[swift2objc] Support throws annotation (#1766)

Author: liamappelbe

pkgs/swift2objc/lib/src/ast/_core/interfaces/can_throw.dart

@@ -0,0 +1,9 @@
+// Copyright (c) 2024, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+/// An interface to describe a Swift entity's ability to be annotated
+/// with `throws`.
+abstract interface class CanThrow {
+  abstract final bool throws;
+}

pkgs/swift2objc/lib/src/ast/_core/interfaces/function_declaration.dart

@@ -3,13 +3,19 @@
 // BSD-style license that can be found in the LICENSE file.
 
 import '../shared/referred_type.dart';
+import 'can_throw.dart';
 import 'declaration.dart';
 import 'executable.dart';
 import 'parameterizable.dart';
 import 'type_parameterizable.dart';
 
 /// Describes a function-like entity.
 abstract interface class FunctionDeclaration
-    implements Declaration, Parameterizable, Executable, TypeParameterizable {
+    implements
+        Declaration,
+        Parameterizable,
+        Executable,
+        TypeParameterizable,
+        CanThrow {
   abstract final ReferredType returnType;
 }

pkgs/swift2objc/lib/src/ast/_core/interfaces/overridable.dart

@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 /// An interface to describe a Swift entity's ability to be annotated
-/// with `@objc`.
+/// with `override`.
 abstract interface class Overridable {
   abstract final bool isOverriding;
 }

pkgs/swift2objc/lib/src/ast/_core/interfaces/variable_declaration.dart

@@ -3,10 +3,15 @@
 // BSD-style license that can be found in the LICENSE file.
 
 import '../shared/referred_type.dart';
+import 'can_throw.dart';
 import 'declaration.dart';
 
 /// Describes a variable-like entity.
-abstract interface class VariableDeclaration implements Declaration {
+///
+/// This declaration [CanThrow] because Swift variables can have explicit
+/// getters, which can be marked with `throws`. Such variables may not have a
+/// setter.
+abstract interface class VariableDeclaration implements Declaration, CanThrow {
   abstract final bool isConstant;
   abstract final ReferredType type;
 }

pkgs/swift2objc/lib/src/ast/declarations/compounds/members/initializer_declaration.dart

@@ -2,6 +2,7 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
+import '../../../_core/interfaces/can_throw.dart';
 import '../../../_core/interfaces/declaration.dart';
 import '../../../_core/interfaces/executable.dart';
 import '../../../_core/interfaces/objc_annotatable.dart';
@@ -16,7 +17,8 @@ class InitializerDeclaration
         Executable,
         Parameterizable,
         ObjCAnnotatable,
-        Overridable {
+        Overridable,
+        CanThrow {
   @override
   String id;
 
@@ -29,6 +31,9 @@ class InitializerDeclaration
   @override
   bool isOverriding;
 
+  @override
+  bool throws;
+
   bool isFailable;
 
   @override
@@ -48,6 +53,7 @@ class InitializerDeclaration
     this.statements = const [],
     required this.hasObjCAnnotation,
     required this.isOverriding,
+    required this.throws,
     required this.isFailable,
   });
 }

pkgs/swift2objc/lib/src/ast/declarations/compounds/members/method_declaration.dart

@@ -30,6 +30,9 @@ class MethodDeclaration
   @override
   bool isOverriding;
 
+  @override
+  bool throws;
+
   @override
   List<String> statements;
 
@@ -53,5 +56,6 @@ class MethodDeclaration
     this.statements = const [],
     this.isStatic = false,
     this.isOverriding = false,
+    this.throws = false,
   }) : assert(!isStatic || !isOverriding);
 }

pkgs/swift2objc/lib/src/ast/declarations/compounds/members/property_declaration.dart

@@ -25,6 +25,9 @@ class PropertyDeclaration implements VariableDeclaration, ObjCAnnotatable {
   @override
   bool isConstant;
 
+  @override
+  bool throws;
+
   bool hasSetter;
 
   PropertyStatements? getter;
@@ -42,7 +45,9 @@ class PropertyDeclaration implements VariableDeclaration, ObjCAnnotatable {
     this.getter,
     this.setter,
     this.isStatic = false,
-  }) : assert(!isConstant || !hasSetter);
+    this.throws = false,
+  })  : assert(!(isConstant && hasSetter)),
+        assert(!(hasSetter && throws));
 }
 
 class PropertyStatements implements Executable {

pkgs/swift2objc/lib/src/ast/declarations/globals/globals.dart

@@ -33,6 +33,9 @@ class GlobalFunctionDeclaration implements FunctionDeclaration {
   @override
   List<GenericType> typeParams;
 
+  @override
+  bool throws;
+
   @override
   ReferredType returnType;
 
@@ -46,6 +49,7 @@ class GlobalFunctionDeclaration implements FunctionDeclaration {
     required this.returnType,
     this.typeParams = const [],
     this.statements = const [],
+    this.throws = false,
   });
 }
 
@@ -63,10 +67,14 @@ class GlobalVariableDeclaration implements VariableDeclaration {
   @override
   bool isConstant;
 
+  @override
+  bool throws;
+
   GlobalVariableDeclaration({
     required this.id,
     required this.name,
     required this.type,
     required this.isConstant,
-  });
+    required this.throws,
+  }) : assert(!(throws && !isConstant));
 }

pkgs/swift2objc/lib/src/generator/generators/class_generator.dart

@@ -87,6 +87,10 @@ List<String> _generateInitializer(InitializerDeclaration initializer) {
 
   header.write('(${generateParameters(initializer.params)})');
 
+  if (initializer.throws) {
+    header.write(' throws');
+  }
+
   return [
     '$header {',
     ...initializer.statements.indent(),
@@ -116,6 +120,10 @@ List<String> _generateClassMethod(MethodDeclaration method) {
     'public func ${method.name}(${generateParameters(method.params)})',
   );
 
+  if (method.throws) {
+    header.write(' throws');
+  }
+
   if (!method.returnType.sameAs(voidType)) {
     header.write(' -> ${method.returnType.swiftType}');
   }

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

@@ -2,7 +2,6 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-import 'dart:collection';
 import 'dart:convert';
 
 /// This is a helper class that helps with parsing Json values. It supports
@@ -18,13 +17,13 @@ import 'dart:convert';
 /// The class is also an `Iterable` so if the json is an array, you can directly
 /// iterate over it with a `for` loop. If the json isn't an array, attempting to
 /// iterate over it will throw an error.
-class Json extends IterableBase<Json> {
-  final List<String> _pathSegments;
+class Json extends Iterable<Json> {
+  final List<String> pathSegments;
   final dynamic _json;
 
-  String get path => _pathSegments.join('/');
+  String get path => pathSegments.join('/');
 
-  Json(this._json, [this._pathSegments = const []]);
+  Json(this._json, [this.pathSegments = const []]);
 
   /// The subscript syntax is intended to access a value at a field of a map or
   /// at an index if an array, and thus, the `index` parameter here can either
@@ -37,7 +36,7 @@ class Json extends IterableBase<Json> {
           'Expected a map at "$path", found a ${_json.runtimeType}',
         );
       }
-      return Json(_json[index], [..._pathSegments, index]);
+      return Json(_json[index], [...pathSegments, index]);
     }
 
     if (index is int) {
@@ -57,7 +56,7 @@ class Json extends IterableBase<Json> {
           'Invalid negative index at "$path" (supplied index: $index)',
         );
       }
-      return Json(_json[index], [..._pathSegments, '$index']);
+      return Json(_json[index], [...pathSegments, '$index']);
     }
 
     throw Exception(
@@ -115,7 +114,7 @@ class _JsonIterator implements Iterator<Json> {
   _JsonIterator(this._json) : _list = _json.get();
 
   @override
-  Json get current => Json(_list[_index], [..._json._pathSegments, '$_index']);
+  Json get current => Json(_list[_index], [..._json.pathSegments, '$_index']);
 
   @override
   bool moveNext() {

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

@@ -2,6 +2,8 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
+import 'package:meta/meta.dart';
+
 import 'json.dart';
 import 'utils.dart';
 
@@ -15,7 +17,7 @@ import 'utils.dart';
 /// can pass it to parseType, because certain tokens get concatenated by the
 /// swift compiler. This class performs that preprocessing, as well as providing
 /// convenience methods for parsing, like slicing.
-class TokenList {
+class TokenList extends Iterable<Json> {
   final List<Json> _list;
   final int _start;
   final int _end;
@@ -24,30 +26,55 @@ class TokenList {
       : assert(0 <= _start && _start <= _end && _end <= _list.length);
 
   factory TokenList(Json fragments) {
-    const splits = {
-      '?(': ['?', '('],
-      '?)': ['?', ')'],
-      '?, ': ['?', ', '],
-      ') -> ': [')', '->'],
-      '?) -> ': ['?', ')', '->'],
-    };
-
-    final list = <Json>[];
-    for (final token in fragments) {
-      final split = splits[getSpellingForKind(token, 'text')];
-      if (split != null) {
-        for (final sub in split) {
-          list.add(Json({'kind': 'text', 'spelling': sub}));
+    final list = [for (final token in fragments) ...splitToken(token)];
+    return TokenList._(list, 0, list.length);
+  }
+
+  @visibleForTesting
+  static Iterable<Json> splitToken(Json token) sync* {
+    const splittables = ['(', ')', '?', ',', '->'];
+    Json textToken(String text) =>
+        Json({'kind': 'text', 'spelling': text}, token.pathSegments);
+
+    final text = getSpellingForKind(token, 'text')?.trim();
+    if (text == null) {
+      // Not a text token. Pass it though unchanged.
+      yield token;
+      return;
+    }
+
+    if (text.isEmpty) {
+      // Input text token was nothing but whitespace. The loop below would yield
+      // nothing, but we still need it as a separator.
+      yield textToken(text);
+      return;
+    }
+
+    var suffix = text;
+    while (true) {
+      var any = false;
+      for (final prefix in splittables) {
+        if (suffix.startsWith(prefix)) {
+          yield textToken(prefix);
+          suffix = suffix.substring(prefix.length).trim();
+          any = true;
+          break;
         }
-      } else {
-        list.add(token);
+      }
+      if (!any) {
+        // Remaining text isn't splittable.
+        if (suffix.isNotEmpty) yield textToken(suffix);
+        break;
       }
     }
-    return TokenList._(list, 0, list.length);
   }
 
+  @override
   int get length => _end - _start;
-  bool get isEmpty => length == 0;
+
+  @override
+  Iterator<Json> get iterator => _TokenListIterator(this);
+
   Json operator [](int index) => _list[index + _start];
 
   int indexWhere(bool Function(Json element) test) {
@@ -63,3 +90,19 @@ class TokenList {
   @override
   String toString() => _list.getRange(_start, _end).toString();
 }
+
+class _TokenListIterator implements Iterator<Json> {
+  final TokenList _list;
+  var _index = -1;
+
+  _TokenListIterator(this._list);
+
+  @override
+  Json get current => _list[_index];
+
+  @override
+  bool moveNext() {
+    _index++;
+    return _index < _list.length;
+  }
+}

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

@@ -107,7 +107,7 @@ ReferredType parseTypeAfterSeparator(
 ) {
   // fragments = [..., ': ', type tokens...]
   final separatorIndex =
-      fragments.indexWhere((token) => matchFragment(token, 'text', ': '));
+      fragments.indexWhere((token) => matchFragment(token, 'text', ':'));
   final (type, suffix) =
       parseType(symbolgraph, fragments.slice(separatorIndex + 1));
   assert(suffix.isEmpty, '$suffix');