Fix duplicate logs from scripts when ext is used

lib/sandbox.js

@@ -193,6 +193,7 @@ function commit() {
 
 
 function ext() {
+  ++ state.extCounter;
   let extCall = Array.from(arguments).map(String);
   let key = `${state.revision}: ${JSON.stringify(extCall)}`;
 
@@ -205,7 +206,7 @@ function ext() {
 
 
 function log(msg, meta) {
-  if (state.revision === state.maxRevision) {
+  if (state.revision === state.maxRevision && state.extCounter >= 0) {
     const details = Object.assign({}, meta, {
       sessionContext: state.sessionContext,
       message: `Script: ${msg}`
@@ -255,7 +256,7 @@ function errorToFault(err) {
 }
 
 
-function run(script, globals, sessionContext, startRevision, maxRevision, callback) {
+function run(script, globals, sessionContext, startRevision, maxRevision, callback, extCounter = 0) {
   state = {
     sessionContext: sessionContext,
     revision: startRevision,
@@ -264,7 +265,8 @@ function run(script, globals, sessionContext, startRevision, maxRevision, callba
     declarations: [],
     extensions: {},
     clear: [],
-    rng: null
+    rng: null,
+    extCounter: extCounter
   };
 
   for (let n of Object.keys(context))
@@ -288,7 +290,12 @@ function run(script, globals, sessionContext, startRevision, maxRevision, callba
   }
 
   let _state = state;
-  let args = arguments;
+  let args = Array.from(arguments);
+
+  // Need to maintain a counter of ext() calls to avoid calling certain
+  // functions (e.g. log()) multiple times as calling ext() results in
+  // re-execution of script without revision being incremented.
+  args[6] = 0 - (state.extCounter - extCounter);
 
   let counter = 3;
   for (let key of Object.keys(_state.extensions)) {