Invalid pseudo selectors

src/textual/css/constants.py

@@ -61,6 +61,14 @@
     "underline",
     "uu",
 }
+VALID_PSEUDO_CLASSES: Final = {
+    "blur",
+    "disabled",
+    "enabled",
+    "focus-within",
+    "focus",
+    "hover",
+}
 
 
 NULL_SPACING: Final = Spacing.all(0)

src/textual/css/tokenizer.py

@@ -12,7 +12,9 @@
 from rich.syntax import Syntax
 from rich.text import Text
 
+from ..suggestions import get_suggestion
 from ._error_tools import friendly_list
+from .constants import VALID_PSEUDO_CLASSES
 
 
 class TokenError(Exception):
@@ -56,7 +58,7 @@ def _get_snippet(self) -> Panel:
             line_numbers=True,
             indent_guides=True,
             line_range=(max(0, line_no - 2), line_no + 2),
-            highlight_lines={line_no},
+            highlight_lines={line_no + 1},
         )
         syntax.stylize_range("reverse bold", self.start, self.end)
         return Panel(syntax, border_style="red")
@@ -227,6 +229,29 @@ def get_token(self, expect: Expect) -> Token:
             (line_no, col_no),
             referenced_by=None,
         )
+
+        if (
+            token.name == "pseudo_class"
+            and token.value.strip(":") not in VALID_PSEUDO_CLASSES
+        ):
+            pseudo_class = token.value.strip(":")
+            suggestion = get_suggestion(pseudo_class, list(VALID_PSEUDO_CLASSES))
+            all_valid = f"must be one of {friendly_list(VALID_PSEUDO_CLASSES)}"
+            if suggestion:
+                raise TokenError(
+                    self.path,
+                    self.code,
+                    (line_no, col_no),
+                    f"unknown pseudo-class {pseudo_class!r}; did you mean {suggestion!r}?; {all_valid}",
+                )
+            else:
+                raise TokenError(
+                    self.path,
+                    self.code,
+                    (line_no, col_no),
+                    f"unknown pseudo-class {pseudo_class!r}; {all_valid}",
+                )
+
         col_no += len(value)
         if col_no >= len(line):
             line_no += 1

tests/css/test_mega_stylesheet.css

@@ -140,52 +140,52 @@ A1
 
 /**********************************************************************/
 
-A:foo {}
-A:foo:bar {}
+A:focus {}
+A:focus:hover {}
 A
-:foo {}
+:focus {}
 A
-:foo:bar {}
+:focus:hover {}
 A
-:foo
-:bar {}
-A:foo-bar {}
+:focus
+:hover {}
+A:enabled {}
 A
-:foo-bar {}
+:enabled {}
 
-A :foo {}
-A :foo :bar {}
-A :foo-bar {}
+A :focus {}
+A :focus :hover {}
+A :enabled {}
 
-.A:foo {}
-.A:foo:bar {}
+.A:focus {}
+.A:focus:hover {}
 .A
-:foo {}
+:focus {}
 .A
-:foo:bar {}
+:focus:hover {}
 .A
-:foo
-:bar {}
-.A:foo-bar {}
+:focus
+:hover {}
+.A:enabled {}
 .A
-:foo-bar {}
+:enabled {}
 
-#A:foo {}
-#A:foo:bar {}
+#A:focus {}
+#A:focus:hover {}
 #A
-:foo {}
+:focus {}
 #A
-:foo:bar {}
+:focus:hover {}
 #A
-:foo
-:bar {}
-#A:foo-bar {}
+:focus
+:hover {}
+#A:enabled {}
 #A
-:foo-bar {}
+:enabled {}
 
-A1.A1.A1:foo {}
-A1.A1#A1:foo {}
-A1:foo.A1:foo#A1:foo {}
+A1.A1.A1:focus {}
+A1.A1#A1:focus {}
+A1:focus.A1:focus#A1:focus {}
 
 /**********************************************************************/
 

tests/css/test_parse.py

@@ -1226,3 +1226,21 @@ def test_combined_type_starts_with_number(self):
             stylesheet.add_source(f"StartType {separator} 1TestType {{}}")
             with pytest.raises(TokenError):
                 stylesheet.parse()
+
+
+def test_parse_bad_psuedo_selector():
+    """Check unknown selector raises a token error."""
+
+    bad_selector = """\
+Widget:foo{
+    border: red;
+}
+    """
+
+    stylesheet = Stylesheet()
+    stylesheet.add_source(bad_selector, "foo")
+
+    with pytest.raises(TokenError) as error:
+        stylesheet.parse()
+
+    assert error.value.start == (0, 6)