infra(typescript-eslint): switch-exhaustiveness-check

[ST-DDT]

Ref: #2508

• infra(unicorn): no-useless-switch-case #2508

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Enables the @typescript-eslint/switch-exhaustiveness-check lint rule.

This removes default cases that are already covered by the explicit case statements on union types. Delayed to v9.

There are some non-union type switch cases that aren't exhaustive, and won't be detected by typescript-eslint.
I will create a separate issue for that on typescript-eslint's side.

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Related Issues and PRs:

• feat(eslint-plugin): [switch-exhaustiveness-check] add an option to warn against a default case on an already exhaustive switch typescript-eslint/typescript-eslint#7539
• [switch-exhaustiveness-check] Require default case if discriminant type is not a union typescript-eslint/typescript-eslint#2959

[codecov]

Codecov Report

Merging #2519 (4e600b8) into next (6f977f6) will decrease coverage by 0.01%.
The diff coverage is 100.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##             next    #2519      +/-   ##
==========================================
- Coverage   99.57%   99.57%   -0.01%     
==========================================
  Files        2787     2787              
  Lines      249373   249376       +3     
  Branches     1079     1080       +1     
==========================================
+ Hits       248316   248318       +2     
- Misses       1029     1030       +1     
  Partials       28       28              

Files	Coverage Δ
src/modules/color/index.ts	99.79% <100.00%> (+<0.01%)	⬆️

... and 2 files with indirect coverage changes

[matthewmayer]

Doesn't this change the behavior when called from JavaScript?

[ST-DDT]

Yes, it does. Should we delay the default removal to v9? (Although I consider those bad arguments unsupported usage anyway)

[matthewmayer]

i support including this in v9.

[matthewmayer]

Looks good without the breaking changes

[ST-DDT]

@matthewmayer I reverted the breaking changes for now, so we can enable this rule.
I will create a new PR once the additional options have been added to the rule by typescript-eslint.

[ST-DDT]

Created typescript-eslint PR: typescript-eslint/typescript-eslint#7880

• feat(eslint-plugin): [switch-exhaustiveness-check] add requireDefaultForNonUnion option typescript-eslint/typescript-eslint#7880