LibWeb/CSS: Add custom-ident blacklists to Properties.json

These excluded values use a similar notation to the ranges for numeric
types: `![foo,bar,baz]` to exclude `foo`, `bar`, and `baz`.

Documentation/CSSGeneratedFiles.md

@@ -72,6 +72,7 @@ The `valid-types` array lists the names of CSS value types, as defined in the la
 [CSS Values and Units spec](https://www.w3.org/TR/css-values/), without the `<>` around them.
 For numeric types, we use the [bracketed range notation](https://www.w3.org/TR/css-values-4/#css-bracketed-range-notation),
 for example `width` can take any non-negative length, so it has `"length [0,∞]"` in its `valid-types` array.
+For `<custom-ident>`s, the excluded identifiers are placed within `![]`, for example `"custom-ident ![all,none]"`.
 
 ## Keywords.json
 

Libraries/LibWeb/CSS/Properties.json

@@ -247,7 +247,7 @@
     "initial": "none",
     "valid-types": [
       "string",
-      "custom-ident"
+      "custom-ident ![none]"
     ],
     "valid-identifiers": [
       "none"
@@ -880,7 +880,15 @@
     "affects-layout": false,
     "animation-type": "discrete",
     "inherited": true,
-    "initial": "normal"
+    "initial": "normal",
+    "valid-types": [
+      "custom-ident ![normal,light,dark,only]"
+    ],
+    "valid-identifiers": [
+      "normal",
+      "light",
+      "dark"
+    ]
   },
   "column-count": {
     "animation-type": "by-computed-value",
@@ -975,7 +983,7 @@
     "inherited": false,
     "initial": "none",
     "valid-types": [
-      "custom-ident",
+      "custom-ident ![none]",
       "integer [-∞,∞]"
     ],
     "valid-identifiers": [
@@ -987,7 +995,7 @@
     "inherited": false,
     "initial": "none",
     "valid-types": [
-      "custom-ident",
+      "custom-ident ![none]",
       "integer [-∞,∞]"
     ],
     "valid-identifiers": [
@@ -999,7 +1007,7 @@
     "inherited": false,
     "initial": "none",
     "valid-types": [
-      "custom-ident",
+      "custom-ident ![none]",
       "integer [-∞,∞]"
     ],
     "valid-identifiers": [
@@ -2841,7 +2849,7 @@
     "initial": "all",
     "valid-types": [
       "string",
-      "custom-ident"
+      "custom-ident ![all,none]"
     ],
     "valid-identifiers": [
       "all",
@@ -2902,7 +2910,7 @@
     "inherited": false,
     "initial": "none",
     "valid-types": [
-      "custom-ident"
+      "custom-ident ![auto,none]"
     ],
     "valid-identifiers": [
       "none"

Meta/Lagom/Tools/CodeGenerators/LibWeb/GenerateCSSPropertyID.cpp

@@ -250,6 +250,7 @@ enum class ValueType {
 bool property_accepts_type(PropertyID, ValueType);
 bool property_accepts_keyword(PropertyID, Keyword);
 Optional<ValueType> property_resolves_percentages_relative_to(PropertyID);
+Vector<StringView> property_custom_ident_blacklist(PropertyID);
 
 // These perform range-checking, but are also safe to call with properties that don't accept that type. (They'll just return false.)
 bool property_accepts_angle(PropertyID, Angle const&);
@@ -938,6 +939,53 @@ Optional<ValueType> property_resolves_percentages_relative_to(PropertyID propert
     }
 }
 
+Vector<StringView> property_custom_ident_blacklist(PropertyID property_id)
+{
+    switch (property_id) {
+)~~~");
+
+    properties.for_each_member([&](auto& name, auto& value) {
+        VERIFY(value.is_object());
+        auto& object = value.as_object();
+        if (is_legacy_alias(object))
+            return;
+
+        // We only have a custom-ident blacklist if we accept custom idents!
+        if (auto maybe_valid_types = object.get_array("valid-types"sv); maybe_valid_types.has_value() && !maybe_valid_types->is_empty()) {
+            auto& valid_types = maybe_valid_types.value();
+            for (auto const& valid_type : valid_types.values()) {
+                auto type_and_parameters = MUST(valid_type.as_string().split(' '));
+                if (type_and_parameters.first() != "custom-ident"sv || type_and_parameters.size() == 1)
+                    continue;
+                VERIFY(type_and_parameters.size() == 2);
+
+                auto parameters_string = type_and_parameters[1].bytes_as_string_view();
+                VERIFY(parameters_string.starts_with("!["sv) && parameters_string.ends_with(']'));
+                auto blacklisted_keywords = parameters_string.substring_view(2, parameters_string.length() - 3).split_view(',');
+
+                auto property_generator = generator.fork();
+                property_generator.set("property_name:titlecase", title_casify(name));
+                property_generator.append(R"~~~(
+    case PropertyID::@property_name:titlecase@:
+        return Vector { )~~~");
+                for (auto const& keyword : blacklisted_keywords) {
+                    auto value_generator = property_generator.fork();
+                    value_generator.set("keyword", keyword);
+
+                    value_generator.append("\"@keyword@\"sv, ");
+                }
+
+                property_generator.appendln("};");
+            }
+        }
+    });
+
+    generator.append(R"~~~(
+    default:
+        return {};
+    }
+}
+
 size_t property_maximum_value_count(PropertyID property_id)
 {
     switch (property_id) {