Bug 974546 - SpecialPowers wrappers should catch, wrap, and rethrow exceptions for callables. r=mrbkap

testing/mochitest/tests/test_SpecialPowersExtension.html

@@ -141,6 +141,24 @@ function starttest(){
   var returnsNull = function() { return null; }
   is(SpecialPowers.wrap(returnsNull)(), null, "Should be able to handle functions that return null.");
 
+  // Check a function that throws.
+  var thrower = function() { throw new Error('hah'); }
+  try {
+    SpecialPowers.wrap(thrower)();
+    ok(false, "Should have thrown");
+  } catch (e) {
+    ok(SpecialPowers.isWrapper(e), "Exceptions should be wrapped for call");
+    is(e.message, 'hah', "Correct message");
+  }
+  try {
+    var ctor = SpecialPowers.wrap(thrower);
+    new ctor();
+    ok(false, "Should have thrown");
+  } catch (e) {
+    ok(SpecialPowers.isWrapper(e), "Exceptions should be wrapped for construct");
+    is(e.message, 'hah', "Correct message");
+  }
+
   // Play around with a JS object to check the non-xray path.
   var noxray_proto = {a: 3, b: 12};
   var noxray = {a: 5, c: 32};

testing/specialpowers/content/specialpowersAPI.js

@@ -115,7 +115,12 @@ function wrapPrivileged(obj) {
       var invocant = unwrapIfWrapped(this);
       var unwrappedArgs = Array.prototype.slice.call(arguments).map(unwrapIfWrapped);
 
-      return wrapPrivileged(doApply(obj, invocant, unwrappedArgs));
+      try {
+        return wrapPrivileged(doApply(obj, invocant, unwrappedArgs));
+      } catch (e) {
+        // Wrap exceptions and re-throw them.
+        throw wrapIfUnwrapped(e);
+      }
     };
     var constructTrap = function() {
       // The arguments may or may not be wrappers. Unwrap them if necessary.
@@ -129,7 +134,12 @@ function wrapPrivileged(obj) {
       // underlying constructor just be passing along its return value in our
       // constructor.
       var FakeConstructor = function() {
-        return doApply(obj, this, unwrappedArgs);
+        try {
+          return doApply(obj, this, unwrappedArgs);
+        } catch (e) {
+          // Wrap exceptions and re-throw them.
+          throw wrapIfUnwrapped(e);
+        }
       };
       FakeConstructor.prototype = obj.prototype;