deprecate __version__ attribute

CHANGES.rst

@@ -1,4 +1,4 @@
-Version 2.2.0
+Version 3.0.0
 -------------
 
 Unreleased
@@ -16,6 +16,8 @@ Unreleased
     argument. These methods are conceptually linked to search methods such as
     ``in``, ``find``, and ``index``, which already do not escape their argument.
     :issue:`401`
+-   The ``__version__`` attribute is deprecated. Use feature detection, or
+    ``importlib.metadata.version("markupsafe")``, instead. :pr:`402`
 
 
 Version 2.1.3

pyproject.toml

@@ -1,5 +1,6 @@
 [project]
 name = "MarkupSafe"
+version = "3.0.0.dev"
 description = "Safely add untrusted strings to HTML/XML markup."
 readme = "README.rst"
 license = {text = "BSD-3-Clause"}
@@ -15,7 +16,6 @@ classifiers = [
     "Topic :: Text Processing :: Markup :: HTML",
 ]
 requires-python = ">=3.8"
-dynamic = ["version"]
 
 [project.urls]
 Donate = "https://palletsprojects.com/donate"

src/markupsafe/__init__.py

@@ -18,8 +18,6 @@ def __call__(self, s: t.Any, /) -> Markup:
             ...
 
 
-__version__ = "2.2.0.dev"
-
 _strip_comments_re = re.compile(r"<!--.*?-->", re.DOTALL)
 _strip_tags_re = re.compile(r"<.*?>", re.DOTALL)
 
@@ -315,3 +313,19 @@ def __float__(self, /) -> float:
     from ._native import escape as escape
     from ._native import escape_silent as escape_silent  # noqa: F401
     from ._native import soft_str as soft_str  # noqa: F401
+
+
+def __getattr__(name: str) -> t.Any:
+    if name == "__version__":
+        import importlib.metadata
+        import warnings
+
+        warnings.warn(
+            "The '__version__' attribute is deprecated and will be removed in"
+            " MarkupSafe 3.1. Use feature detection, or"
+            ' `importlib.metadata.version("markupsafe")`, instead.',
+            stacklevel=2,
+        )
+        return importlib.metadata.version("flask-classful")
+
+    raise AttributeError(name)