[objective_c] Fix a bug where toNSInputStream would keep listening to events unless NSInputStream.close is called (#2392)

brianquinlan · web-flow · commit 692c2da40f77 · 2025-07-21T16:47:06.000-07:00
diff --git a/pkgs/ffigen/lib/src/code_generator/objc_built_in_types.dart b/pkgs/ffigen/lib/src/code_generator/objc_built_in_types.dart
@@ -6,6 +6,7 @@
 
 const objCBuiltInInterfaces = {
   'DOBJCDartInputStreamAdapter': 'DartInputStreamAdapter',
+  'DOBJCDartInputStreamAdapterWeakHolder': 'DartInputStreamAdapterWeakHolder',
   'DOBJCObservation': 'DOBJCObservation',
   'DOBJCDartProtocolBuilder': 'DartProtocolBuilder',
   'DOBJCDartProtocol': 'DartProtocol',
diff --git a/pkgs/objective_c/CHANGELOG.md b/pkgs/objective_c/CHANGELOG.md
@@ -3,6 +3,8 @@
 - Bump minimum Dart version to 3.8.0.
 - Support the KVO pattern by adding `Observer`, `Observation`, and
   `NSObject.addObserver`.
+- Remove a reference cycle between Dart and the `NSInputStream` returned by
+  `toNSInputStream`.
 
 ## 8.0.0
 
diff --git a/pkgs/objective_c/ffigen_objc.yaml b/pkgs/objective_c/ffigen_objc.yaml
@@ -27,6 +27,7 @@ objc-interfaces:
   # Keep in sync with ffigen's ObjCBuiltInFunctions.builtInInterfaces.
   include:
     - DOBJCDartInputStreamAdapter
+    - DOBJCDartInputStreamAdapterWeakHolder
     - DOBJCObservation
     - DOBJCDartProtocolBuilder
     - DOBJCDartProtocol
@@ -72,6 +73,7 @@ objc-interfaces:
     - Protocol
   rename:
     'DOBJCDartInputStreamAdapter': 'DartInputStreamAdapter'
+    'DOBJCDartInputStreamAdapterWeakHolder' : 'DartInputStreamAdapterWeakHolder'
     'DOBJCDartProtocolBuilder': 'DartProtocolBuilder'
     'DOBJCDartProtocol': 'DartProtocol'
 objc-protocols:
diff --git a/pkgs/objective_c/lib/src/ns_input_stream.dart b/pkgs/objective_c/lib/src/ns_input_stream.dart
@@ -2,10 +2,22 @@ import 'dart:async';
 import 'dart:ffi';
 import 'dart:isolate';
 
-import 'ns_data.dart';
-import 'ns_string.dart';
+import '../objective_c.dart';
+
 import 'objective_c_bindings_generated.dart';
 
+@Native<Pointer<Void> Function()>(
+  isLeaf: true,
+  symbol: 'objc_autoreleasePoolPush',
+)
+external Pointer<Void> _autoreleasePoolPush();
+
+@Native<Void Function(Pointer<Void>)>(
+  isLeaf: true,
+  symbol: 'objc_autoreleasePoolPop',
+)
+external void _autoreleasePoolPop(Pointer<Void> pool);
+
 extension NSInputStreamStreamExtension on Stream<List<int>> {
   /// Return a [NSInputStream] that, when read, will contain the contents of
   /// the [Stream].
@@ -15,23 +27,57 @@ extension NSInputStreamStreamExtension on Stream<List<int>> {
   /// > than the one that calls [toNSInputStream]. Otherwise,
   /// > [NSInputStream.read] will deadlock waiting for data to be added from the
   /// > [Stream].
+  ///
+  /// > [!IMPORTANT]
+  /// > [NSInputStream.read] must be called from a different thread or [Isolate]
+  /// > than the one that calls `toNSInputStream`. Otherwise,
+  /// > [NSInputStream.read] will deadlock waiting for data to be added from the
+  /// > [Stream].
+  ///
+  /// > [!IMPORTANT]
+  /// > `toNSInputStream` creates a reference cycle between Dart and
+  /// > Objective-C. Unless this cycle is broken, the [Isolate] calling
+  /// > `toNSInputStream` will never exit. The cycle can be broken by calling
+  /// > [NSInputStream.close] or releasing the `NSInputStream` using
+  /// > `NSInputStream.ref.release()`.
   NSInputStream toNSInputStream() {
     // Eagerly add data until `maxReadAheadSize` is buffered.
     const maxReadAheadSize = 4096;
 
     final port = ReceivePort();
-    final inputStream = DartInputStreamAdapter.inputStreamWithPort(
-      port.sendPort.nativePort,
-    );
+
+    final DartInputStreamAdapter inputStream;
+    final DartInputStreamAdapterWeakHolder weakInputStream;
+
+    // Only hold a weak reference to the returned `inputStream` so that there is
+    // no unbreakable reference cycle between Dart and Objective-C. When the
+    // `inputStream`'s `dealloc` method is called then it sends this code a
+    // message saying that it was closed.
+    final pool = _autoreleasePoolPush();
+    try {
+      inputStream = DartInputStreamAdapter.inputStreamWithPort(
+        port.sendPort.nativePort,
+      );
+      weakInputStream =
+          DartInputStreamAdapterWeakHolder.holderWithInputStreamAdapter(
+            inputStream,
+          );
+    } finally {
+      _autoreleasePoolPop(pool);
+    }
+
     late final StreamSubscription<dynamic> dataSubscription;
 
     dataSubscription = listen(
       (data) {
+        final inputStream = weakInputStream.adapter;
         if (inputStream.addData(data.toNSData()) > maxReadAheadSize) {
           dataSubscription.pause();
         }
+        inputStream.ref.release();
       },
       onError: (Object e) {
+        final inputStream = weakInputStream.adapter;
         final d = NSMutableDictionary();
         d[NSLocalizedDescriptionKey] = e.toString().toNSString();
         inputStream.setError(
@@ -41,10 +87,13 @@ extension NSInputStreamStreamExtension on Stream<List<int>> {
             userInfo: d,
           ),
         );
+        inputStream.ref.release();
         port.close();
       },
       onDone: () {
+        final inputStream = weakInputStream.adapter;
         inputStream.setDone();
+        inputStream.ref.release();
         port.close();
       },
       cancelOnError: true,
diff --git a/pkgs/objective_c/lib/src/objective_c_bindings_generated.dart b/pkgs/objective_c/lib/src/objective_c_bindings_generated.dart
@@ -1129,6 +1129,154 @@ class DartInputStreamAdapter extends NSInputStream implements NSStreamDelegate {
   }
 }
 
+/// Helper class that contains a weak reference to a `DOBJCDartInputStreamAdapter`.
+class DartInputStreamAdapterWeakHolder extends NSObject {
+  DartInputStreamAdapterWeakHolder._(
+    ffi.Pointer<objc.ObjCObject> pointer, {
+    bool retain = false,
+    bool release = false,
+  }) : super.castFromPointer(pointer, retain: retain, release: release);
+
+  /// Constructs a [DartInputStreamAdapterWeakHolder] that points to the same underlying object as [other].
+  DartInputStreamAdapterWeakHolder.castFrom(objc.ObjCObjectBase other)
+    : this._(other.ref.pointer, retain: true, release: true);
+
+  /// Constructs a [DartInputStreamAdapterWeakHolder] that wraps the given raw object pointer.
+  DartInputStreamAdapterWeakHolder.castFromPointer(
+    ffi.Pointer<objc.ObjCObject> other, {
+    bool retain = false,
+    bool release = false,
+  }) : this._(other, retain: retain, release: release);
+
+  /// Returns whether [obj] is an instance of [DartInputStreamAdapterWeakHolder].
+  static bool isInstance(objc.ObjCObjectBase obj) {
+    return _objc_msgSend_19nvye5(
+      obj.ref.pointer,
+      _sel_isKindOfClass_,
+      _class_DOBJCDartInputStreamAdapterWeakHolder,
+    );
+  }
+
+  /// alloc
+  static DartInputStreamAdapterWeakHolder alloc() {
+    final _ret = _objc_msgSend_151sglz(
+      _class_DOBJCDartInputStreamAdapterWeakHolder,
+      _sel_alloc,
+    );
+    return DartInputStreamAdapterWeakHolder.castFromPointer(
+      _ret,
+      retain: false,
+      release: true,
+    );
+  }
+
+  /// allocWithZone:
+  static DartInputStreamAdapterWeakHolder allocWithZone(
+    ffi.Pointer<NSZone> zone,
+  ) {
+    final _ret = _objc_msgSend_1cwp428(
+      _class_DOBJCDartInputStreamAdapterWeakHolder,
+      _sel_allocWithZone_,
+      zone,
+    );
+    return DartInputStreamAdapterWeakHolder.castFromPointer(
+      _ret,
+      retain: false,
+      release: true,
+    );
+  }
+
+  /// holderWithInputStreamAdapter:
+  static DartInputStreamAdapterWeakHolder holderWithInputStreamAdapter(
+    DartInputStreamAdapter adapter,
+  ) {
+    final _ret = _objc_msgSend_1sotr3r(
+      _class_DOBJCDartInputStreamAdapterWeakHolder,
+      _sel_holderWithInputStreamAdapter_,
+      adapter.ref.pointer,
+    );
+    return DartInputStreamAdapterWeakHolder.castFromPointer(
+      _ret,
+      retain: true,
+      release: true,
+    );
+  }
+
+  /// new
+  static DartInputStreamAdapterWeakHolder new$() {
+    final _ret = _objc_msgSend_151sglz(
+      _class_DOBJCDartInputStreamAdapterWeakHolder,
+      _sel_new,
+    );
+    return DartInputStreamAdapterWeakHolder.castFromPointer(
+      _ret,
+      retain: false,
+      release: true,
+    );
+  }
+
+  /// adapter
+  DartInputStreamAdapter get adapter {
+    final _ret = _objc_msgSend_151sglz(this.ref.pointer, _sel_adapter);
+    return DartInputStreamAdapter.castFromPointer(
+      _ret,
+      retain: true,
+      release: true,
+    );
+  }
+
+  /// autorelease
+  DartInputStreamAdapterWeakHolder autorelease() {
+    final _ret = _objc_msgSend_151sglz(this.ref.pointer, _sel_autorelease);
+    return DartInputStreamAdapterWeakHolder.castFromPointer(
+      _ret,
+      retain: true,
+      release: true,
+    );
+  }
+
+  /// init
+  DartInputStreamAdapterWeakHolder init() {
+    objc.checkOsVersionInternal(
+      'DOBJCDartInputStreamAdapterWeakHolder.init',
+      iOS: (false, (2, 0, 0)),
+      macOS: (false, (10, 0, 0)),
+    );
+    final _ret = _objc_msgSend_151sglz(
+      this.ref.retainAndReturnPointer(),
+      _sel_init,
+    );
+    return DartInputStreamAdapterWeakHolder.castFromPointer(
+      _ret,
+      retain: false,
+      release: true,
+    );
+  }
+
+  /// retain
+  DartInputStreamAdapterWeakHolder retain() {
+    final _ret = _objc_msgSend_151sglz(this.ref.pointer, _sel_retain);
+    return DartInputStreamAdapterWeakHolder.castFromPointer(
+      _ret,
+      retain: true,
+      release: true,
+    );
+  }
+
+  /// self
+  DartInputStreamAdapterWeakHolder self$1() {
+    final _ret = _objc_msgSend_151sglz(this.ref.pointer, _sel_self);
+    return DartInputStreamAdapterWeakHolder.castFromPointer(
+      _ret,
+      retain: true,
+      release: true,
+    );
+  }
+
+  /// Returns a new instance of DartInputStreamAdapterWeakHolder constructed with the default `new` method.
+  factory DartInputStreamAdapterWeakHolder() => new$();
+}
+
 /// Base class of all classes DOBJCDartProtocolBuilder creates.
 class DartProtocol extends NSObject {
   DartProtocol._(
@@ -34547,6 +34695,9 @@ class Protocol extends objc.ObjCObjectBase {
 late final _class_DOBJCDartInputStreamAdapter = objc.getClass(
   "DOBJCDartInputStreamAdapter",
 );
+late final _class_DOBJCDartInputStreamAdapterWeakHolder = objc.getClass(
+  "DOBJCDartInputStreamAdapterWeakHolder",
+);
 late final _class_DOBJCDartProtocol = objc.getClass("DOBJCDartProtocol");
 late final _class_DOBJCDartProtocolBuilder = objc.getClass(
   "DOBJCDartProtocolBuilder",
@@ -38828,6 +38979,7 @@ late final _sel_absoluteURLWithDataRepresentation_relativeToURL_ = objc
 late final _sel_acceptInputForMode_beforeDate_ = objc.registerName(
   "acceptInputForMode:beforeDate:",
 );
+late final _sel_adapter = objc.registerName("adapter");
 late final _sel_addChild_withPendingUnitCount_ = objc.registerName(
   "addChild:withPendingUnitCount:",
 );
@@ -39255,6 +39407,9 @@ late final _sel_hasSpaceAvailable = objc.registerName("hasSpaceAvailable");
 late final _sel_hasSuffix_ = objc.registerName("hasSuffix:");
 late final _sel_hash = objc.registerName("hash");
 late final _sel_helpAnchor = objc.registerName("helpAnchor");
+late final _sel_holderWithInputStreamAdapter_ = objc.registerName(
+  "holderWithInputStreamAdapter:",
+);
 late final _sel_host = objc.registerName("host");
 late final _sel_illegalCharacterSet = objc.registerName("illegalCharacterSet");
 late final _sel_implementMethod_withBlock_withTrampoline_withSignature_ = objc
diff --git a/pkgs/objective_c/src/input_stream_adapter.h b/pkgs/objective_c/src/input_stream_adapter.h
@@ -20,3 +20,11 @@
 - (void)setDone;
 - (void)setError:(NSError *)error;
 @end
+
+/// Helper class that contains a weak reference to a `DOBJCDartInputStreamAdapter`.
+@interface DOBJCDartInputStreamAdapterWeakHolder : NSObject
+
++ (instancetype)holderWithInputStreamAdapter:(DOBJCDartInputStreamAdapter *)adapter;
+@property(nonatomic, readonly, weak) DOBJCDartInputStreamAdapter* adapter;
+
+@end
diff --git a/pkgs/objective_c/src/input_stream_adapter.m b/pkgs/objective_c/src/input_stream_adapter.m
@@ -33,6 +33,12 @@ + (instancetype)inputStreamWithPort:(Dart_Port)sendPort {
   return stream;
 }
 
+- (void)dealloc {
+  if (_status != NSStreamStatusClosed) {
+    Dart_PostInteger_DL(_sendPort, -1);
+  }
+}
+
 - (NSUInteger)addData:(NSData *)data {
   [_dataCondition lock];
   [_data appendData:data];
@@ -167,3 +173,16 @@ - (void)stream:(NSStream *)theStream handleEvent:(NSStreamEvent)streamEvent {
 }
 
 @end
+
+@implementation DOBJCDartInputStreamAdapterWeakHolder
++ (instancetype)holderWithInputStreamAdapter:(DOBJCDartInputStreamAdapter *)adapter {
+  DOBJCDartInputStreamAdapterWeakHolder * holder = [[DOBJCDartInputStreamAdapterWeakHolder alloc] init]; 
+  if (holder != nil) {
+    holder->adapter = adapter;
+  }
+  return holder;
+}
+
+@synthesize adapter;
+
+@end
diff --git a/pkgs/objective_c/test/ns_input_stream_test.dart b/pkgs/objective_c/test/ns_input_stream_test.dart
diff --git a/pkgs/objective_c/tool/generate_code.dart b/pkgs/objective_c/tool/generate_code.dart
