Add diff-sequences package

[pedrottimark]

This generic package has specific goals for jest-diff in a future pull request:

• Minimize time and space when expected and received values have many differences.
• Minimize code differences between --expand and --no-expand options.

Here are recommended steps to review this pull request:

1. Read README.md especially the examples of callback functions

2. Refer to An O(ND) Difference Algorithm and Its Variations by Eugene W. Myers

   • Read up through Figure 1 on page 3 and make sure to understand the “edit graph” analogy
   • Read pseudo code in Figure 2 on page 6
   • Look at Figure 3 Furthest reaching paths on page 7
   • Read pseudo code on pages 11 and 12

3. Read tests in index.test.js

4. The first time you read code in index.js skip the two Overlappable functions

Overview of cost:

• time and space optimization: skip diagonals in which paths cannot ever overlap

• heap used is two arrays of small integers: each has max length of one more than length of shorter sequence

• stack depth is at most logarithm of number of differences [EDIT optimization: does not recurse whenever number of changes is equal to number of items in either half of divided interval, therefore cannot contain any common items]

Test plan

44 tests [EDIT: plus 4 and forgot to say 100% coverage]

[codecov-io]

Codecov Report

Merging #5407 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #5407   +/-   ##
=======================================
  Coverage   61.35%   61.35%           
=======================================
  Files         205      205           
  Lines        6925     6925           
  Branches        4        3    -1     
=======================================
  Hits         4249     4249           
  Misses       2675     2675           
  Partials        1        1

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[pedrottimark]

Residue:

• [EDIT: Caleb gave me the correct solution to type cast intention invalid arg as any] Flow reports This type is incompatible with the expected param type of for 3 of the invalid arg tests. I used // $FlowFixMe comment preceding the call, but would like to replace it with more specific // flowlint-line TODO:off if I can find what is the name of that error.

• When I tried module.exports = diffSequences; following the example of 3 packages which have browser builds, ESLint reported No default export found maybe because index.js does not import anything?

[pedrottimark]

[EDIT: No need to export types of input and output callback functions, because type of default export includes its args, true?] Thinking ahead to when jest-diff replaces its diff dependency with this package, should I move the exported types IsCommon and FoundSubsequence for callback functions to a file in the types folder? And define a type like FindSubsequences for the default export?

For other projects to type check this package as a dependency means that it will need definitions in flow-typed and definitely-typed?

[cpojer]

This is a huge diff but it looks really really good.

• Can you use ES exports instead?
• Flow-typed makes sense if you wanna use it outside of this repo.

[github-actions]

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