.off(): unexpected behavior

[johnd0e]

.off() method unexpectedly removes listeners of the parent object

• I've looked at the documentation to make sure the behavior is documented and expected
• I'm sure this is a Leaflet code issue, not an issue with my own code nor with the framework I'm using (Cordova, Ionic, Angular, React…)
• I've searched through the issues to make sure it's not yet reported

Steps to reproduce
Steps to reproduce the behavior:

• create any layer and add it Layers control
• attach on 'overlayadd' event listener to map
• remove listeners from layer (https://leafletjs.com/reference-1.4.0.html#layergroup-off)

Expected behavior

Only listeners directly attached to layer should be removed

Current behavior

map listeners get removed too, unexpectedly

Environment

• Leaflet version: 1.4
• Browser (with version): Chrome 73.0.3683.103 (Official Build) (32-bit)
• OS/Platform (with version): Windows 10 (32-bit)

Additional context

It can appear that this behavior is by current leaflet design.
In this case we should at least document it explicitly and in detail!

Minimal example reproducing the issue

var map = mymap;
var layer = L.layerGroup();
L.control.layers({},{layer:layer}).addTo(map);

map.on('overlayadd',()=>map.openTooltip('map event',map.getCenter()));

// uncomment this to see the issue:

//layer.off()

https://jsfiddle.net/johnd0e/jy84gsL2/16/

[johnd0e]

Current behavior is highly undesirable in my setup, because:

• map listeners is bound in main script
• layer(s) is processed in independent plugin(s)

So I'd prefer if plugin'd not affect main script base functionality.

[IvanSanchez]

Expected behavior

Only listeners directly attached to layer should be removed

I disagree. The point of .off()is to remove all event listeners, no matter where they were attached from.

In this case we should at least document it explicitly and in detail!

I agree with this. This should be a simple case of changing the wording at...

Leaflet/src/core/Events.js

Line 68 in 3f5979b

* Removes all listeners to all events on the object.

...and adding something like "This includes implicitly attached events". Not sure what the best wording would be.

[johnd0e]

The point of .off()is to remove all event listeners, no matter where they were attached from.

I can agree with this.
But then it would be convenient to have also more 'safe' version of .off, which unbind only explicit listeners.

[IvanSanchez]

But there is no way to tell apart "implicit" versus "explicit" event listeners in the code.

[johnd0e]

Well, I suppose we can improve the code. Like, add owner to every listener as a property.