A brutal approach to V8 script liveedit

src/debug-delay.js

Index: src/debug-delay.js
diff --git a/src/debug-delay.js b/src/debug-delay.js
index 754ac5d0480b1f3e249204edfc42244638e8ec44..55ccdae370a322829c31a6b9ac7c73322ec75ae6 100644
--- a/src/debug-delay.js
+++ b/src/debug-delay.js
@@ -745,6 +745,13 @@ Debug.scripts = function() {
   return %DebugGetLoadedScripts();
 }
 
+// Applies patch to existing script. All relevant functions get recompiled
+// on the best effort basis.
+Debug.change_script_live = function(script, change_pos, change_len, new_str) {
+  %DebugChangeScriptLive(script, change_pos, change_len, new_str);
+}
+
+
 function MakeExecutionState(break_id) {
   return new ExecutionState(break_id);
 }
@@ -1246,7 +1253,9 @@ DebugCommandProcessor.prototype.processDebugJSONRequest = function(json_request)
       } else if (request.command == 'version') {
         this.versionRequest_(request, response);
       } else if (request.command == 'profile') {
-        this.profileRequest_(request, response);
+          this.profileRequest_(request, response);
+      } else if (request.command == 'changelive') {
+          this.changeLiveRequest_(request, response);
       } else {
         throw new Error('Unknown command "' + request.command + '" in request');
       }
@@ -1949,6 +1958,38 @@ DebugCommandProcessor.prototype.profileRequest_ = function(request, response) {
 };
 
 
+DebugCommandProcessor.prototype.changeLiveRequest_ = function(request, response) {
+  if (!request.arguments) {
+    return response.failed('Missing arguments');
+  }
+  var script_id = request.arguments.script_id;
+  var change_pos = parseInt(request.arguments.change_pos);
+  var change_len = parseInt(request.arguments.change_len);
+  var new_string = request.arguments.new_string;
+  if (!IS_STRING(new_string)) {
+    response.failed('Argument "new_string" is not a string value');
+    return;
+  }
+  
+  var scripts = %DebugGetLoadedScripts();
+
+  var the_script = null;
+  for (var i = 0; i < scripts.length; i++) {
+    if (scripts[i].id == script_id) {
+      the_script = scripts[i];
+    }
+  }
+  if (!the_script) {
+    response.failed('Script not found by id');
+    return;
+  }
+  
+  Debug.change_script_live(the_script, change_pos, change_len, new_string);
+	  
+  response.body = {};
+};
+
+
 // Check whether the previously processed command caused the VM to become
 // running.
 DebugCommandProcessor.prototype.isRunning = function() {