Validate ids

CHANGELOG.md

@@ -26,6 +26,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - `SelectionList` option IDs are usable as soon as the widget is instantiated https://github.com/Textualize/textual/issues/3903
 - Fix issue with `Strip.crop` when crop window start aligned with strip end https://github.com/Textualize/textual/pull/3998
 - Fixed Strip.crop_extend https://github.com/Textualize/textual/pull/4011
+- ID and class validation was too lenient https://github.com/Textualize/textual/issues/3954
 
 
 ## [0.47.1] - 2023-01-05

src/textual/dom.py

@@ -62,7 +62,7 @@
 
 from typing_extensions import Literal
 
-_re_identifier = re.compile(IDENTIFIER)
+_re_identifier = re.compile(f"^{IDENTIFIER}$")
 
 
 WalkMethod: TypeAlias = Literal["depth", "breadth"]

tests/test_dom.py

@@ -259,3 +259,24 @@ def test_walk_children_with_self_breadth(search):
     ]
 
     assert children == ["f", "e", "d", "c", "b", "a"]
+
+
+@pytest.mark.parametrize(
+    "identifier",
+    [
+        " bad",
+        "  terrible  ",
+        "worse!  ",
+        "&ampersand",
+        "amper&sand",
+        "ampersand&",
+        "2_leading_digits",
+        "água",  # water
+        "cão",  # dog
+        "@'/.23",
+    ],
+)
+def test_id_validation(identifier: str):
+    """Regression tests for https://github.com/Textualize/textual/issues/3954."""
+    with pytest.raises(BadIdentifier):
+        DOMNode(id=identifier)