Chart.js 3.0.0-rc.5: Plugins are not registered correctly if used for specific chart instances.

[santam85]

Expected Behavior

I expect to be able to specify a plugin for a specific chart instance without having to register it globally

Current Behavior

Plugin is not effective. Not all plugin lifecycle events seem to be called when adding a plugin to a specific chart instance.

Steps to Reproduce

https://codepen.io/santa-85/pen/BaQgqYe?editors=1111
To see correct behaviour, add chartjsPluginAnnotation to the Chart.register call

Environment

• Chart.js version: 3.0.0-rc.5
• Link to your project: Upgrade to Chart.js 3.0 valor-software/ng2-charts#1276

[etimberg]

@santam85 did this happen in other beta/RC versions?

[santam85]

@etimberg I started testing this only since the first rc version, but I suspect it was there for a while.

[kurkle]

The afterRegister / afterUnregister hooks are not called (obviously) on instance plugin. Annotation plugin registers its elements in those hooks, so you'd need to do that manually for it to work.

The elements are not actually exported in that plugin, so this is an oversight there.

Edit: registering the elements is not enough to get the annotation working.
Edit2: descriptors is the 2nd thing needed: https://codepen.io/kurkle/pen/xxgVZgE

[santam85]

The afterRegister / afterUnregister hooks are not called (obviously) on instance plugin

It was not that obvious to me. I would have expected the plugin to be registered when that particular instance of the chart is rendered...

@kurkle how do you suggest I proceed with this? It is not clear to me from the documentation of either the plugin or chart.js itself that if a plugin is used only on an instance, there's a chance it would not work, depending on its implementation. At this point I am even asking myself what's the point of adding a plugin only to an instance, if I need to register all the elements and defaults globally anyway.

[etimberg]

I added some more documentation on the plugin hooks and added some flow charts on how create/update work. There are other hooks (start/stop) that get called for all plugins on a per-chart basis when a plugin is added/removed from the chart instance.

This specific issue with the annotation plugin is because it was never written to handle being applied inline. Depending on the plugin, and what is needs to do, inline can make sense. For example, a plugin to draw the framerate of the chart animations could likely be done with no options, defaults, or registered elements so adding inline is totally fine.

[kurkle]

At this point I am even asking myself what's the point of adding a plugin only to an instance, if I need to register all the elements and defaults globally anyway.

That might be the reason annotation is not designed to work inline. It would anyway need to register its elements and defaults globally, so its no different than disabling it by default.