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/strict-boolean-expressions/

Description

Hello! We believe strongly that strict boolean expressions are a good thing, because truthy evaluation opens the door for developer error and bugs to slip into the wild.

For this reason, we very much like the power of the strict-boolean-expressions rule.

The challenge we are facing, is how auto-fix conflicts with some other rules that we believe are very valuable:

1. eqeqeq - We agree with the philosophy of the rule: It is considered good practice to use the type-safe equality operators === and !== instead of their regular counterparts == and !=. The reason for this is that == and != do type coercion.
2. no-eq-null - Comparing to null without a type-checking operator (== or !=), can have unintended results as the comparison will evaluate to true when comparing to not just a null, but also an undefined value.

The fixes and suggestions (specifically the auto-fix for objects when allowNullableObject is false) conflict with the above rules.

I am sure that there is good reason and a lot of discussion behind why there was a decision to use == null as opposed to === undefined, but I thought it would be worth opening a discussion to see if we can get a consensus that it would be preferable to change the behavior to align more with the core eslint rules and the philosophy behind why it is a good idea to enable them.

Fail

let obj;
if (Math.random() > 0.5) {
  obj = {};
}

if (obj) {
  console.log('I am set!');
}

Pass

// Current behavior
let obj;
if (Math.random() > 0.5) {
  obj = {};
}

if (obj != null) {
  console.log('I am set!');
}

// Preferred behavior
let obj;
if (Math.random() > 0.5) {
  obj = {};
}

if (obj !== undefined) {
  console.log('I am set!');
}

Additional Info

• There are a couple issues I found with some information on the topic, but it is not explicit about this particular choice so I thought it was worth opening a new thread:

  • [strict-boolean-expressions] False positive when using union types #2894
  • Docs: [strict-boolean-expressions] nullable number as wrong 'undefined' type #5587