Event with namespace specified not triggering

[Ciappone]

• Cytoscape.js version : 3.20.0 ( tested with 3.28.1 too )
• Browser/Node.js & version : Google Chrome v. 123.0.6312.122 / Mozilla Firefox v. 124.0.2

Current (buggy) behaviour

If I assign an event ( "select" in this case ) with a namespace specified the event doesn't trigger or the Event object's property "namespace" is null

Desired behaviour

The event should trigger normally and have the Event object's property "namespace" valorized with the one assigned

Minimum steps to reproduce

I tried assigning the event in two ways:

• first: in this case the event doesn't trigger

 cy.on("select.test","node",(evt) => {
    document.getElementById("log").innerHTML += "Node selected with namespace: " + evt.namespace+"<br />";
  });

• second: in this case the event trigger but the namespace is null

 cy.on("select","node",(evt) => {
    document.getElementById("log").innerHTML += "Node selected with namespace: " + evt.namespace+"<br />";
  },'test');

I'll add a JSBin where you can see the problem
JSBin

[mikekucera]

I'm not 100% sure what the utility of the 'namespace' field is, but I don't think the behaviour of the JSBin is wrong.

Both listeners and events can provide a namespace. When the listener specifies a namespace it will only run if the event has the same namespace.

In the sample JSBin the event that fires when selecting a node is just "select", which does not match "select.test", that's why the handler doesn't run. It appears to be intended to work this way.

You can see here, if the listener has a namespace it must match the event's namespace. The "select" event doesn't have a namespace so it doesn't match "select.test":
https://github.com/cytoscape/cytoscape.js/blob/unstable/src/emitter.js#L203

Also, cy.on(...) doesn't take a 4th parameter.
https://js.cytoscape.org/#cy.on

I don't know of any examples of built-in cy.js events that have namespaces. They may exist but I'm not aware of any.

You can manually fire an event with a namespace by calling cy.emit("foo.namespace"), which appears to work as expected.

In other words I don't think this is a bug.

Thank you.