A brutal approach to V8 script liveedit

test/mjsunit/debug-liveedit-2.js

Index: test/mjsunit/debug-liveedit-2.js
diff --git a/test/mjsunit/debug-liveedit-2.js b/test/mjsunit/debug-liveedit-2.js
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+// Flags: --expose-debug-as debug
+// Get the Debug object exposed from the debug context global object.
+
+Debug = debug.Debug
+
+eval(
+    "function ChooseAnimal(p) { " +
+    "  if (p == 7) {" + // Use p
+    "    return;" +
+    "  }" +
+    "  return function Chooser() {" +
+    "    return 'Cat';" +
+    "  };" +
+    "}"
+);
+
+var old_closure = ChooseAnimal(19);
+
+assertEquals("Cat", old_closure());
+
+var script = Debug.findScript(ChooseAnimal);
+
+var orig_animal = "'Cat'";
+var patch_pos = script.source.indexOf(orig_animal);
+var new_animal_patch = "'Capybara' + p";
+
+// We patch innermost function "Chooser".
+// However, this does not actually patch existing "Chooser" instances,
+// because old value of parameter "p" was not saved.
+// Instead it patches ChooseAnimal.
+Debug.change_script_live(script, patch_pos, orig_animal.length, new_animal_patch);
+
+var new_closure = ChooseAnimal(19);
+// New instance of closure is patched.
+assertEquals("Capybara19", new_closure());
+
+// Old instance of closure is not patched.
+assertEquals("Cat", old_closure());
+