[swift2objc] Support Protocols

pkgs/swift2objc/lib/src/ast/declarations/compounds/protocol_declaration.dart

@@ -4,13 +4,14 @@
 
 import '../../_core/interfaces/compound_declaration.dart';
 import '../../_core/interfaces/nestable_declaration.dart';
+import '../../_core/interfaces/objc_annotatable.dart';
 import '../../_core/shared/referred_type.dart';
 import 'members/initializer_declaration.dart';
 import 'members/method_declaration.dart';
 import 'members/property_declaration.dart';
 
 /// Describes the declaration of a Swift protocol.
-class ProtocolDeclaration implements CompoundDeclaration {
+class ProtocolDeclaration implements CompoundDeclaration, ObjCAnnotatable {
   @override
   String id;
 
@@ -23,9 +24,20 @@ class ProtocolDeclaration implements CompoundDeclaration {
   @override
   covariant List<MethodDeclaration> methods;
 
+  /// Only present if indicated with `@objc`
+  @override
+  List<PropertyDeclaration> optionalProperties;
+
+  /// Only present if indicated with `@objc`
+  @override
+  List<MethodDeclaration> optionalMethods;
+
   @override
   List<DeclaredType<ProtocolDeclaration>> conformedProtocols;
 
+  @override
+  bool hasObjCAnnotation;
+
   @override
   List<GenericType> typeParams;
 
@@ -46,7 +58,10 @@ class ProtocolDeclaration implements CompoundDeclaration {
     required this.initializers,
     required this.conformedProtocols,
     required this.typeParams,
+    this.hasObjCAnnotation = false,
     this.nestingParent,
     this.nestedDeclarations = const [],
+    this.optionalMethods = const [],
+    this.optionalProperties = const [],
   });
 }

pkgs/swift2objc/lib/src/parser/_core/parsed_symbolgraph.dart

@@ -35,6 +35,10 @@ class ParsedRelation {
 }
 
 enum ParsedRelationKind {
+  requirementOf,
+  defaultImplementationOf,
+  optionalRequirementOf,
+  conformsTo,
   memberOf;
 
   static final _supportedRelationKindsMap = {

pkgs/swift2objc/lib/src/parser/parsers/declaration_parsers/parse_compound_declaration.dart

@@ -3,11 +3,13 @@
 // BSD-style license that can be found in the LICENSE file.
 
 import '../../../ast/_core/interfaces/compound_declaration.dart';
+import '../../../ast/_core/interfaces/declaration.dart';
 import '../../../ast/_core/interfaces/nestable_declaration.dart';
 import '../../../ast/declarations/compounds/class_declaration.dart';
 import '../../../ast/declarations/compounds/members/initializer_declaration.dart';
 import '../../../ast/declarations/compounds/members/method_declaration.dart';
 import '../../../ast/declarations/compounds/members/property_declaration.dart';
+import '../../../ast/declarations/compounds/protocol_declaration.dart';
 import '../../../ast/declarations/compounds/struct_declaration.dart';
 import '../../_core/parsed_symbolgraph.dart';
 import '../../_core/utils.dart';
@@ -107,3 +109,128 @@ StructDeclaration parseStructDeclaration(
     symbolgraph,
   );
 }
+
+// This won't work as there's more for a protocol declaration
+// Placing this here as placeholder declaration
+// TODO: Implement extensions before adding support for default implementations
+  // 5. protocol func with reimpl in extension -> requirementOf 
+  //  and defaultImplementationOf, swift.method
+  // 6. protocol var with reimpl in extension -> requirementOf 
+  //  and defaultImplementationOf, swift.property,
+// TODO: Replace generics to associatedType and implement
+ProtocolDeclaration parseProtocolDeclaration(
+  ParsedSymbol protocolSymbol,
+  ParsedSymbolgraph symbolgraph
+) {
+  final compoundId = parseSymbolId(protocolSymbol.json);
+  final compoundRelations = symbolgraph.relations[compoundId] ?? [];
+
+  // construct protocol
+  final protocol = ProtocolDeclaration(
+    id: compoundId, name: parseSymbolName(protocolSymbol.json), 
+    properties: [], 
+    methods: [], 
+    initializers: [], 
+    conformedProtocols: [], 
+    typeParams: []
+  );
+
+  // get optional member declarations if any
+  final optionalMemberDeclarations = compoundRelations.where((relation) {
+    final isOptionalRequirementRelation = 
+      relation.kind == ParsedRelationKind.optionalRequirementOf;
+    final isMemberOfProtocol = relation.targetId == compoundId;
+    return isMemberOfProtocol && isOptionalRequirementRelation;
+  }).map((relation) {
+    final memberSymbol = symbolgraph.symbols[relation.sourceId];
+    if (memberSymbol == null) {
+      return null;
+    }
+    return tryParseDeclaration(memberSymbol, symbolgraph);
+  })
+  .nonNulls
+  .dedupeBy((decl) => decl.id)
+  .toList()
+  ;
+
+  // get normal member declarations
+  final memberDeclarations = compoundRelations.where((relation) {
+    final isOptionalRequirementRelation = 
+      relation.kind == ParsedRelationKind.requirementOf 
+      && relation.kind != ParsedRelationKind.optionalRequirementOf;
+    final isMemberOfProtocol = relation.targetId == compoundId;
+    return isMemberOfProtocol && isOptionalRequirementRelation;
+  }).map((relation) {
+    final memberSymbol = symbolgraph.symbols[relation.sourceId];
+    if (memberSymbol == null) {
+      return null;
+    }
+    return tryParseDeclaration(memberSymbol, symbolgraph);
+  })
+  .nonNulls
+  .dedupeBy((decl) => decl.id)
+  .toList()
+  ;
+
+  // get conformed protocols
+  final conformedProtocolDeclarations = compoundRelations.where((relation) {
+    final isOptionalRequirementRelation = 
+      relation.kind == ParsedRelationKind.conformsTo;
+    final isMemberOfProtocol = relation.targetId == compoundId;
+    return isMemberOfProtocol && isOptionalRequirementRelation;
+  }).map((relation) {
+    final memberSymbol = symbolgraph.symbols[relation.sourceId];
+    if (memberSymbol == null) {
+      return null;
+    }
+    var conformedDecl = tryParseDeclaration(memberSymbol, symbolgraph) as ProtocolDeclaration;
+    return conformedDecl.asDeclaredType;
+  })
+  .nonNulls
+  .dedupeBy((decl) => decl.id)
+  .toList()
+  ;
+
+  // If the protocol has optional members, it must be annotated with `@objc`
+  if (optionalMemberDeclarations.isNotEmpty) {
+    protocol.hasObjCAnnotation = true;
+  }
+
+  protocol.methods.addAll(
+    memberDeclarations
+        .whereType<MethodDeclaration>()
+        .dedupeBy((m) => m.fullName),
+  );
+
+  protocol.properties.addAll(
+    memberDeclarations.whereType<PropertyDeclaration>(),
+  );
+
+  protocol.optionalMethods.addAll(
+    optionalMemberDeclarations
+        .whereType<MethodDeclaration>()
+        .dedupeBy((m) => m.fullName),
+  );
+
+  protocol.optionalProperties.addAll(
+    optionalMemberDeclarations.whereType<PropertyDeclaration>(),
+  );
+
+  protocol.conformedProtocols.addAll(
+    conformedProtocolDeclarations
+  );
+
+  protocol.initializers.addAll(
+    memberDeclarations
+        .whereType<InitializerDeclaration>()
+        .dedupeBy((m) => m.fullName),
+  );
+
+  protocol.nestedDeclarations.addAll(
+    memberDeclarations.whereType<NestableDeclaration>(),
+  );
+
+  protocol.nestedDeclarations.fillNestingParents(protocol);
+
+  return protocol;
+}

pkgs/swift2objc/lib/src/parser/parsers/parse_declarations.dart

@@ -56,6 +56,7 @@ Declaration parseDeclaration(
     'swift.init' => parseInitializerDeclaration(symbolJson, symbolgraph),
     'swift.func' => parseGlobalFunctionDeclaration(symbolJson, symbolgraph),
     'swift.var' => parseGlobalVariableDeclaration(symbolJson, symbolgraph),
+    'swift.protocol' => parseProtocolDeclaration(parsedSymbol, symbolgraph),
     _ => throw Exception(
         'Symbol of type $symbolType is not implemented yet.',
       ),