refact: Output error trace when callback execution fails (#212)

Author: oakbani

.rubocop.yml

@@ -47,3 +47,6 @@ Style/SignalException:
 
 Lint/RescueException:
   Enabled: false
+
+Layout/EndOfLine:
+  EnforcedStyle: lf

lib/optimizely/config_manager/async_scheduler.rb

@@ -75,10 +75,10 @@ def execution_wrapper(callback)
       loop do
         begin
           callback.call
-        rescue
+        rescue StandardError => e
           @logger.log(
             Logger::ERROR,
-            'Something went wrong when running passed function.'
+            "Something went wrong when executing passed callback. #{e.message}"
           )
           stop!
         end

spec/config_manager/async_scheduler_spec.rb

@@ -0,0 +1,37 @@
+# frozen_string_literal: true
+
+#
+#    Copyright 2019, Optimizely and contributors
+#
+#    Licensed under the Apache License, Version 2.0 (the "License");
+#    you may not use this file except in compliance with the License.
+#    You may obtain a copy of the License at
+#
+#        http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS,
+#    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#    See the License for the specific language governing permissions and
+#    limitations under the License.
+#
+require 'spec_helper'
+require 'optimizely/config_manager/async_scheduler'
+require 'optimizely/logger'
+
+describe Optimizely::AsyncScheduler do
+  it 'should log error trace when callback fails to execute' do
+    def some_callback(_args); end
+
+    spy_logger = spy('logger')
+
+    scheduler = Optimizely::AsyncScheduler.new(method(:some_callback), 10, false, spy_logger)
+    scheduler.start!
+
+    while scheduler.running; end
+    expect(spy_logger).to have_received(:log).with(
+      Logger::ERROR,
+      'Something went wrong when executing passed callback. wrong number of arguments (given 0, expected 1)'
+    )
+  end
+end