Fix corner case errors in platform channels (#3631)

shell/platform/android/io/flutter/plugin/common/BasicMessageChannel.java

@@ -154,12 +154,7 @@ public final class BasicMessageChannel<T> {
                 handler.onMessage(codec.decodeMessage(message), new Reply<T>() {
                     @Override
                     public void reply(T reply) {
-                        try {
-                            callback.reply(codec.encodeMessage(reply));
-                        } catch (RuntimeException e) {
-                            Log.e(TAG + name, "Failed to encode reply", e);
-                            callback.reply(null);
-                        }
+                        callback.reply(codec.encodeMessage(reply));
                     }
                 });
             } catch (RuntimeException e) {

shell/platform/android/io/flutter/plugin/common/BinaryMessenger.java

@@ -17,8 +17,8 @@ public interface BinaryMessenger {
      * Sends a binary message to the Flutter application.
      *
      * @param channel the name {@link String} of the logical channel used for the message.
-     * @param message the message payload, a {@link ByteBuffer} with the message bytes between position
-     * zero and current position, or null.
+     * @param message the message payload, a direct-allocated {@link ByteBuffer} with the message bytes
+     * between position zero and current position, or null.
      */
     void send(String channel, ByteBuffer message);
 
@@ -28,8 +28,8 @@ public interface BinaryMessenger {
      * <p>Any uncaught exception thrown by the reply callback will be caught and logged.</p>
      *
      * @param channel the name {@link String} of the logical channel used for the message.
-     * @param message the message payload, a {@link ByteBuffer} with the message bytes between position
-     * zero and current position, or null.
+     * @param message the message payload, a direct-allocated {@link ByteBuffer} with the message bytes
+     * between position zero and current position, or null.
      * @param callback a {@link BinaryReply} callback invoked when the Flutter application responds to the
      * message, possibly null.
      */
@@ -79,8 +79,8 @@ public interface BinaryMessenger {
         /**
          * Handles the specified reply.
          *
-         * @param reply the reply payload, a {@link ByteBuffer} or null. Senders of outgoing
-         * replies must place the reply bytes between position zero and current position.
+         * @param reply the reply payload, a direct-allocated {@link ByteBuffer} or null. Senders of
+         * outgoing replies must place the reply bytes between position zero and current position.
          * Reply receivers can read from the buffer directly.
          */
         void reply(ByteBuffer reply);

shell/platform/android/io/flutter/plugin/common/EventChannel.java

@@ -91,13 +91,8 @@ public final class EventChannel {
         /**
          * Handles a request to set up an event stream.
          *
-         * <p>Any uncaught exception thrown by this method, or the preceding arguments
-         * decoding, will be caught by the channel implementation and logged. An error result
-         * message will be sent back to Flutter.</p>
-         *
-         * <p>Any uncaught exception thrown during encoding an event or error submitted to the
-         * {@link EventSink} is treated similarly: the exception is logged, and an error event
-         * is sent to Flutter.</p>
+         * <p>Any uncaught exception thrown by this method will be caught by the channel
+         * implementation and logged. An error result message will be sent back to Flutter.</p>
          *
          * @param arguments stream configuration arguments, possibly null.
          * @param events an {@link EventSink} for emitting events to the Flutter receiver.
@@ -107,9 +102,8 @@ public final class EventChannel {
         /**
          * Handles a request to tear down an event stream.
          *
-         * <p>Any uncaught exception thrown by this method, or the preceding arguments
-         * decoding, will be caught by the channel implementation and logged. An error result
-         * result message will be sent back to Flutter.</p>
+         * <p>Any uncaught exception thrown by this method will be caught by the channel
+         * implementation and logged. An error result message will be sent back to Flutter.</p>
          *
          * @param arguments stream configuration arguments, possibly null.
          */
@@ -156,18 +150,13 @@ public final class EventChannel {
 
         @Override
         public void onMessage(ByteBuffer message, final BinaryReply reply) {
-            try {
-                final MethodCall call = codec.decodeMethodCall(message);
-                if (call.method.equals("listen")) {
-                    onListen(call.arguments, reply);
-                } else if (call.method.equals("cancel")) {
-                    onCancel(call.arguments, reply);
-                } else {
-                    reply.reply(null);
-                }
-            } catch (RuntimeException e) {
-                Log.e(TAG + name, "Failed to decode event stream lifecycle call", e);
-                reply.reply(codec.encodeErrorEnvelope("decode", e.getMessage(), null));
+            final MethodCall call = codec.decodeMethodCall(message);
+            if (call.method.equals("listen")) {
+                onListen(call.arguments, reply);
+            } else if (call.method.equals("cancel")) {
+                onCancel(call.arguments, reply);
+            } else {
+                reply.reply(null);
             }
         }
 
@@ -180,7 +169,7 @@ public final class EventChannel {
                 } catch (RuntimeException e) {
                     activeSink.set(null);
                     Log.e(TAG + name, "Failed to open event stream", e);
-                    callback.reply(codec.encodeErrorEnvelope("uncaught", e.getMessage(), null));
+                    callback.reply(codec.encodeErrorEnvelope("error", e.getMessage(), null));
                 }
             } else {
                 callback.reply(codec.encodeErrorEnvelope("error", "Stream already active", null));
@@ -195,7 +184,7 @@ public final class EventChannel {
                     callback.reply(codec.encodeSuccessEnvelope(null));
                 } catch (RuntimeException e) {
                     Log.e(TAG + name, "Failed to close event stream", e);
-                    callback.reply(codec.encodeErrorEnvelope("uncaught", e.getMessage(), null));
+                    callback.reply(codec.encodeErrorEnvelope("error", e.getMessage(), null));
                 }
             } else {
                 callback.reply(codec.encodeErrorEnvelope("error", "No active stream to cancel", null));
@@ -210,12 +199,7 @@ public final class EventChannel {
                  if (hasEnded.get() || activeSink.get() != this) {
                      return;
                  }
-                 try {
-                     EventChannel.this.messenger.send(name, codec.encodeSuccessEnvelope(event));
-                 } catch (RuntimeException e) {
-                     Log.e(TAG + name, "Failed to encode event", e);
-                     EventChannel.this.messenger.send(name, codec.encodeErrorEnvelope("encode", e.getMessage(), null));
-                 }
+                 EventChannel.this.messenger.send(name, codec.encodeSuccessEnvelope(event));
              }
 
              @Override
@@ -223,14 +207,9 @@ public final class EventChannel {
                  if (hasEnded.get() || activeSink.get() != this) {
                      return;
                  }
-                 try {
-                   EventChannel.this.messenger.send(
-                       name,
-                       codec.encodeErrorEnvelope(errorCode, errorMessage, errorDetails));
-                 } catch (RuntimeException e) {
-                     Log.e(TAG + name, "Failed to encode error", e);
-                     EventChannel.this.messenger.send(name, codec.encodeErrorEnvelope("encode", e.getMessage(), null));
-                 }
+                 EventChannel.this.messenger.send(
+                     name,
+                     codec.encodeErrorEnvelope(errorCode, errorMessage, errorDetails));
              }
 
              @Override

shell/platform/android/io/flutter/plugin/common/JSONMessageCodec.java

@@ -26,7 +26,12 @@ public final class JSONMessageCodec implements MessageCodec<Object> {
         if (message == null) {
             return null;
         }
-        return StringCodec.INSTANCE.encodeMessage(JSONUtil.wrap(message).toString());
+        final Object wrapped = JSONUtil.wrap(message);
+        if (wrapped instanceof String) {
+          return StringCodec.INSTANCE.encodeMessage(JSONObject.quote((String) wrapped));
+        } else {
+          return StringCodec.INSTANCE.encodeMessage(wrapped.toString());
+        }
     }
 
     @Override

shell/platform/android/io/flutter/plugin/common/JSONMethodCodec.java

@@ -36,7 +36,7 @@ public final class JSONMethodCodec implements MethodCodec {
             if (json instanceof JSONObject) {
                 final JSONObject map = (JSONObject) json;
                 final Object method = map.get("method");
-                final Object arguments = map.get("args");
+                final Object arguments = unwrapNull(map.opt("args"));
                 if (method instanceof String) {
                     return new MethodCall((String) method, arguments);
                 }
@@ -58,7 +58,7 @@ public final class JSONMethodCodec implements MethodCodec {
         Object errorDetails) {
         return JSONMessageCodec.INSTANCE.encodeMessage(new JSONArray()
             .put(errorCode)
-            .put(errorMessage)
+            .put(JSONUtil.wrap(errorMessage))
             .put(JSONUtil.wrap(errorDetails)));
     }
 
@@ -69,20 +69,24 @@ public final class JSONMethodCodec implements MethodCodec {
             if (json instanceof JSONArray) {
                 final JSONArray array = (JSONArray) json;
                 if (array.length() == 1) {
-                    return array.get(0);
+                    return unwrapNull(array.opt(0));
                 }
                 if (array.length() == 3) {
                     final Object code = array.get(0);
-                    final Object message = array.get(1);
-                    final Object details = array.get(2);
+                    final Object message = unwrapNull(array.opt(1));
+                    final Object details = unwrapNull(array.opt(2));
                     if (code instanceof String && (message == null || message instanceof String)) {
                         throw new FlutterException((String) code, (String) message, details);
                     }
                 }
             }
-            throw new IllegalArgumentException("Invalid method call: " + json);
+            throw new IllegalArgumentException("Invalid envelope: " + json);
         } catch (JSONException e) {
             throw new IllegalArgumentException("Invalid JSON", e);
         }
     }
+
+    Object unwrapNull(Object value) {
+      return (value == JSONObject.NULL) ? null : value;
+    }
 }

shell/platform/android/io/flutter/plugin/common/MethodChannel.java

@@ -114,11 +114,8 @@ public final class MethodChannel {
          * handlers. The result may be submitted asynchronously. Calls to unknown or unimplemented methods
          * should be handled using {@link Result#notImplemented()}.</p>
          *
-         * <p>Any uncaught exception thrown by this method, or the preceding method call decoding, will be
-         * caught by the channel implementation and logged, and an error result will be sent back to Flutter.</p>
-         *
-         * <p>Any uncaught exception thrown during encoding a result submitted to the {@link Result}
-         * is treated similarly: the exception is logged, and an error result is sent to Flutter.</p>
+         * <p>Any uncaught exception thrown by this method will be caught by the channel implementation and
+         * logged, and an error result will be sent back to Flutter.</p>
          *
          * @param call A {@link MethodCall}.
          * @param result A {@link Result} used for submitting the result of the call.
@@ -169,8 +166,7 @@ public final class MethodChannel {
                     callback.notImplemented();
                 } else {
                     try {
-                        final Object result = codec.decodeEnvelope(reply);
-                        callback.success(result);
+                        callback.success(codec.decodeEnvelope(reply));
                     } catch (FlutterException e) {
                         callback.error(e.code, e.getMessage(), e.details);
                     }
@@ -190,35 +186,17 @@ public final class MethodChannel {
 
         @Override
         public void onMessage(ByteBuffer message, final BinaryReply reply) {
-            MethodCall call;
-            try {
-                call = codec.decodeMethodCall(message);
-            } catch (RuntimeException e) {
-                Log.e(TAG + name, "Failed to decode method call", e);
-                reply.reply(codec.encodeErrorEnvelope("decode", e.getMessage(), null));
-                return;
-            }
+            final MethodCall call = codec.decodeMethodCall(message);
             try {
                 handler.onMethodCall(call, new Result() {
                     @Override
                     public void success(Object result) {
-                        try {
-                            reply.reply(codec.encodeSuccessEnvelope(result));
-                        } catch (RuntimeException e) {
-                            Log.e(TAG + name, "Failed to encode success result", e);
-                            reply.reply(codec.encodeErrorEnvelope("encode", e.getMessage(), null));
-                        }
+                        reply.reply(codec.encodeSuccessEnvelope(result));
                     }
 
                     @Override
                     public void error(String errorCode, String errorMessage, Object errorDetails) {
-                        try {
-                            reply.reply(codec.encodeErrorEnvelope(
-                                    errorCode, errorMessage, errorDetails));
-                        } catch (RuntimeException e) {
-                            Log.e(TAG + name, "Failed to encode error result", e);
-                            reply.reply(codec.encodeErrorEnvelope("encode", e.getMessage(), null));
-                        }
+                        reply.reply(codec.encodeErrorEnvelope(errorCode, errorMessage, errorDetails));
                     }
 
                     @Override
@@ -228,7 +206,7 @@ public final class MethodChannel {
                 });
             } catch (RuntimeException e) {
                 Log.e(TAG + name, "Failed to handle method call", e);
-                reply.reply(codec.encodeErrorEnvelope("uncaught", e.getMessage(), null));
+                reply.reply(codec.encodeErrorEnvelope("error", e.getMessage(), null));
             }
         }
     }

shell/platform/darwin/ios/framework/Source/FlutterCodecs.mm

@@ -57,7 +57,17 @@
 - (NSData*)encode:(id)message {
   if (message == nil)
     return nil;
-  NSData* encoding = [NSJSONSerialization dataWithJSONObject:message options:0 error:nil];
+  NSData* encoding;
+  if ([message isKindOfClass:[NSArray class]] || [message isKindOfClass:[NSDictionary class]]) {
+    encoding = [NSJSONSerialization dataWithJSONObject:message options:0 error:nil];
+  } else {
+    // NSJSONSerialization does not support top-level simple values.
+    // We encode as singleton array, then extract the relevant bytes.
+    encoding = [NSJSONSerialization dataWithJSONObject:@[message] options:0 error:nil];
+    if (encoding) {
+      encoding = [encoding subdataWithRange:NSMakeRange(1, encoding.length - 2)];
+    }
+  }
   NSAssert(encoding, @"Invalid JSON message, encoding failed");
   return encoding;
 }
@@ -65,9 +75,28 @@
 - (id)decode:(NSData*)message {
   if (message == nil)
     return nil;
-  id decoded = [NSJSONSerialization JSONObjectWithData:message options:0 error:nil];
+  BOOL isSimpleValue = NO;
+  id decoded = nil;
+  if (0 < message.length) {
+    UInt8 first;
+    [message getBytes:&first length:1];
+    isSimpleValue = first != '{' && first != '[';
+    if (isSimpleValue) {
+      // NSJSONSerialization does not support top-level simple values.
+      // We expand encoding to singleton array, then decode that and extract
+      // the single entry.
+      UInt8 begin = '[';
+      UInt8 end = ']';
+      NSMutableData* expandedMessage = [NSMutableData dataWithLength:message.length + 2];
+      [expandedMessage replaceBytesInRange:NSMakeRange(0, 1) withBytes:&begin];
+      [expandedMessage replaceBytesInRange:NSMakeRange(1, message.length) withBytes:message.bytes];
+      [expandedMessage replaceBytesInRange:NSMakeRange(message.length + 1, 1) withBytes:&end];
+      message = expandedMessage;
+    }
+    decoded = [NSJSONSerialization JSONObjectWithData:message options:0 error:nil];
+  }
   NSAssert(decoded, @"Invalid JSON message, decoding failed");
-  return decoded;
+  return isSimpleValue ? ((NSArray*) decoded)[0] : decoded;
 }
 @end
 
@@ -83,27 +112,26 @@
 - (NSData*)encodeMethodCall:(FlutterMethodCall*)call {
   return [[FlutterJSONMessageCodec sharedInstance] encode:@{
     @"method" : call.method,
-    @"args" : (call.arguments == nil ? [NSNull null] : call.arguments),
+    @"args" : [self wrapNil:call.arguments],
   }];
 }
 
 - (NSData*)encodeSuccessEnvelope:(id)result {
-  return
-      [[FlutterJSONMessageCodec sharedInstance] encode:@[ result == nil ? [NSNull null] : result ]];
+  return [[FlutterJSONMessageCodec sharedInstance] encode:@[[self wrapNil:result]]];
 }
 
 - (NSData*)encodeErrorEnvelope:(FlutterError*)error {
   return [[FlutterJSONMessageCodec sharedInstance] encode:@[
     error.code,
-    error.message == nil ? [NSNull null] : error.message,
-    error.details == nil ? [NSNull null] : error.details,
+    [self wrapNil:error.message],
+    [self wrapNil:error.details],
   ]];
 }
 
 - (FlutterMethodCall*)decodeMethodCall:(NSData*)message {
   NSDictionary* dictionary = [[FlutterJSONMessageCodec sharedInstance] decode:message];
   id method = dictionary[@"method"];
-  id arguments = dictionary[@"args"];
+  id arguments = [self unwrapNil:dictionary[@"args"]];
   NSAssert([method isKindOfClass:[NSString class]], @"Invalid JSON method call");
   return [FlutterMethodCall methodCallWithMethodName:method arguments:arguments];
 }
@@ -111,10 +139,20 @@
 - (id)decodeEnvelope:(NSData*)envelope {
   NSArray* array = [[FlutterJSONMessageCodec sharedInstance] decode:envelope];
   if (array.count == 1)
-    return array[0];
+    return [self unwrapNil:array[0]];
   NSAssert(array.count == 3, @"Invalid JSON envelope");
-  NSAssert([array[0] isKindOfClass:[NSString class]], @"Invalid JSON envelope");
-  NSAssert(array[1] == nil || [array[1] isKindOfClass:[NSString class]], @"Invalid JSON envelope");
-  return [FlutterError errorWithCode:array[0] message:array[1] details:array[2]];
+  id code = array[0];
+  id message = [self unwrapNil:array[1]];
+  id details = [self unwrapNil:array[2]];
+  NSAssert([code isKindOfClass:[NSString class]], @"Invalid JSON envelope");
+  NSAssert(message == nil || [message isKindOfClass:[NSString class]], @"Invalid JSON envelope");
+  return [FlutterError errorWithCode:code message:message details:details];
+}
+
+- (id)wrapNil:(id)value {
+  return value == nil ? [NSNull null] : value;
+}
+- (id)unwrapNil:(id)value {
+  return value == [NSNull null] ? nil : value;
 }
 @end