Handling exceptions.

I believe this is the most appropriate way to handle exceptions. Using
v8::Function::Call rather than node::MakeCallback (via NanMakeCallback)
means that these functions will not work with domains, but that seems
appropriate.

I don't know if nodejs/node-v0.x-archive#9245 or nodejs/nan#284 should be a concern
here or not.

src/database.cc

@@ -475,10 +475,15 @@ void Database::FunctionExecute(FunctionBaton *baton, FunctionInvocation *invocat
             argv.push_back(arg);
         }
 
-        Local<Value> result = TRY_CATCH_CALL(NanObjectWrapHandle(db), cb, argc, argv.data());
+        TryCatch trycatch;
+        Local<Value> result = cb->Call(NanObjectWrapHandle(db), argc, argv.data());
 
         // process the result
-        if (result->IsString() || result->IsRegExp()) {
+        if (trycatch.HasCaught()) {
+            String::Utf8Value message(trycatch.Message()->Get());
+            sqlite3_result_error(context, *message, message.length());
+        }
+        else if (result->IsString() || result->IsRegExp()) {
             String::Utf8Value value(result->ToString());
             sqlite3_result_text(context, *value, value.length(), SQLITE_TRANSIENT);
         }

test/user_functions.test.js

@@ -77,9 +77,9 @@ describe('user functions', function() {
         });
     });
 
-    it.skip('reports errors thrown in functions', function(done) {
+    it('reports errors thrown in functions', function(done) {
         db.all('SELECT MY_ERROR() AS val', function(err, rows) {
-            assert.equal(err.message, 'This function always throws');
+            assert.equal(err.message, 'SQLITE_ERROR: Uncaught Error: This function always throws');
             assert.equal(rows, undefined);
             done();
         });