LibWeb: Reject non-exclusive none in text-decoration-line

Calme1709 · gmta · commit d6bb247bf725 · 2025-11-13T10:15:02.000+01:00
This updates the `parse_text_decoration_line_value` to reject values
which non-exclusively include `none` e.g. `underline none`.

It also simplifies handling by always producing a Vector (except for
`none`) and adding VERIFY_NOT_REACHED in more places which shouldn't be
reachable.
diff --git a/Libraries/LibWeb/CSS/ComputedProperties.cpp b/Libraries/LibWeb/CSS/ComputedProperties.cpp
@@ -1225,6 +1225,9 @@ Vector<TextDecorationLine> ComputedProperties::text_decoration_line() const
 {
     auto const& value = property(PropertyID::TextDecorationLine);
 
+    if (value.to_keyword() == Keyword::None)
+        return {};
+
     if (value.is_value_list()) {
         Vector<TextDecorationLine> lines;
         auto& values = value.as_value_list().values();
@@ -1234,14 +1237,7 @@ Vector<TextDecorationLine> ComputedProperties::text_decoration_line() const
         return lines;
     }
 
-    if (value.is_keyword()) {
-        if (value.to_keyword() == Keyword::None)
-            return {};
-        return { keyword_to_text_decoration_line(value.to_keyword()).release_value() };
-    }
-
-    dbgln("FIXME: Unsupported value for text-decoration-line: {}", value.to_string(SerializationMode::Normal));
-    return {};
+    VERIFY_NOT_REACHED();
 }
 
 TextDecorationStyle ComputedProperties::text_decoration_style() const
diff --git a/Libraries/LibWeb/CSS/Parser/PropertyParsing.cpp b/Libraries/LibWeb/CSS/Parser/PropertyParsing.cpp
@@ -4691,7 +4691,7 @@ RefPtr<StyleValue const> Parser::parse_text_decoration_line_value(TokenStream<Co
         if (auto maybe_line = keyword_to_text_decoration_line(value->to_keyword()); maybe_line.has_value()) {
             if (maybe_line == TextDecorationLine::None) {
                 if (!style_values.is_empty())
-                    break;
+                    return nullptr;
                 return value;
             }
             if (first_is_one_of(*maybe_line, TextDecorationLine::SpellingError, TextDecorationLine::GrammarError)) {
@@ -4703,7 +4703,7 @@ RefPtr<StyleValue const> Parser::parse_text_decoration_line_value(TokenStream<Co
             continue;
         }
 
-        break;
+        VERIFY_NOT_REACHED();
     }
 
     if (style_values.is_empty())
@@ -4713,9 +4713,6 @@ RefPtr<StyleValue const> Parser::parse_text_decoration_line_value(TokenStream<Co
     if (style_values.size() > 1 && includes_spelling_or_grammar_error_value)
         return nullptr;
 
-    if (style_values.size() == 1)
-        return *style_values.first();
-
     quick_sort(style_values, [](auto& left, auto& right) {
         return *keyword_to_text_decoration_line(left->to_keyword()) < *keyword_to_text_decoration_line(right->to_keyword());
     });
diff --git a/Tests/LibWeb/Text/expected/css/text-decoration-line-none.txt b/Tests/LibWeb/Text/expected/css/text-decoration-line-none.txt
@@ -0,0 +1 @@
+#foo { }
diff --git a/Tests/LibWeb/Text/input/css/text-decoration-line-none.html b/Tests/LibWeb/Text/input/css/text-decoration-line-none.html
@@ -0,0 +1,13 @@
+<!DOCTYPE html>
+
+<style>
+    #foo {
+        text-decoration-line: underline none;
+    }
+</style>
+<script src="../include.js"></script>
+<script>
+    test(() => {
+        println(document.styleSheets[0].cssRules[0].cssText);
+    });
+</script>
