Before You File a Proposal Please Confirm You Have Done The Following...

• I have searched for related issues and found none that match my proposal.
• I have searched the current rule list and found no rules that match my proposal.
• I have read the FAQ and my problem is not listed.

My proposal is suitable for this project

• I believe my proposal would be useful to the broader TypeScript community (meaning it is not a niche proposal).

Link to the rule's documentation

https://typescript-eslint.io/rules/switch-exhaustiveness-check/

Description

I propose that the switch-exhaustiveness-check checks switch statements that operate on non-union-types and require them to have a default case to ensure they are exhaustive.

Fail

const value: number = Math.floor(Math.random() * 3);
switch (value) {
  case 0:
    console.log("zero");
    return;
  case 1:
    console.log("one");
    return;
}

Pass

const value: number = Math.floor(Math.random() * 3);
switch (value) {
  case 0:
    console.log("zero");
    return;
  case 1:
    console.log("one");
    return;
  default:
    console.log("higher");
    return;
  // Or
  default:
    // Do nothing
}

Additional Info

Since it would break projects that have the switch-exhaustiveness-check enabled, but don't have all their switch statements fully exhaustive, this should probably locked behind a default false option. Maybe this could be turned on by default with the next major version.

This option can not be replaced with default-case due to #7539.

• feat(eslint-plugin): [switch-exhaustiveness-check] add an option to warn against a default case on an already exhaustive switch #7539

Originally searched for during:

• infra(typescript-eslint): switch-exhaustiveness-check faker-js/faker#2519