Fix update prototype sample code

[kennethkalmer]

Sample JS snippet incorrectly shows myLineChart.data being updated instead of myLineChart.config.data.

[etimberg]

I'm not sure this is wrong, changing chart.data should work as well

[kennethkalmer]

@etimberg thanks for the response. I spent 2 hours battling with it thinking I didn't understand how ClojureScript & JavaScript interop worked... Then I had a cursory look at the samples and saw that they mostly use config.data, and suddenly it all worked.

[simonbrunel]

@kennethkalmer do you have an example that show your issue? I tried to update a chart using chart.data and it works fine. chart.data is an alias of config.data, so both should work the same but chart.data is the preferred form. The only difference is that you can't assign a new object to chart.data (e.g. chart.data = { ... }), we still need to define a setter.

Duplicated of #3785

[kennethkalmer]

@simonbrunel Aha! That makes sense, I was blatantly reassigning chart.data with chart.data = {labels: [], datasets: []}. So until the setter is made I recommend the documentation gets modified to indicate this (or even updated regardless for people using the versions prior to the version getting the setter).

I can take a stab at improving it in this way if you'd like?

[simonbrunel]

@kennethkalmer I'm going to implement the setter with unit tests but also try to clean up examples to use chart.data instead of config.data. I can also update the doc with a note about chart.data = {} not working for version prior 2.6 (I don't think we will get the doc re-deployed before then :).

@etimberg thoughts?

[simonbrunel]

@kennethkalmer closing in favor of #3897, let me know your thoughts about that changes.