[inspector] introduced stepIntoAsync for chained callbacks

src/js/promise.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, extrasUtils) {
 
 "use strict";
 
 %CheckIsBootstrapping();
 
@@ skipping 31 matching lines @@
   // trigger redundant ExceptionEvents
   var deferred = %new_promise_capability(this, false);
   var resolutions = new InternalArray();
   var count;
 
   // For catch prediction, don't treat the .then calls as handling it;
   // instead, recurse outwards.
   var instrumenting = DEBUG_IS_ACTIVE;
   if (instrumenting) {
     SET_PRIVATE(deferred.reject, promiseForwardingHandlerSymbol, true);
+    %DebugSetNonBreakableAsyncEvents(true);

[Yang, 2017/01/30 13:30:14]

This is not particular elegant. Especially if PromiseAll is called recursively.

I think what you should rather do is to mark the SharedFunctionInfo for
PromiseAll and PromiseRace with a new debugger_hints flag. When you then iterate
the stack, and find a function with that flag, you know that a non-breakable
async event is on-going.

[kozy, 2017/01/30 16:58:00]

Done.

   }
 
   function CreateResolveElementFunction(index, values, promiseCapability) {
     var alreadyCalled = false;
     return (x) => {
       if (alreadyCalled === true) return;
       alreadyCalled = true;
       values[index] = x;
       if (--count === 0) {
         var valuesArray = [];
@@ skipping 23 matching lines @@
     // 6.d
     if (--count === 0) {
       var valuesArray = [];
       %MoveArrayContents(resolutions, valuesArray);
       %_Call(deferred.resolve, UNDEFINED, valuesArray);
     }
 
   } catch (e) {
     %_Call(deferred.reject, UNDEFINED, e);
   }
+  if (instrumenting) {
+    %DebugSetNonBreakableAsyncEvents(false);
+  }
   return deferred.promise;
 }
 
 // ES#sec-promise.race
 // Promise.race ( iterable )
 function PromiseRace(iterable) {
   if (!IS_RECEIVER(this)) {
     throw %make_type_error(kCalledOnNonObject, PromiseRace);
   }
 
   // false debugEvent so that forwarding the rejection through race does not
   // trigger redundant ExceptionEvents
   var deferred = %new_promise_capability(this, false);
 
   // For catch prediction, don't treat the .then calls as handling it;
   // instead, recurse outwards.
   var instrumenting = DEBUG_IS_ACTIVE;
   if (instrumenting) {
     SET_PRIVATE(deferred.reject, promiseForwardingHandlerSymbol, true);
+    %DebugSetNonBreakableAsyncEvents(true);
   }
 
   try {
     for (var value of iterable) {
       var throwawayPromise = this.resolve(value).then(deferred.resolve,
                                                       deferred.reject);
       // For catch prediction, mark that rejections here are semantically
       // handled by the combined Promise.
       if (instrumenting && %is_promise(throwawayPromise)) {
         SET_PRIVATE(throwawayPromise, promiseHandledBySymbol, deferred.promise);
       }
     }
   } catch (e) {
     %_Call(deferred.reject, UNDEFINED, e);
   }
+  if (instrumenting) {
+    %DebugSetNonBreakableAsyncEvents(false);
+  }
   return deferred.promise;
 }
 
 // -------------------------------------------------------------------
 // Install exported functions.
 
 utils.InstallFunctions(GlobalPromise, DONT_ENUM, [
   "all", PromiseAll,
   "race", PromiseRace,
 ]);
 
 %InstallToContext([
   "promise_id_resolve_handler", PromiseIdResolveHandler,
   "promise_id_reject_handler", PromiseIdRejectHandler
 ]);
 
 })