LibIDL: Also parse extended attributes after 'optional'

From the WebIDL grammar:
(https://webidl.spec.whatwg.org/#prod-Argument)

Argument ::
    ExtendedAttributeList ArgumentRest
ArgumentRest ::
    optional TypeWithExtendedAttributes ArgumentName Default
TypeWithExtendedAttributes ::
    ExtendedAttributeList Type

One IDL file has been updated to match the spec literally, as it can now
be parsed properly.

2 files changed, 7 insertions, 1 deletions

diff --git a/Userland/Libraries/LibIDL/IDLParser.cpp b/Userland/Libraries/LibIDL/IDLParser.cpp
index 7f12d0b313..87adc465bc 100644
--- a/Userland/Libraries/LibIDL/IDLParser.cpp
+++ b/Userland/Libraries/LibIDL/IDLParser.cpp
@@ -298,6 +298,12 @@ Vector<Parameter> Parser::parse_parameters()
         bool optional = lexer.consume_specific("optional");
         if (optional)
             consume_whitespace();
+        if (lexer.consume_specific('[')) {
+            // Not explicitly forbidden by the grammar but unlikely to happen in practice - if it does,
+            // we'll have to teach the parser how to merge two sets of extended attributes.
+            VERIFY(extended_attributes.is_empty());
+            extended_attributes = parse_extended_attributes();
+        }
         auto type = parse_type();
         bool variadic = lexer.consume_specific("..."sv);
         consume_whitespace();
diff --git a/Userland/Libraries/LibWeb/CSS/CSSStyleDeclaration.idl b/Userland/Libraries/LibWeb/CSS/CSSStyleDeclaration.idl
index 02dbc94f5e..725ca646bc 100644
--- a/Userland/Libraries/LibWeb/CSS/CSSStyleDeclaration.idl
+++ b/Userland/Libraries/LibWeb/CSS/CSSStyleDeclaration.idl
@@ -10,7 +10,7 @@ interface CSSStyleDeclaration {
     CSSOMString getPropertyValue(CSSOMString property);
     CSSOMString getPropertyPriority(CSSOMString property);
 
-    [CEReactions] undefined setProperty(CSSOMString property, [LegacyNullToEmptyString] CSSOMString value, [LegacyNullToEmptyString] optional CSSOMString priority = "");
+    [CEReactions] undefined setProperty(CSSOMString property, [LegacyNullToEmptyString] CSSOMString value, optional [LegacyNullToEmptyString] CSSOMString priority = "");
     [CEReactions] CSSOMString removeProperty(CSSOMString property);
 
 };