Start adding vm/cc tests for rewind functionality.

runtime/vm/json_stream.cc

 // Copyright (c) 2013, 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.
 
 #include "platform/assert.h"
 
 #include "include/dart_native_api.h"
 #include "vm/dart_entry.h"
 #include "vm/debugger.h"
 #include "vm/json_stream.h"
@@ skipping 192 matching lines @@
 
 
 static void Finalizer(void* isolate_callback_data,
                       Dart_WeakPersistentHandle handle,
                       void* buffer) {
   free(buffer);
 }
 
 
 void JSONStream::PostReply() {
+  ASSERT(seq_ != NULL);
   Dart_Port port = reply_port();
-  ASSERT(port != ILLEGAL_PORT);
   set_reply_port(ILLEGAL_PORT);  // Prevent double replies.
-  ASSERT(seq_ != NULL);
   if (seq_->IsString()) {
     const String& str = String::Cast(*seq_);
     PrintProperty("id", str.ToCString());
   } else if (seq_->IsInteger()) {
     const Integer& integer = Integer::Cast(*seq_);
     PrintProperty64("id", integer.AsInt64Value());
   } else if (seq_->IsDouble()) {
     const Double& dbl = Double::Cast(*seq_);
     PrintProperty("id", dbl.value());
   } else if (seq_->IsNull()) {
+    if (port == ILLEGAL_PORT) {
+      // This path is only used in tests.
+      buffer_.AddChar('}');  // Finish our message.
+      char* cstr;
+      intptr_t length;
+      Steal(&cstr, &length);
+      fprintf(stderr, "-----\nDropping reply:\n%s\n-----\n", cstr);

[rmacnak, 2017/01/31 19:21:00]

OS::PrintErr

[turnidge, 2017/01/31 19:35:46]

Done.

+      free(cstr);
+    }
     // JSON-RPC 2.0 says that a request with a null ID shouldn't get a reply.
     PostNullReply(port);
     return;
   }
-  buffer_.AddChar('}');
+  ASSERT(port != ILLEGAL_PORT);
 
+  buffer_.AddChar('}');  // Finish our message.
   char* cstr;
   intptr_t length;
   Steal(&cstr, &length);
 
   bool result;
   {
     TransitionVMToNative transition(Thread::Current());
     Dart_CObject bytes;
     bytes.type = Dart_CObject_kExternalTypedData;
     bytes.value.as_external_typed_data.type = Dart_TypedData_kUint8;
@@ skipping 779 matching lines @@
   ASSERT(len == len2);
   stream_->buffer_.AddChar('"');
   stream_->AddEscapedUTF8String(p);
   stream_->buffer_.AddChar('"');
   free(p);
 }
 
 #endif  // !PRODUCT
 
 }  // namespace dart