[jest-each]: Add support for keyPaths in test titles

[mattphillips]

Summary

Closes #6452

Opening this up for review early as I want @SimenB @thymikee @rickhanlonii opinion on how to share the getPath logic that is defined in expect.

Add support for $key.path syntax in tagged template test titles.

Example:

// Actions
const increment = () => ({type: 'increment'});
const decrement = () => ({type: 'decrement'});

// Reducer
const reducer = (state = 0, {type}) => {
  switch (type) {
    case 'increment':
      return state + 1;
    case 'decrement':
      return state - 1;
    default:
      return state;
  }
};

test.each`
  state | action         | nextState
  ${0}  | ${increment()} | ${1}
  ${0}  | ${decrement()} | ${-1}
`(
  'returns $nextState when the state is $state and $action.type is dispatched $nextState',
  ({state, action, nextState}) => {
    expect(reducer(state, action)).toEqual(nextState);
  },
);

Test plan

See unit tests

TODO:

• Changelog
• Update docs
• Some how share the getPath logic with expect

[mattphillips]

I've inlined this for now to get it working, it shouldn't stay here :)

[SimenB]

can we just use lodash.get or something?

[mattphillips]

I didn't think we were using lodash anywhere? This getPath algorithm is used in the toHaveProperty matcher and offers a nicer returned value than lodash as it tracks the last visited object.

EDIT: see expect utils

[SimenB]

sticking it in jest-utils should be fine for sharing (although @cpojer hates the util package :D)

[mattphillips]

Should I move it as part of this PR or would it be better in a separate PR?

[SimenB]

As part of this is fine

[mattphillips]

@SimenB have you seen an eslint error like this before?

https://circleci.com/gh/facebook/jest/25790?utm_campaign=vcs-integration-link&utm_medium=referral&utm_source=github-build-link

Not sure what is going wrong 😕

[SimenB]

Syntax error in the browserbuild, which must be es5

[mattphillips]

Hmm @SimenB so it looks like expect cannot depend on jest-util then? How else can we share the getPath code?

[codecov-io]

Codecov Report

Merging #6457 into master will increase coverage by 0.05%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #6457      +/-   ##
==========================================
+ Coverage   63.48%   63.53%   +0.05%     
==========================================
  Files         227      227              
  Lines        8697     8709      +12     
  Branches        4        3       -1     
==========================================
+ Hits         5521     5533      +12     
  Misses       3175     3175              
  Partials        1        1

Impacted Files	Coverage Δ
packages/jest-each/src/bind.js	100% <100%> (ø)	⬆️

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[mattphillips]

@SimenB I've updated this to inline a much simpler getPath function so no need to add anything to jest-util

[SimenB]

remove /files

[github-actions]

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