fix: adjust domain & range for single value histogram

[emmacunningham]

Summary

fix #262

Previously, a line annotation within a single value histogram's domain range would not appear correctly, rendering the line at the domain start position. For example with a single value histogram with domain 3 to 4, an annotation line at 3.5 would be rendered at 3. This PR adds handling for computing the x scale for a single value histogram such that the line now correctly renders in the right position:

The issue was that the annotations rely on the xScale for the x-axis position but with a single value domain, calling xScale.scale would return 0 for all values because the domain and range passed into the scale constructor created a scale that could not compute the right values because the domain would be single value ([3, 3] for our example) and the range would also be single value ([0, 0] in the example here).

To address this, we now do a check in computeXScale such that if the enableHistogramMode flag is true and the domain is a single value domain, we adjust the domain and range values passed into the constructor so that the returned scale's domain and range have been adjusted to account for histogram mode (the domain is extended by the minInterval, which will default to 1 unless the user passes in a custom minInterval for xDomain).

Checklist

Use strikethroughs to remove checklist items you don't feel are applicable to this PR.

- [ ] Any consumer-facing exports were added to src/index.ts (and stories only import from ../src except for test data & storybook)

• 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
• Each commit follows the convention

[codecov-io]

Codecov Report

Merging #265 into master will increase coverage by 0.07%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #265      +/-   ##
==========================================
+ Coverage   98.12%   98.19%   +0.07%     
==========================================
  Files          36       37       +1     
  Lines        2662     3319     +657     
  Branches      607      821     +214     
==========================================
+ Hits         2612     3259     +647     
- Misses         45       50       +5     
- Partials        5       10       +5

Impacted Files	Coverage Δ
src/state/chart_state.ts	97.95% <ø> (+0.5%)	⬆️
src/state/utils.ts	97.03% <100%> (+0.43%)	⬆️
src/lib/axes/axis_utils.ts	100% <100%> (ø)	⬆️
src/lib/series/scales.ts	100% <100%> (ø)	⬆️
src/state/crosshair_utils.ts	90.8% <0%> (-0.87%)	⬇️
src/lib/series/rendering.ts	98.45% <0%> (-0.83%)	⬇️
src/lib/utils/scales/scale_continuous.ts	93.38% <0%> (-0.73%)	⬇️
src/lib/series/specs.ts	100% <0%> (ø)	⬆️
src/state/annotation_utils.ts	100% <0%> (ø)	⬆️
src/lib/series/series.ts	100% <0%> (ø)	⬆️
... and 11 more

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[markov00]

Code LGTM just added a minor comment. Tested locally.

[markov00]

LGTM!

[markov00]

🎉 This PR is included in version 8.0.2 🎉

The release is available on:

• GitHub release
• npm package (@latest dist-tag)

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