LibWeb: Serialize text-decoration closer to spec

This gets us 32 WPT subtest passes that I'm aware of. :^)

Libraries/LibWeb/CSS/StyleValues/ShorthandStyleValue.cpp

@@ -233,8 +233,29 @@ String ShorthandStyleValue::to_string() const
             return align_self;
         return MUST(String::formatted("{} {}", align_self, justify_self));
     }
-    case PropertyID::TextDecoration:
-        return MUST(String::formatted("{} {} {} {}", longhand(PropertyID::TextDecorationLine)->to_string(), longhand(PropertyID::TextDecorationThickness)->to_string(), longhand(PropertyID::TextDecorationStyle)->to_string(), longhand(PropertyID::TextDecorationColor)->to_string()));
+    case PropertyID::TextDecoration: {
+        // The rule here seems to be, only print what's different from the default value,
+        // but if they're all default, print the line.
+        StringBuilder builder;
+        auto append_if_non_default = [&](PropertyID property_id) {
+            auto value = longhand(property_id);
+            if (!value->equals(property_initial_value({}, property_id))) {
+                if (!builder.is_empty())
+                    builder.append(' ');
+                builder.append(value->to_string());
+            }
+        };
+
+        append_if_non_default(PropertyID::TextDecorationLine);
+        append_if_non_default(PropertyID::TextDecorationThickness);
+        append_if_non_default(PropertyID::TextDecorationStyle);
+        append_if_non_default(PropertyID::TextDecorationColor);
+
+        if (builder.is_empty())
+            return longhand(PropertyID::TextDecorationLine)->to_string();
+
+        return builder.to_string_without_validation();
+    }
     default:
         StringBuilder builder;
         auto first = true;

Tests/LibWeb/Text/expected/css/CSSStyleDeclaration-all-supported-properties-and-default-values.txt

@@ -518,8 +518,8 @@ All supported properties and their default values exposed from CSSStyleDeclarati
 'text-align': 'start'
 'textAnchor': 'start'
 'text-anchor': 'start'
-'textDecoration': 'none auto solid rgb(0, 0, 0)'
-'text-decoration': 'none auto solid rgb(0, 0, 0)'
+'textDecoration': 'rgb(0, 0, 0)'
+'text-decoration': 'rgb(0, 0, 0)'
 'textDecorationColor': 'rgb(0, 0, 0)'
 'text-decoration-color': 'rgb(0, 0, 0)'
 'textDecorationLine': 'none'

Tests/LibWeb/Text/expected/wpt-import/css/css-text-decor/parsing/text-decoration-computed.txt

@@ -6,17 +6,17 @@ Rerun
 
 Found 12 tests
 
-12 Fail
+12 Pass
 Details
-Result	Test Name	MessageFail	Property text-decoration value 'none'	
-Fail	Property text-decoration value 'line-through'	
-Fail	Property text-decoration value 'solid'	
-Fail	Property text-decoration value 'currentcolor'	
-Fail	Property text-decoration value 'double overline underline'	
-Fail	Property text-decoration value 'underline overline line-through red'	
-Fail	Property text-decoration value 'rgba(10, 20, 30, 0.4) dotted'	
-Fail	Property text-decoration value 'underline dashed rgb(0, 255, 0)'	
-Fail	Property text-decoration value 'auto'	
-Fail	Property text-decoration value 'from-font'	
-Fail	Property text-decoration value '10px'	
-Fail	Property text-decoration value 'underline red from-font'	
+Result	Test Name	MessagePass	Property text-decoration value 'none'	
+Pass	Property text-decoration value 'line-through'	
+Pass	Property text-decoration value 'solid'	
+Pass	Property text-decoration value 'currentcolor'	
+Pass	Property text-decoration value 'double overline underline'	
+Pass	Property text-decoration value 'underline overline line-through red'	
+Pass	Property text-decoration value 'rgba(10, 20, 30, 0.4) dotted'	
+Pass	Property text-decoration value 'underline dashed rgb(0, 255, 0)'	
+Pass	Property text-decoration value 'auto'	
+Pass	Property text-decoration value 'from-font'	
+Pass	Property text-decoration value '10px'	
+Pass	Property text-decoration value 'underline red from-font'	

Tests/LibWeb/Text/expected/wpt-import/css/css-text-decor/parsing/text-decoration-valid.txt

@@ -6,20 +6,20 @@ Rerun
 
 Found 15 tests
 
-15 Fail
+15 Pass
 Details
-Result	Test Name	MessageFail	e.style['text-decoration'] = "none" should set the property value	
-Fail	e.style['text-decoration'] = "line-through" should set the property value	
-Fail	e.style['text-decoration'] = "solid" should set the property value	
-Fail	e.style['text-decoration'] = "currentcolor" should set the property value	
-Fail	e.style['text-decoration'] = "auto" should set the property value	
-Fail	e.style['text-decoration'] = "from-font" should set the property value	
-Fail	e.style['text-decoration'] = "10px" should set the property value	
-Fail	e.style['text-decoration'] = "double overline underline" should set the property value	
-Fail	e.style['text-decoration'] = "underline overline line-through red" should set the property value	
-Fail	e.style['text-decoration'] = "rgba(10, 20, 30, 0.4) dotted" should set the property value	
-Fail	e.style['text-decoration'] = "overline green from-font" should set the property value	
-Fail	e.style['text-decoration'] = "underline dashed green" should set the property value	
-Fail	e.style['text-decoration'] = "underline auto" should set the property value	
-Fail	e.style['text-decoration'] = "line-through 20px" should set the property value	
-Fail	e.style['text-decoration'] = "overline 3em" should set the property value	
+Result	Test Name	MessagePass	e.style['text-decoration'] = "none" should set the property value	
+Pass	e.style['text-decoration'] = "line-through" should set the property value	
+Pass	e.style['text-decoration'] = "solid" should set the property value	
+Pass	e.style['text-decoration'] = "currentcolor" should set the property value	
+Pass	e.style['text-decoration'] = "auto" should set the property value	
+Pass	e.style['text-decoration'] = "from-font" should set the property value	
+Pass	e.style['text-decoration'] = "10px" should set the property value	
+Pass	e.style['text-decoration'] = "double overline underline" should set the property value	
+Pass	e.style['text-decoration'] = "underline overline line-through red" should set the property value	
+Pass	e.style['text-decoration'] = "rgba(10, 20, 30, 0.4) dotted" should set the property value	
+Pass	e.style['text-decoration'] = "overline green from-font" should set the property value	
+Pass	e.style['text-decoration'] = "underline dashed green" should set the property value	
+Pass	e.style['text-decoration'] = "underline auto" should set the property value	
+Pass	e.style['text-decoration'] = "line-through 20px" should set the property value	
+Pass	e.style['text-decoration'] = "overline 3em" should set the property value	

Tests/LibWeb/Text/expected/wpt-import/css/cssom/serialize-values.txt

@@ -6,8 +6,8 @@ Rerun
 
 Found 687 tests
 
-473 Pass
-214 Fail
+478 Pass
+209 Fail
 Details
 Result	Test Name	MessagePass	background-attachment: scroll	
 Pass	background-attachment: fixed	
@@ -625,11 +625,11 @@ Pass	text-align: right
 Pass	text-align: center	
 Pass	text-align: justify	
 Pass	text-align: inherit	
-Fail	text-decoration: none	
-Fail	text-decoration: underline	
-Fail	text-decoration: overline	
-Fail	text-decoration: line-through	
-Fail	text-decoration: blink	
+Pass	text-decoration: none	
+Pass	text-decoration: underline	
+Pass	text-decoration: overline	
+Pass	text-decoration: line-through	
+Pass	text-decoration: blink	
 Pass	text-decoration: inherit	
 Pass	text-indent: 0px	
 Pass	text-indent: 1px