fix(eslint-plugin): [explicit-function-return-type] support AllowTypedFunctionExpression within AllowHigherOrderFunction

[lonyele]

PR Checklist

• Addresses an existing issue:
  Fixes [explicit-function-return-type] Return type needed after injection by higher order functions despite options #758
  Fixes [explicit-function-return-type] allowTypedFunctionExpressions should support return values and default parameters #682
  Fixes [explicit-function-return-type] option to ignore return value on functions with return type signatures #2839
• That issue was marked as accepting prs
• Steps in CONTRIBUTING.md were taken

Overview

Before

It errors when the last return type of higher order function is not typed even though AllowTypedFunctionExpression is true

After

If the ancestor(top level) is typed, ignore the last return type of higher order function since It is explicitly typed at the beginning.

Context

It seems like this functionality has already been used at explicit-boundary-module-type which looks to be usable at this rule finding if the top level is already typed. I wanted to use ancestorHasReturnType somewhere inside of isTypedFunctionExpression or checkFunctionExpressionReturnType , but these are also used at explicit-boundary-module-type liek this thus I made this solution. Hope I got near to the solution.

Big shame that I didn't finish other PR's that you've already commented... I haven't thought about me away from programming for somehow. From now on, I plan to finish some unfinished jobs(#894, #901) and I thought this functionality needs to be done first

[typescript-eslint]

Thanks for the PR, @lonyele!

typescript-eslint is a 100% community driven project, and we are incredibly grateful that you are contributing to that community.

The core maintainers work on this in their personal time, so please understand that it may not be possible for them to review your work immediately.

Thanks again!

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✅ Successfully ran 44 targets

• Node 12.x - nx run-many --target=typecheck --all --parallel
• Node 12.x - nx run-many --target=build --all --parallel --exclude website --exclude website
• Node 16.x - nx test @typescript-eslint/eslint-plugin-tslint
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• Node 16.x - nx test @typescript-eslint/parser
• Node 16.x - nx test @typescript-eslint/experimental-utils
• Node 16.x - nx test @typescript-eslint/scope-manager
• Node 16.x - nx test @typescript-eslint/visitor-keys
• Node 14.x - nx test @typescript-eslint/eslint-plugin-tslint
• Node 14.x - nx test @typescript-eslint/eslint-plugin
• Node 16.x - nx test @typescript-eslint/typescript-estree
• Node 14.x - nx test @typescript-eslint/parser
• Node 12.x - nx test @typescript-eslint/eslint-plugin-tslint
• Node 16.x - nx run-many --target=build --all --parallel --exclude website --exclude website
• Node 14.x - nx test @typescript-eslint/experimental-utils
• Node 12.x - nx test @typescript-eslint/eslint-plugin
• Node 14.x - nx test @typescript-eslint/scope-manager
• Node 12.x - nx test @typescript-eslint/parser
• Node 14.x - nx test @typescript-eslint/visitor-keys
• Node 12.x - nx test @typescript-eslint/experimental-utils
• Node 12.x - nx run-many --target=build --all --parallel --exclude website --exclude website
• Node 14.x - nx test @typescript-eslint/typescript-estree
• Node 12.x - nx test @typescript-eslint/scope-manager
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• Node 12.x - nx test @typescript-eslint/visitor-keys
• Node 16.x - nx prebuild @typescript-eslint/types
• Node 12.x - nx test @typescript-eslint/eslint-plugin-internal
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• Node 12.x - nx prebuild @typescript-eslint/types
• Node 12.x - nx prebuild @typescript-eslint/types

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[codecov]

Codecov Report

Merging #4250 (10922cd) into main (bade083) will increase coverage by 0.32%.
The diff coverage is 88.00%.

❗ Current head 10922cd differs from pull request most recent head a7365e0. Consider uploading reports for the commit a7365e0 to get more accurate results

@@            Coverage Diff             @@
##             main    #4250      +/-   ##
==========================================
+ Coverage   93.88%   94.20%   +0.32%     
==========================================
  Files         297      152     -145     
  Lines       11179     8111    -3068     
  Branches     3246     2595     -651     
==========================================
- Hits        10495     7641    -2854     
+ Misses        416      266     -150     
+ Partials      268      204      -64     

Flag	Coverage Δ
unittest	94.20% <88.00%> (+0.32%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...plugin/src/rules/explicit-module-boundary-types.ts	91.04% <ø> (+0.97%)	⬆️
.../eslint-plugin/src/util/explicitReturnTypeUtils.ts	96.42% <84.21%> (-3.58%)	⬇️
...-plugin/src/rules/explicit-function-return-type.ts	100.00% <100.00%> (ø)
packages/scope-manager/src/lib/es6.ts
...ages/scope-manager/src/lib/esnext.asynciterable.ts
packages/scope-manager/src/lib/es2015.symbol.ts
packages/scope-manager/src/scope/BlockScope.ts
packages/scope-manager/src/lib/esnext.weakref.ts
...ackages/scope-manager/src/referencer/Referencer.ts
...ges/scope-manager/src/lib/es2018.asyncgenerator.ts
... and 138 more

[JoshuaKGoldberg]

Looks good to me, thanks!

I'm a little shaky on this rule in particular so I'll defer to another maintainer on full approval.

[JoshuaKGoldberg]

assume... what?

[bradzacher]

this was copy pasted from the old code.
idk what it was supposed to be (I probably wrote it lol)

[lonyele]

I think it was just a mistake to remove it. Comments on this function I found are already giving some good "whys" and leaving it may confuse others(actually including me when I first saw it :D) thus I removed it.

[bradzacher]

I see you've added tests for

          allowTypedFunctionExpressions: true,
          allowHigherOrderFunctions: true,

Could you also ensure that there are suitable tests for all of these option combos as well?

          allowTypedFunctionExpressions: false,
          allowHigherOrderFunctions: true,

          allowTypedFunctionExpressions: true,
          allowHigherOrderFunctions: false,

          allowTypedFunctionExpressions: false,
          allowHigherOrderFunctions: false,

Just want to ensure that there aren't any regressions accidentally introduced by a change in logic in this very complicated rule!

[lonyele]

Yeah, you were dead right. There was a flaw. I somehow touched this same code before when figuring out how to approach this problem and missed including it in my final approach. Now it looks much better.

[bradzacher]

thanks for building this!