- Allow an isolate to be started in paused state.

runtime/lib/isolate_patch.dart

 // Copyright (c) 2012, 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.
 
 import "dart:collection" show HashMap;
 
 patch class ReceivePort {
   /* patch */ factory ReceivePort() = _ReceivePortImpl;
 
   /* patch */ factory ReceivePort.fromRawReceivePort(RawReceivePort rawPort) =
@@ skipping 179 matching lines @@
 typedef _MainFunctionArgs(args);
 typedef _MainFunctionArgsMessage(args, message);
 
 /**
  * Takes the real entry point as argument and invokes it with the
  * initial message.  Defers execution of the entry point until the
  * isolate is in the message loop.
  */
 void _startMainIsolate(Function entryPoint,
                        List<String> args) {
-  RawReceivePort port = new RawReceivePort();
-  port.handler = (_) {
-    port.close();
-    _startIsolate(null,   // no parent port
-                  entryPoint,
-                  args,
-                  null,   // no message
-                  true,   // isSpawnUri
-                  null,   // no control port
-                  null);  // no capabilities
-  };
-  port.sendPort.send(null);
+  _startIsolate(null,   // no parent port
+                entryPoint,
+                args,
+                null,   // no message
+                true,   // isSpawnUri
+                null,   // no control port
+                null);  // no capabilities
 }
 
 /**
  * Takes the real entry point as argument and invokes it with the initial
  * message.
  */
 void _startIsolate(SendPort parentPort,
                    Function entryPoint,
                    List<String> args,
                    var message,
                    bool isSpawnUri,
                    RawReceivePort controlPort,
                    List capabilities) {
+  // The control port (aka the main isolate port) does not handle any messages.
   if (controlPort != null) {
     controlPort.handler = (_) {};  // Nobody home on the control port.
   }
+
   if (parentPort != null) {
     // Build a message to our parent isolate providing access to the
     // current isolate's control port and capabilities.
     //
     // TODO(floitsch): Send an error message if we can't find the entry point.
     var readyMessage = new List(2);
     readyMessage[0] = controlPort.sendPort;
     readyMessage[1] = capabilities;
 
     // Out of an excess of paranoia we clear the capabilities from the
     // stack.  Not really necessary.
     capabilities = null;
     parentPort.send(readyMessage);
   }
   assert(capabilities == null);
 
-  if (isSpawnUri) {
-    if (entryPoint is _MainFunctionArgsMessage) {
-      entryPoint(args, message);
-    } else if (entryPoint is _MainFunctionArgs) {
-      entryPoint(args);
+  // Delay all user code handling to the next run of the message loop. This
+  // allows us to intercept certain conditions in the event dispatch, such as
+  // starting in paused state.
+  RawReceivePort port = new RawReceivePort();
+  port.handler = (_) {
+    port.close();
+
+    if (isSpawnUri) {
+      if (entryPoint is _MainFunctionArgsMessage) {
+        entryPoint(args, message);
+      } else if (entryPoint is _MainFunctionArgs) {
+        entryPoint(args);
+      } else {
+        entryPoint();
+      }
     } else {
-      entryPoint();
+      entryPoint(message);
     }
-  } else {
-    entryPoint(message);
-  }
-  _runPendingImmediateCallback();
+  };
+  // Make sure the message handler is triggered.
+  port.sendPort.send(null);
 }
 
 patch class Isolate {
   static final _currentIsolate = _getCurrentIsolate();
 
   /* patch */ static Isolate get current => _currentIsolate;
 
   /* patch */ static Future<Isolate> spawn(
       void entryPoint(message), var message, { bool paused: false }) {
     // `paused` isn't handled yet.
     RawReceivePort readyPort;
     try {
       // The VM will invoke [_startIsolate] with entryPoint as argument.
       readyPort = new RawReceivePort();
-      _spawnFunction(readyPort.sendPort, entryPoint, message);
+      _spawnFunction(readyPort.sendPort, entryPoint, message, paused);
       Completer completer = new Completer<Isolate>.sync();
       readyPort.handler = (readyMessage) {
         readyPort.close();
         assert(readyMessage is List);
         assert(readyMessage.length == 2);
         SendPort controlPort = readyMessage[0];
         List capabilities = readyMessage[1];
         completer.complete(new Isolate(controlPort,
                                        pauseCapability: capabilities[0],
                                        terminateCapability: capabilities[1]));
@@ skipping 10 matching lines @@
   /* patch */ static Future<Isolate> spawnUri(
       Uri uri, List<String> args, var message,
       { bool paused: false, Uri packageRoot }) {
     // `paused` isn't handled yet.
     RawReceivePort readyPort;
     try {
       // The VM will invoke [_startIsolate] and not `main`.
       readyPort = new RawReceivePort();
       var packageRootString =
           (packageRoot == null) ? null : packageRoot.toString();
-      _spawnUri(
-          readyPort.sendPort, uri.toString(), args, message, packageRootString);
+      _spawnUri(readyPort.sendPort, uri.toString(), args, message,
+                paused, packageRootString);
       Completer completer = new Completer<Isolate>.sync();
       readyPort.handler = (readyMessage) {
         readyPort.close();
         assert(readyMessage is List);
         assert(readyMessage.length == 2);
         SendPort controlPort = readyMessage[0];
         List capabilities = readyMessage[1];
         completer.complete(new Isolate(controlPort,
                                        pauseCapability: capabilities[0],
                                        terminateCapability: capabilities[1]));
@@ skipping 11 matching lines @@
   // TODO(iposva): Cleanup to have only one definition.
   // These values need to be kept in sync with the class IsolateMessageHandler
   // in vm/isolate.cc.
   static const _PAUSE = 1;
   static const _RESUME = 2;
   static const _PING = 3;
   static const _KILL = 4;
 
 
   static SendPort _spawnFunction(SendPort readyPort, Function topLevelFunction,
-                                 var message)
+                                 var message, bool paused)
       native "Isolate_spawnFunction";
 
   static SendPort _spawnUri(SendPort readyPort, String uri,
                             List<String> args, var message,
-                            String packageRoot)
+                            bool paused, String packageRoot)
       native "Isolate_spawnUri";
 
   static void _sendOOB(port, msg) native "Isolate_sendOOB";
 
   /* patch */ void _pause(Capability resumeCapability) {
     var msg = new List(4)
         ..[0] = 0  // Make room for OOB message type.
         ..[1] = _PAUSE
         ..[2] = pauseCapability
         ..[3] = resumeCapability;
@@ skipping 50 matching lines @@
   static Isolate _getCurrentIsolate() {
     List portAndCapabilities = _getPortAndCapabilitiesOfCurrentIsolate();
     return new Isolate(portAndCapabilities[0],
                        pauseCapability: portAndCapabilities[1],
                        terminateCapability: portAndCapabilities[2]);
   }
 
   static List _getPortAndCapabilitiesOfCurrentIsolate()
       native "Isolate_getPortAndCapabilitiesOfCurrentIsolate";
 }