pass ratio to the data_labels_format callback when appropriate

[panthony]

That one is a breaking change.

The data_labels_format callback now takes the ratio alongs with value and index.

The ratio is undefined if the chart is not normalized.

I also passed $$.api as this for the format callback in case it can be useful.

[codecov-io]

Codecov Report

Merging #2694 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #2694      +/-   ##
==========================================
+ Coverage   81.02%   81.03%   +<.01%     
==========================================
  Files          59       59              
  Lines        4633     4634       +1     
==========================================
+ Hits         3754     3755       +1     
  Misses        879      879

Impacted Files	Coverage Δ
src/text.js	98.7% <100%> (+0.01%)	⬆️

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[codecov-io]

Codecov Report

Merging #2694 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #2694      +/-   ##
==========================================
+ Coverage   81.02%   81.03%   +<.01%     
==========================================
  Files          59       59              
  Lines        4633     4634       +1     
==========================================
+ Hits         3754     3755       +1     
  Misses        879      879

Impacted Files	Coverage Δ
src/text.js	98.7% <100%> (+0.01%)	⬆️

---

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Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 4163be5...0b65108. Read the comment docs.

[kt3k]

@panthony Isn't it possible to make this not a breaking change? How about making v have the shape of { value: number, ratio: number } only when stack.normalize == true, or passing ratio as 5th argument?

[panthony]

@kt3k I can pass it as 5th argument but it would mean that we'll have callbacks that takes:

(value, ratio, id)

And others:

(value, id, i, j, ratio)

Passing an object would still be a breaking change

[kt3k]

@panthony

we'll have callbacks that takes:
(value, ratio, id)
And others:
(value, id, i, j, ratio)

Ah, that's bad...

Another option could be introducing new option data_labels_formatter (or something) which takes 5 arguments and keep data_labels_format take 4 arguments, though it looks a little tricky to implement and document...

[kt3k]

Anyway we haven't introduced such explicit breaking changes recently except d3 v5 update, I'm going to talk with @masayuki0812 about the policy and how we update the version number if we do breaking changes.

[panthony]

@kt3k Not sure if always possible but maybe we could pass directly the data point in all callbacks.

This way we have everything (id, index, value, ratio, any other attributes that may be added) and new attributes could be added in the future without API break.

To ease the upgrade we could introduce a boolean in the config to toggle the previous/new behavior.

Config that would eventually be dropped.

[kt3k]

@panthony

This way we have everything (id, index, value, ratio, any other attributes that may be added) and new attributes could be added in the future without API break.

Sounds nice 👍 I prefer to switch to that API in some future.

To ease the upgrade we could introduce a boolean in the config to toggle the previous/new behavior.

That's sounds reasonable. It would make the upgrade flow more graceful.