:
+                cls.bases = (cls.bases, base)
+        elif base not in cls.bases:
+            cls.bases += (base,)
+
+    @classmethod
+    def unregister(cls, base: type) -> None:
+        """Unregister a class that shall no more be accepted as a description."""
+        if not isinstance(base, type):
+            raise TypeError("Only types can be unregistered.")
+        if isinstance(cls.bases, tuple):
+            if base in cls.bases:  # pragma: no branch
+                cls.bases = tuple(b for b in cls.bases if b is not base)
+            if not cls.bases:
+                cls.bases = object
+            elif len(cls.bases) == 1:
+                cls.bases = cls.bases[0]
+        elif cls.bases is base:
+            cls.bases = object
+
+
+is_description = Description.isinstance
+register_description = Description.register
+unregister_description = Description.unregister