fix(domain): set domain bounds dependent on negative/positive values

[emmacunningham]

Summary

close #135

This PR addresses the issues with the previous scaleToExtent logic assuming a domain with only positive values. Now, when scaleToExtent is false, we return a domain dependent on whether the domain has positive or negative values. Previously, a chart with only negative values would only see the values rendering if scaleToExtent was true; now even when scaleToExtent is false, the negative values will render. For mixed negative & positive values, we return the original domain.

Checklist

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• This was checked for cross-browser compatibility, including a check against IE11
• Proper documentation or storybook story was added for features that require explanation or tutorials
• Unit tests were updated or added to match the most common scenarios
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[codecov-io]

Codecov Report

Merging #149 into master will increase coverage by 0.03%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #149      +/-   ##
==========================================
+ Coverage   94.03%   94.06%   +0.03%     
==========================================
  Files          34       34              
  Lines        1744     1753       +9     
  Branches      219      223       +4     
==========================================
+ Hits         1640     1649       +9     
  Misses         90       90              
  Partials       14       14

Impacted Files	Coverage Δ
src/lib/utils/domain.ts	100% <100%> (ø)	⬆️

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[emmacunningham]

d3.extent() has the type signature [number, number] | [undefined, undefined], so there's a possibility that the computed range start and end could be undefined, though consumers of this function appear to operate under the assumption that this is always [number, number].

This seems like a case where if any value within the computed extent is undefined, we should handle it as an error and surface it to the user somehow (see #117). The other option is that we coerce the undefineds:

[ -start, undefined ] => [ -start, 0 ]
[ +start, undefined ] => [ 0, start ] ?
[ undefined, -end ] => [ end, 0 ] ?
[ undefined, +end ] => [ 0, end ]
[ undefined, undefined ] => [0, 0]

[markov00]

I agree

[markov00]

Code LGTM!

[markov00]

🎉 This PR is included in version 3.7.1 🎉

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