Zeppelin 0.6.2 angular watch

ZeppelinAngularWatch.scala

// 1. Sequence of binding events on angular watch
// 2. nulls are accepted as both initial and new value
// 3. using the same value (even null) twice triggers the watch 
// 4. Multiple watchers on the same variable
// 5. Bug in watch (before, after) 
// 6. Use watch (before, after, context) - it is working as expected
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
val logger: Logger = LoggerFactory.getLogger("MyZeppelinLogger");

z.angularUnwatch("ax4_var")
logger.debug("Before binding");
z.angularBind("ax4_var", null)
logger.debug("After binding. Before watch configured");
z.angularWatch("ax4_var", (before, after, ctx) => {
    logger.debug(s"Watch (before, after, ctx) triggered. Old value=$before New value=$after");
}) 
z.angularWatch("ax4_var", (before, after) => {
    logger.debug(s"Watch (before, after) triggered. Old value=$before New value=$after");
}) 

logger.debug("Watch configured");
// Triggers watch 1?
z.angularBind("ax4_var", null)
// Triggers watch 2?
z.angularBind("ax4_var", null)
// Triggers watch 3?
z.angularBind("ax4_var", "string for a change")
// Triggers watch 4?
z.angularBind("ax4_var", "new string")


// Log results:
// ...
//[DEBUG] 2017-03-15 04:40:10.093 [pool-2-thread-13] MyZeppelinLogger - Before binding 
//[DEBUG] 2017-03-15 04:40:10.361 [pool-2-thread-13] MyZeppelinLogger - After binding. Before watch configured 
//[DEBUG] 2017-03-15 04:40:10.898 [pool-2-thread-13] MyZeppelinLogger - Watch configured 
//[DEBUG] 2017-03-15 04:40:11.035 [pool-24-thread-19] MyZeppelinLogger - Watch (before, after, ctx) triggered. Old value=null New value=null 
//[DEBUG] 2017-03-15 04:40:11.036 [pool-24-thread-10] MyZeppelinLogger - Watch (before, after) triggered. Old value=null New value=null 
//[DEBUG] 2017-03-15 04:40:11.168 [pool-24-thread-20] MyZeppelinLogger - Watch (before, after, ctx) triggered. Old value=null New value=null 
//[DEBUG] 2017-03-15 04:40:11.168 [pool-24-thread-40] MyZeppelinLogger - Watch (before, after) triggered. Old value=null New value=null 
//[DEBUG] 2017-03-15 04:40:11.277 [pool-24-thread-21] MyZeppelinLogger - Watch (before, after, ctx) triggered. Old value=null New value=string for a change 
//[DEBUG] 2017-03-15 04:40:11.278 [pool-24-thread-11] MyZeppelinLogger - Watch (before, after) triggered. Old value=string for a change New value=string for a change 
//[DEBUG] 2017-03-15 04:40:11.381 [pool-24-thread-22] MyZeppelinLogger - Watch (before, after, ctx) triggered. Old value=string for a change New value=new string 
//[DEBUG] 2017-03-15 04:40:11.382 [pool-24-thread-44] MyZeppelinLogger - Watch (before, after) triggered. Old value=new string New value=new string