LibIDL: Begin parsing IDL namespaces

For example, the CSS namespace is defined via IDL, but we currently have
a manual implementation.

Userland/Libraries/LibIDL/IDLParser.cpp

@@ -599,6 +599,33 @@ void Parser::parse_interface(Interface& interface)
     consume_whitespace();
 }
 
+void Parser::parse_namespace(Interface& interface)
+{
+    consume_whitespace();
+
+    interface.name = lexer.consume_until([](auto ch) { return is_ascii_space(ch); });
+    interface.is_namespace = true;
+
+    consume_whitespace();
+    assert_specific('{');
+
+    for (;;) {
+        consume_whitespace();
+
+        if (lexer.consume_specific('}')) {
+            consume_whitespace();
+            assert_specific(';');
+            break;
+        }
+
+        HashMap<DeprecatedString, DeprecatedString> extended_attributes;
+        parse_function(extended_attributes, interface);
+    }
+
+    interface.namespace_class = DeprecatedString::formatted("{}Namespace", interface.name);
+    consume_whitespace();
+}
+
 void Parser::parse_enumeration(Interface& interface)
 {
     assert_string("enum"sv);
@@ -802,7 +829,7 @@ void Parser::parse_non_interface_entities(bool allow_interface, Interface& inter
             parse_interface_mixin(interface);
         } else if (lexer.next_is("callback")) {
             parse_callback_function(extended_attributes, interface);
-        } else if ((allow_interface && !lexer.next_is("interface")) || !allow_interface) {
+        } else if ((allow_interface && !lexer.next_is("interface") && !lexer.next_is("namespace")) || !allow_interface) {
             auto current_offset = lexer.tell();
             auto name = lexer.consume_until([](auto ch) { return is_ascii_space(ch); });
             consume_whitespace();
@@ -920,6 +947,8 @@ Interface& Parser::parse()
 
     if (lexer.consume_specific("interface"))
         parse_interface(interface);
+    else if (lexer.consume_specific("namespace"))
+        parse_namespace(interface);
 
     parse_non_interface_entities(false, interface);
 

Userland/Libraries/LibIDL/IDLParser.h

@@ -40,6 +40,7 @@ private:
     HashMap<DeprecatedString, DeprecatedString> parse_extended_attributes();
     void parse_attribute(HashMap<DeprecatedString, DeprecatedString>& extended_attributes, Interface&);
     void parse_interface(Interface&);
+    void parse_namespace(Interface&);
     void parse_non_interface_entities(bool allow_interface, Interface&);
     void parse_enumeration(Interface&);
     void parse_typedef(Interface&);

Userland/Libraries/LibIDL/Types.h

@@ -256,6 +256,7 @@ public:
     DeprecatedString name;
     DeprecatedString parent_name;
 
+    bool is_namespace { false };
     bool is_mixin { false };
 
     HashMap<DeprecatedString, DeprecatedString> extended_attributes;
@@ -291,6 +292,7 @@ public:
     DeprecatedString constructor_class;
     DeprecatedString prototype_class;
     DeprecatedString prototype_base_class;
+    DeprecatedString namespace_class;
     DeprecatedString global_mixin_class;
     HashMap<DeprecatedString, HashTable<DeprecatedString>> included_mixins;