Raise error for whitespace in class shorthand (e.g. ".a b") (#153)

* Minor fixes in streaming docs

* Test to assert result with '.a b'

* Raise error for whitespace in class shorthand

See discussion in #152.

Author: StabbarN

src/htpy/_attributes.py

@@ -57,6 +57,12 @@ def id_class_names_from_css_str(x: t.Any) -> Mapping[str, Attribute]:
     ids = [part.removeprefix("#").strip() for part in parts if part.startswith("#")]
     classes = [part.strip() for part in parts if not part.startswith("#") if part]
 
+    for class_ in classes:
+        if any(ch.isspace() for ch in class_):
+            raise ValueError(
+                "Whitespace is not allowed in class shorthand (use '.a.b' instead of '.a b')."
+            )
+
     assert len(ids) in (0, 1)
 
     result: dict[str, Attribute] = {}

tests/test_attributes.py

@@ -181,6 +181,14 @@ def test_id_class_wrong_order() -> None:
         div(".myclass#myid")
 
 
+def test_bad_classes_delimited_with_space() -> None:
+    with pytest.raises(
+        ValueError,
+        match=r"Whitespace is not allowed in class shorthand \(use '.a.b' instead of '.a b'\).",
+    ):
+        div(".a b")
+
+
 def test_id_class_bad_format() -> None:
     with pytest.raises(ValueError, match="id/class strings must start with # or ."):
         div("foo")