Introduce remote objects in Debugger protocol

tools/ddbg.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.
 
 // Simple interactive debugger shell that connects to the Dart VM's debugger
 // connection port.
 
 #import("dart:io");
 #import("dart:json");
 
 Map<int, Completer> outstandingCommands;
 
 Socket vmSock;
 OutputStream vmStream;
 int seqNum = 0;
 
 bool verbose = false;
 
+// The current stack trace, while the VM is paused. It's a list
+// of activation frames.
+List stackTrace;
+
+// The current activation frame, while the VM is paused.
+Map curFrame;
+
 
 void printHelp() {
   print("""
   q   Quit debugger shell
   bt  Show backtrace
   r   Resume execution
   s   Single step
   so  Step over
   si  Step into
-  sbp <file> <line> Set breakpoint
+  sbp [<file>] <line> Set breakpoint
+  po <id> Print object

[siva, 2012/05/22 01:49:09]

missing help for command 'pc' ?

Also noticed 'h' is not listed here.

[hausner, 2012/05/22 18:03:57]

Done.

   ll  List loaded libraries
   ls <libname> List loaded scripts in library
 """);
 }
 
 
 void quitShell() {
   vmStream.close();
   vmSock.close();
   stdin.close();
@@ skipping 16 matching lines @@
 void processCommand(String cmdLine) {
   seqNum++;
   var args = cmdLine.split(' ');
   if (args.length == 0) {
     return;
   }
   var cmd = args[0];
   if (cmd == "r") {
     var cmd = { "id": seqNum, "command": "resume" };
     sendCmd(cmd).then((result) => handleGenericResponse(result));
+    stackTrace = curFrame = null;
   } else if (cmd == "s") {
     var cmd = { "id": seqNum, "command": "stepOver" };
     sendCmd(cmd).then((result) => handleGenericResponse(result));
+    stackTrace = curFrame = null;
   } else if (cmd == "si") {
     var cmd = { "id": seqNum, "command": "stepInto" };
     sendCmd(cmd).then((result) => handleGenericResponse(result));
+    stackTrace = curFrame = null;
   } else if (cmd == "so") {
     var cmd = { "id": seqNum, "command": "stepOut" };
     sendCmd(cmd).then((result) => handleGenericResponse(result));
+    stackTrace = curFrame = null;
   } else if (cmd == "bt") {
     var cmd = { "id": seqNum, "command": "getStackTrace" };
     sendCmd(cmd).then((result) => handleStackTraceResponse(result));
   } else if (cmd == "ll") {
     var cmd = { "id": seqNum, "command": "getLibraryURLs" };
     sendCmd(cmd).then((result) => handleGetLibraryResponse(result));
-  } else if (cmd == "sbp") {
-    if (args.length < 3) {
-      return;
+  } else if (cmd == "sbp" && args.length >= 2) {
+    var url, line;
+    if (args.length == 2) {
+      url = stackTrace[0]["location"]["url"];
+      line = Math.parseInt(args[1]);
+    } else {
+      url = args[1];
+      line = Math.parseInt(args[2]);
     }
     var cmd = { "id": seqNum,
                 "command": "setBreakpoint",
-                "params": { "url": args[1], "line": Math.parseInt(args[2]) }};
+                "params": { "url": url, "line": line }};
     sendCmd(cmd).then((result) => handleSetBpResponse(result));
-  } else if (cmd == "ls") {
-    if (args.length < 2) {
-      return;
-    }
+  } else if (cmd == "ls" && args.length == 2) {
     var cmd = { "id": seqNum,
                  "command": "getScriptURLs",
                 "params": { "library": args[1] }};
     sendCmd(cmd).then((result) => handleGetScriptsResponse(result));
+  } else if (cmd == "po" && args.length == 2) {
+    var cmd = { "id": seqNum, "command": "getObjectProperties",
+                "params": {"objectId": Math.parseInt(args[1]) }};
+    sendCmd(cmd).then((result) => handleGetObjPropsResponse(result));
+  } else if (cmd == "pc" && args.length == 2) {
+    var cmd = { "id": seqNum, "command": "getClassProperties",
+                "params": {"classId": Math.parseInt(args[1]) }};
+    sendCmd(cmd).then((result) => handleGetClassPropsResponse(result));
   } else if (cmd == "q") {
     quitShell();
   } else if (cmd == "h") {
     printHelp();
   } else {
     print("command '$cmd' not understood, try h for help");
   }
 }
 
 
+printNamedObject(obj) {
+  var name = obj["name"];
+  var value = obj["value"];
+  var kind = value["kind"];
+  var text = value["text"];
+  var id = value["objectId"];
+  if (kind == "string") {
+    print("  $name = '$text'");
+  } else if (kind == "object") {
+    print("  $name (id:$id) = $text");
+  } else {
+    print("  $name = $text");
+  }
+}
+
+
+handleGetObjPropsResponse(response) {
+  var props = response["result"];
+  assert(props != null);
+  var class_id = props["classId"];
+  assert(class_id != null);
+  var fields = props["fields"];
+  assert(fields != null);

[siva, 2012/05/22 01:49:09]

Just curious, what is the point of this assert, woudn't we get a
NullPointerException anyway if it turns out to be null.

[hausner, 2012/05/22 18:03:57]

I guess so. Old C++ habits...

+  assert(fields is List);

[siva, 2012/05/22 01:49:09]

Also what is the style here? instead of adding our own type check asserts in
this case does it make sense to code as:
List fields = props["fields"];

[hausner, 2012/05/22 18:03:57]

This is my early code in which I was experimenting. Cleaning it up.

+  print("  class id: $class_id");
+  for (int i = 0; i < fields.length; i++) {
+    printNamedObject(fields[i]);
+  }
+}
+
+
+handleGetClassPropsResponse(response) {
+  var props = response["result"];
+  assert(props != null);
+  assert(props["name"] != null);
+  var libId = props["libraryId"];
+  assert(libId != null);
+  print("  class ${props["name"]} (library id: $libId)");
+  var fields = props["fields"];
+  assert(fields != null);
+  assert(fields is List);
+  if (fields.length > 0) {
+    print("  static fields:");
+    for (int i = 0; i < fields.length; i++) {
+      printNamedObject(fields[i]);
+    }
+  }
+}
+
+
 void handleGetLibraryResponse(response) {
   var result = response["result"];
   assert(result != null);
   var urls = result["urls"];
   assert(urls != null);
   assert(urls is List);
   print("Loaded libraries:");
   for (int i = 0; i < urls.length; i++) {
     print("  $i ${urls[i]}");
   }
@@ skipping 27 matching lines @@
     print("Error: ${response["error"]}");
   }
 }
 
 
 void handleStackTraceResponse(response) {
   var result = response["result"];
   assert(result != null);
   var callFrames = result["callFrames"];
   assert(callFrames != null);
-  printStackTrace(result);
+  printStackTrace(callFrames);
 }
 
 
-void printStackTrace(trace) {
-  assert(trace != null);
-  var frames = trace["callFrames"];
-  if (frames is !List) {
-    print("unexpected type for frames parameter $frames");
-    return;
+void printStackFrame(frame_num, frame) {
+  var fname = frame["functionName"];
+  var url = frame["location"]["url"];
+  var line = frame["location"]["lineNumber"];
+  print("$frame_num  $fname ($url:$line)");
+  var locals = frame["locals"];
+  assert(locals is List);

[siva, 2012/05/22 01:49:09]

Ditto question about explicit type check assert.

[hausner, 2012/05/22 18:03:57]

Done.

+  for (int i = 0; i < locals.length; i++) {
+    printNamedObject(locals[i]);
   }
+}
+
+
+void printStackTrace(List frames) {
   for (int i = 0; i < frames.length; i++) {
-    var frame = frames[i];
-    var fname = frame["functionName"];
-    var url = frame["location"]["url"];
-    var line = frame["location"]["lineNumber"];
-    print("$i  $fname ($url:$line)");
+    printStackFrame(i, frames[i]);
   }
 }
 
 
+void handlePausedEvent(msg) {
+  assert(msg["params"] != null);
+  stackTrace = msg["params"]["callFrames"];
+  assert(stackTrace != null);
+  assert(stackTrace.length >= 1);
+  curFrame = stackTrace[0];
+  print("VM paused, stack trace:");
+  printStackTrace(stackTrace);
+}
+
+
 void processVmMessage(String json) {
   var msg = JSON.parse(json);
   if (msg == null) {
     return;
   }
   var event = msg["event"];
   if (event == "paused") {
-    print("VM paused, stack trace:");
-    printStackTrace(msg["params"]);
+    handlePausedEvent(msg);
     return;
   }
   if (event == "breakpointResolved") {
     var params = msg["params"];
     assert(params != null);
     print("BP ${params["breakpointId"]} resolved and "
           "set at line ${params["line"]}.");
     return;
   }
   if (msg["id"] != null) {
@@ skipping 54 matching lines @@
   };
   vmInStream.onError = (err) {
     print("Error in debug connection: $err");
     quitShell();
   };
   vmInStream.onClosed = () {
     print("VM debugger connection closed");
     quitShell();
   };
 }