[wasm] Clean up test case

src/js/messages.js

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // -------------------------------------------------------------------
 
 (function(global, utils) {
 
 %CheckIsBootstrapping();
 
@@ skipping 614 matching lines @@
 function CallSiteGetScriptNameOrSourceURL() {
   CheckCallSite(this, "getScriptNameOrSourceURL");
   return %CallSiteGetScriptNameOrSourceUrlRT(this);
 }
 
 function CallSiteGetFunctionName() {
   // See if the function knows its own name
   CheckCallSite(this, "getFunctionName");
   if (HAS_PRIVATE(this, callSiteWasmObjectSymbol)) {
     var wasm = GET_PRIVATE(this, callSiteWasmObjectSymbol);
+    if (IS_UNDEFINED(wasm)) return "<WASM>";
     var func_index = GET_PRIVATE(this, callSiteWasmFunctionIndexSymbol);
-    if (IS_UNDEFINED(wasm)) return "<WASM>";
-    return %WasmGetFunctionName(wasm, func_index);
+    var func_name = %WasmGetFunctionName(wasm, func_index);
+    return func_name ? func_name : "<WASM>";

[Yang, 2016/05/09 05:34:55]

Can we do a IS_UNDEFINED check if we only expect undefined or strings?

[clemensh, 2016/05/09 07:38:46]

Unfortunately not. At least not without further changes in the way function
names are stored inside the wasm modules. It does not distinguish currently
between "no name" and "empty name". So we always get an empty string if no name
was set, and only get undefined if e.g. the string is no valid UTF-8.

[Yang, 2016/05/11 05:49:41]

I see. Can we hide this logic inside %WasmGetFunctionName? I'd like to avoid
implicit conversions, and it should be the job of the wasm part of V8 to deliver
the appropriate name.

   }
   return %CallSiteGetFunctionNameRT(this);
 }
 
 function CallSiteGetMethodName() {
   // See if we can find a unique property on the receiver that holds
   // this function.
   CheckCallSite(this, "getMethodName");
   return %CallSiteGetMethodNameRT(this);
 }
@@ skipping 394 matching lines @@
 utils.Export(function(to) {
   to.ErrorToString = ErrorToString;
   to.MakeError = MakeError;
   to.MakeRangeError = MakeRangeError;
   to.MakeSyntaxError = MakeSyntaxError;
   to.MakeTypeError = MakeTypeError;
   to.MakeURIError = MakeURIError;
 });
 
 });