Workaround IE's defficient handling of finally statements in Periodic…

…alExecuter. [#696 state:resolved]
prototypejs · Jul 21, 2009 · 49090bc · 49090bc
1 parent e41ccba
commit 49090bc
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diff --git a/CHANGELOG b/CHANGELOG
@@ -1,4 +1,4 @@
-* Re-throw error in otherwise-empty `catch` clause so that `PeriodicalExecuter` does not suppress exceptions. (Samuel Lebeau)
+* Fix `PeriodicalExecuter` so that it no longer suppresses exceptions. [#696 state:resolved] (Samuel Lebeau, Yaffle)
 
 * Fix issue related to escaping of selectors for querySelectorAll. [#559 state:resolved] (Jorn Holm)
 

diff --git a/src/lang/periodical_executer.js b/src/lang/periodical_executer.js
@@ -49,15 +49,20 @@ var PeriodicalExecuter = Class.create({
 
   onTimerEvent: function() {
     if (!this.currentlyExecuting) {
-      try {
-        this.currentlyExecuting = true;
-        this.execute();
-      } catch(e) {
-        // Catch clause for clients that don't support try/finally.
-        throw e;
-      }
-      finally {
-        this.currentlyExecuting = false;
+      if (!this.currentlyExecuting) {
+        // IE doesn't support `finally` statements unless all errors are caught.
+        // We mimic the behaviour of `finally` statements by duplicating code
+        // that would belong in it. First at the bottom of the `try` statement
+        // (for errorless cases). Secondly, inside a `catch` statement which
+        // rethrows any caught errors.
+        try {
+          this.currentlyExecuting = true;
+          this.execute();
+          this.currentlyExecuting = false;
+        } catch(e) {
+          this.currentlyExecuting = false;
+          throw e;
+        }
       }
     }
   }