feat!: enable ts noImplicitReturns

[wemeetagain]

As discussed offline, this feature helps avoid issues like https://github.com/libp2p/js-libp2p-tcp/issues/185

[achingbrain]

Just tried this out locally. Given this function:

function foo (n: number): string | undefined {
  if (n > 10) {
    return 'ok'
  }
}

I get a ts build error:

 error TS7030: Not all code paths return a value.

1   function foo (n: number): string | undefined {

to make the error go away I have to do:

function foo (n: number): string | undefined {
  if (n > 10) {
    return 'ok'
  }

  return undefined   //  <- add this line
}

Do we want this? Seems like it adds unnecessary boilerplate.

If instead we switch @typescript-eslint/explicit-function-return-type to 'error' in eslint-ipfs-config, building succeeds but linting fails, and all we have to do to appease the linter is add the return type, not the extra return undefined.

What do you think?

[achingbrain]

The ts config change in this PR doesn't seem to actually require return types either, only when there's a branch in the function in question that affects the return type.

The eslint rule OTOH is a little less forgiving and requires return types all the time, regardless of the function structure.

By which I mean this builds fine with noImplicitReturns: true but needs "@typescript-eslint/explicit-function-return-type": "error" to fail linting:

function foo () {
  return 'hello'
}

[achingbrain]

See: https://github.com/ipfs/eslint-config-ipfs/pull/114

[BigLep]

Closing in favor of https://github.com/ipfs/eslint-config-ipfs/pull/114, which will get dependency updated in aegir by dependabot.