[inspector] Expose scopes for suspended generator objects

test/inspector/debugger/suspended-generator-scopes.js

+// Copyright 2016 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.
+
+InspectorTest.addScript(
+`function *gen(a) {
+  var b = 42;
+  yield a;
+  return b;
+}
+function testSuspendedGenerator()
+{
+  var g = gen(420);
+  g.next();
+
+  debugger;
+}`);
+
+Protocol.Debugger.enable();
+Protocol.Debugger.oncePaused().then(dumpScopeOnPause);
+Protocol.Runtime.evaluate({ "expression": "testSuspendedGenerator()" });
+
+var waitScopeObjects = 0;
+function dumpScopeOnPause(message)
+{
+  var scopeChain = message.params.callFrames[0].scopeChain;
+  var localScopeObjectIds = [];
+  for (var scope of scopeChain) {
+    if (scope.type === "local")
+      localScopeObjectIds.push(scope.object.objectId);
+  }
+  if (localScopeObjectIds.length != 1) {
+    InspectorTest.completeTest();
+  } else {
+    for (var objectId of localScopeObjectIds)
+      Protocol.Runtime.getProperties({ "objectId" : objectId })
+          .then(fetchGeneratorProperties)
+          .then(dumpGeneratorScopes);
+  }
+}
+
+function fetchGeneratorProperties(msg) {
+  return Protocol.Runtime.getProperties(
+      { objectId : msg.result.result[0].value.objectId });
+}
+
+function dumpGeneratorScopes(msg)
+{
+  var props = msg.result.internalProperties;
+  for (var i = 0; i < props.length; i++) {
+    var prop = props[i];
+    if (prop.name == "[[Scopes]]") {
+      InspectorTest.logMessage(prop);
+      // Print the innermost scopes.
+      Protocol.Runtime.getProperties({ objectId : prop.value.objectId })
+          .then(msg => {
+            var scopes = msg.result.result;
+            InspectorTest.logMessage(scopes);

[jgruber, 2016/11/22 14:57:32]

If we attempt to get the properties of e.g. the innermost scope here, inspector
comes back with an error. I suspect the object is already gone by the time we
try to fetch its details. Any ideas?


            var inner_scope = scopes[0].value;
            print(inner_scope.objectId);
            return Protocol.Runtime.getProperties(
                { objectId : inner_scope.objectId });

-->

{"injectedScriptId":1,"id":29}

{
    error : {
        code : -32000
        message : Could not find object with given id
    }
    id : <messageId>
}

[kozy, 2016/11/22 19:26:37]

I think the problem here that you call Debugger.resume before
Runtime.getProperties is finished. On Debugger.resume we clear "backtrace"
object group that contains all objects related to pause, e.g. scopes.
To check this I wrote test: http://pastebin.com/raw/2gWSNE92 feel free to use
it.

And could you add a test that not on pause we can get scopes too?

+          });
+    }
+  }
+  Protocol.Debugger.resume().then(InspectorTest.completeTest);
+}