Support stepping into generator function.

R=aandrey@chromium.org, wingo@igalia.com
BUG=v8:3572
LOG=Y

Review URL: https://codereview.chromium.org/544953005

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24000 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/generator.js

@@ -20,6 +20,7 @@ function GeneratorObjectNext(value) {
                         ['[Generator].prototype.next', this]);
   }
 
+  if (DEBUG_IS_ACTIVE) %DebugPrepareStepInIfStepping(this);
   return %_GeneratorNext(this, value);
 }
 

src/runtime.cc

@@ -5524,13 +5524,22 @@ RUNTIME_FUNCTION(Runtime_DebugPrepareStepInIfStepping) {
   DCHECK(args.length() == 1);
   Debug* debug = isolate->debug();
   if (!debug->IsStepping()) return isolate->heap()->undefined_value();
-  CONVERT_ARG_HANDLE_CHECKED(JSFunction, callback, 0);
+
   HandleScope scope(isolate);
-  // When leaving the callback, step out has been activated, but not performed
-  // if we do not leave the builtin.  To be able to step into the callback
+  CONVERT_ARG_HANDLE_CHECKED(Object, object, 0);
+  RUNTIME_ASSERT(object->IsJSFunction() || object->IsJSGeneratorObject());
+  Handle<JSFunction> fun;
+  if (object->IsJSFunction()) {
+    fun = Handle<JSFunction>::cast(object);
+  } else {
+    fun = Handle<JSFunction>(
+        Handle<JSGeneratorObject>::cast(object)->function(), isolate);
+  }
+  // When leaving the function, step out has been activated, but not performed
+  // if we do not leave the builtin.  To be able to step into the function
   // again, we need to clear the step out at this point.
   debug->ClearStepOut();
-  debug->FloodWithOneShot(callback);
+  debug->FloodWithOneShot(fun);
   return isolate->heap()->undefined_value();
 }
 

test/mjsunit/es6/debug-stepin-generators.js

+// Copyright 2014 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.
+
+// Flags: --expose-debug-as debug
+
+Debug = debug.Debug
+var exception = null;
+var yields = 0;
+
+function listener(event, exec_state, event_data, data) {
+  if (event != Debug.DebugEvent.Break) return;
+  try {
+    var source = exec_state.frame(0).sourceLineText();
+    print(source);
+    if (/stop stepping/.test(source)) return;
+    if (/yield/.test(source)) yields++;
+    exec_state.prepareStep(Debug.StepAction.StepIn, 1);
+  } catch (e) {
+    print(e, e.stack);
+    exception = e;
+  }
+};
+
+Debug.setListener(listener);
+
+function* g() {
+  for (var i = 0; i < 3; ++i) {
+    yield i;
+  }
+}
+
+var i = g();
+debugger;
+for (var num of g()) {}
+i.next();
+
+print(); // stop stepping
+
+// Not stepped into.
+i.next();
+i.next();
+
+assertNull(exception);
+assertEquals(4, yields);