add help message to vdom constructor

Author: rmorshea

src/idom/core/vdom.py

@@ -1,7 +1,9 @@
 from __future__ import annotations
 
 import logging
-from typing import Any, Mapping, cast
+from functools import wraps
+from typing import Any, Mapping, TypeVar, cast
+from warnings import warn
 
 from fastjsonschema import compile as compile_json_schema
 
@@ -128,6 +130,31 @@ def is_vdom(value: Any) -> bool:
     )
 
 
+_T = TypeVar("_T")
+
+
+def _help_message(func: _T) -> _T:
+    @wraps(func)
+    def wrapper(*args, **kwargs):
+        try:
+            return func(*args, **kwargs)
+        except TypeError:  # pragma: no cover
+            warn(
+                (
+                    "Element constructor signatures have changed! A CLI tool for "
+                    "automatically updating code to the latest API has been provided "
+                    "with this release of IDOM (e.g. 'idom update-html-usages'). For "
+                    "start a discussion if you need help transitioning to this new "
+                    "interface: https://github.com/idom-team/idom/discussions/new?category=question"
+                ),
+                UserWarning,
+            )
+            raise
+
+    return wrapper
+
+
+@_help_message
 def vdom(
     tag: str, *children: VdomChild, key: Key | None = None, **attributes: Any
 ) -> VdomDict: