LibIDL: Support partial interfaces

Partial interfaces have the same name as the interface they extend, and
can appear in any order. In practice, we import the partial interfaces
into the main interface's IDL.

Libraries/LibIDL/IDLParser.cpp

@@ -813,6 +813,17 @@ void Parser::parse_interface(Interface& interface)
     consume_whitespace();
 }
 
+void Parser::parse_partial_interface(Interface& parent)
+{
+    assert_string("partial"sv);
+    consume_whitespace();
+    assert_string("interface"sv);
+
+    auto partial_interface = make<Interface>();
+    parse_interface(*partial_interface);
+    parent.partial_interfaces.append(move(partial_interface));
+}
+
 void Parser::parse_namespace(Interface& interface)
 {
     consume_whitespace();
@@ -1051,6 +1062,8 @@ void Parser::parse_non_interface_entities(bool allow_interface, Interface& inter
             parse_enumeration(extended_attributes, interface);
         } else if (lexer.next_is("typedef")) {
             parse_typedef(interface);
+        } else if (lexer.next_is("partial interface"sv)) {
+            parse_partial_interface(interface);
         } else if (lexer.next_is("interface mixin")) {
             parse_interface_mixin(interface);
         } else if (lexer.next_is("callback")) {
@@ -1183,6 +1196,11 @@ Interface& Parser::parse()
 
     for (auto& import : imports) {
         // FIXME: Instead of copying every imported entity into the current interface, query imports directly
+        for (auto& partial_interface : import.partial_interfaces) {
+            if (partial_interface->name == interface.name)
+                interface.extend_with_partial_interface(*partial_interface);
+        }
+
         for (auto& dictionary : import.dictionaries)
             interface.dictionaries.set(dictionary.key, dictionary.value);
 

Libraries/LibIDL/IDLParser.h

@@ -45,6 +45,7 @@ private:
     HashMap<ByteString, ByteString> parse_extended_attributes();
     void parse_attribute(HashMap<ByteString, ByteString>& extended_attributes, Interface&, IsStatic is_static = IsStatic::No);
     void parse_interface(Interface&);
+    void parse_partial_interface(Interface& parent);
     void parse_namespace(Interface&);
     void parse_non_interface_entities(bool allow_interface, Interface&);
     void parse_enumeration(HashMap<ByteString, ByteString>, Interface&);

Libraries/LibIDL/Types.cpp

@@ -305,4 +305,13 @@ void EffectiveOverloadSet::remove_all_other_entries()
     m_items = move(new_items);
 }
 
+void Interface::extend_with_partial_interface(Interface const& partial)
+{
+    attributes.extend(partial.attributes);
+    static_attributes.extend(partial.static_attributes);
+    constants.extend(partial.constants);
+    functions.extend(partial.functions);
+    static_functions.extend(partial.static_functions);
+}
+
 }

Libraries/LibIDL/Types.h

@@ -318,6 +318,7 @@ public:
     HashMap<ByteString, HashTable<ByteString>> included_mixins;
 
     ByteString module_own_path;
+    Vector<NonnullOwnPtr<Interface>> partial_interfaces;
     Vector<Interface&> imported_modules;
 
     HashMap<ByteString, Vector<Function&>> overload_sets;
@@ -337,6 +338,8 @@ public:
     {
         return !name.is_empty() || any_of(enumerations, [](auto& entry) { return entry.value.is_original_definition; });
     }
+
+    void extend_with_partial_interface(Interface const&);
 };
 
 class UnionType : public Type {