ignore-rhs should be configurable to only apply outside of conditionals

[lukewlms]

Feature request

We'd like to use ignore-rhs but do not want to use it inside conditionals or other contexts (like the result of a filter() function) which require a boolean. This could potentially be called ignore-rhs-when-bool-not-required though that's wordy.

Here's an example. I'd like the first two statements to get flagged but the third to not be flagged - so in places where we absolutely must have a boolean, we're sure to get a strict one and not, for example, a truthy empty string.

const func = (b: boolean, s: string): boolean | string => {
  // Gets flagged with ignore-rhs on - correct
  if (s) {
    // ...
  }

  // Does not get flagged with ignore-rhs on, but I'd like it to!  We don't want strings inside of if/while/ternaries/filter or anywhere a bool is required
  if (b || s) {
    // ...
  }

  // This does not get flagged and that's good!  Function is able to return a boolean or a string
  return b || s;
}

[tadhgmister]

I don't see where the confusion comes in, typescript has no problems if you add an intermediate variable:

const func = (b: boolean, s: string) => {
    // typescript knows `typeof thing === true | string` according to how || evaluates.
    const thing = b || s;
    // since true | string is not a valid boolean type this gets flagged.
    if(thing){
        // ...
    }
    // however this, even though it evaluates to true | string it is not flagged when passed to an if statement.
    if(b || s){
        // ...
    }
  }

can't the rule do the same? If the expression passed to if/while/ternary is not a boolean then throw an error, I don't even see how ignoring the right hand side would even cause it to ignore that.

[JoshuaKGoldberg]

Yeah, this seems reasonable as a rule option. We could take it in.

Please keep #4534 in mind: we're nearing the deadline for no more non-essential PRs.

[JoshuaKGoldberg]

☠️ TSLint's time has come! ☠️

TSLint is no longer accepting most feature requests per #4534. See typescript-eslint.io for the new, shiny way to lint your TypeScript code with ESLint. ✨

It was a pleasure open sourcing with you all!

[JoshuaKGoldberg]

🤖 Beep boop! 👉 TSLint is deprecated 👈 (#4534) and you should switch to typescript-eslint! 🤖

🔒 This issue is being locked to prevent further unnecessary discussions. Thank you! 👋