A brutal approach to V8 script liveedit

src/debug-delay.js

 // Copyright 2006-2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 727 matching lines @@
 };
 
 
 // Get all the scripts currently loaded. Locating all the scripts is based on
 // scanning the heap.
 Debug.scripts = function() {
   // Collect all scripts in the heap.
   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);
 }
 
 function ExecutionState(break_id) {
   this.break_id = break_id;
   this.selected_frame = 0;
 }
 
 ExecutionState.prototype.prepareStep = function(opt_action, opt_count) {
@@ skipping 481 matching lines @@
         this.sourceRequest_(request, response);
       } else if (request.command == 'scripts') {
         this.scriptsRequest_(request, response);
       } else if (request.command == 'threads') {
         this.threadsRequest_(request, response);
       } else if (request.command == 'suspend') {
         this.suspendRequest_(request, response);
       } 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');
       }
     } catch (e) {
       // If there is no response object created one (without command).
       if (!response) {
         response = this.createResponse();
       }
       response.success = false;
       response.message = %ToString(e);
@@ skipping 682 matching lines @@
     %ProfilerResume(modules, tag);
   } else if (request.arguments.command == 'pause') {
     %ProfilerPause(modules, tag);
   } else {
     return response.failed('Unknown command');
   }
   response.body = {};
 };
 
 
+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() {
   return this.running_;
 }
 
 
 DebugCommandProcessor.prototype.systemBreak = function(cmd, args) {
   return %SystemBreak();
 };
@@ skipping 106 matching lines @@
     case 'string':
     case 'number':
       json = value;
       break
 
     default:
       json = null;
   }
   return json;
 }