Avoid catching listener exceptions in Connection class

src/api/common/connection.js

@@ -24,14 +24,14 @@ class Connection extends EventEmitter {
     this._nextRequestID = 1;
   }
 
-  _onMessage(message) {
+  // return value is array of arguments to Connection.emit
-    try {
+  _parseMessage(message) {
     const data = JSON.parse(message);
     if (data.type === 'response') {
       if (!(Number.isInteger(data.id) && data.id >= 0)) {
         throw new UnexpectedError('valid id not found in response');
       }
-        this.emit(data.id.toString(), data);
+      return [data.id.toString(), data];
     } else if (isStreamMessageType(data.type)) {
       if (data.type === 'ledgerClosed') {
         this._ledgerVersion = Number(data.ledger_index);
@@ -39,15 +39,24 @@ class Connection extends EventEmitter {
         this._availableLedgerVersions.parseAndAddRanges(
           data.validated_ledgers);
       }
-        this.emit(data.type, data);
+      return [data.type, data];
     } else if (data.type === undefined && data.error) {
-        this.emit('error', data.error, data.error_message);  // e.g. slowDown
+      return ['error', data.error, data.error_message];  // e.g. slowDown
-      } else {
+    }
     throw new UnexpectedError('unrecognized message type: ' + data.type);
   }
+
+  _onMessage(message) {
+    let parameters;
+    try {
+      parameters = this._parseMessage(message);
     } catch (error) {
       this.emit('error', 'badMessage', message);
+      return;
     }
+    // we don't want this inside the try/catch or exceptions in listener
+    // will be caught
+    this.emit.apply(this, parameters);
   }
 
   get state() {