feat(precision): add -p, --precision option

[saunders1989]

We have an issue where we want to bump the coverage but don't want to bump it by 2 decimal places. We want to bump it by a whole number. so if our margin is 1 and the increase is 1.65% we want to go from 40 -> 41 instead of 41.65.

I think this also addresses the issues been spoken about here - #17

Also please feel free to rip this apart and tell me if you'd like changes. it would be great to get this in :)

[rbardini]

Thanks, @saunders1989! Left a couple comments.

Also, please remember to update the README with the new option. You can run jest-it-up --help and copy-paste the output.

[rbardini]

This is great, but I think we could have a more generic solution:

Suggested change

	.option(
	'-w, --whole-number',
	'round coverage thresholds down to whole a whole number',
	)
	.option('-p, --precision <digits>',
	'number of threshold decimal places to persist',
	parseInt,
	2,
	)

You can then do +desiredCoverage.toFixed(precision) in getNewThresholds, and pass --precision 0 if you want whole numbers. What do you think?

[saunders1989]

I like the idea of what you have proposed however i just found out that if the coverage is 30.6, and we want precision 0 it will then round up to 31. technically the coverage isnt at 31 so would fail i think

[rbardini]

Oh right, I forgot toFixed() rounds the number. In that case we would need something like this:

const factor = Math.pow(10, precision)
Math.trunc(desiredCoverage * factor) / factor

It may still round numbers due to floating point arithmetic though (e.g. 4.27 with precision 2 → 4.26), but I think that's acceptable, especially since it's opt-in. Alternatively, we could manipulate the number as a string, but that can get ugly pretty quickly.

[rbardini]

I think we should calculate the rounded/truncated desiredCoverage value before this condition, otherwise we may end up updating the number to the same value.

[saunders1989]

Im not quite following what you mean about calculating the number first. could you just explain in a bit more detail please

[rbardini]

We may need to calculate the final desiredCoverage value (accounting for the truncation) before entering this if block.

Let's say desiredCoverage == 50.25, threshold == 50.2, margin == 0. Assuming we support custom precision, and it's 1 in this case, we actually don't need to update coverage thresholds, because the new value would be the same as the current one: 50.2.

So the math you do below must be done earlier, likely together with tolerance:

const desiredCoverage = Math.trunc((coverage - tolerance) * factor) / factor

In fact, we should probably replace the >= with > as well to avoid a 0 bump, but that can be left to a separate PR.

[saunders1989]

@rbardini Hey thanks for the speedy comments back. I've tried to implement what you've talked about. let me know what you'd like changing :)

[schinery]

Wondering if you'd had a chance to look at this @rbardini since the changes were made?

Would love to have this rounding stuff available in a couple of projects 🙏🏻

[rbardini]

Sorry for the delay, folks! LGTM, but index.js tests are failing 😕

@saunders1989 would you mind having a look, please? Some getNewThresholds assertions there are missing the new precision argument.

[saunders1989]

@rbardini sorry about that. obviously didn't run all the tests locally 🤦. i have fixed and updated them so should be good now.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (e17d4ba) 100.00% compared to head (da2b740) 100.00%.

Additional details and impacted files

@@            Coverage Diff            @@
##            master       #20   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            7         7           
  Lines           69        71    +2     
=========================================
+ Hits            69        71    +2     

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[rbardini]

Awesome, thanks @saunders1989!

[github-actions]

🎉 This PR is included in version 3.1.0 🎉

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