@typescript-eslint/no-unnecessary-boolean-literal-compare

If a value is a boolean, value === true is the same as value, and value === false is the same as !value. The comparison adds nothing.

A boolean | undefined is allowed by default, because there === true also decides what happens with undefined. A boolean | string is never reported.

--fix replaces the comparison with the value or its negation.

Configure#

Off by default. This rule needs types, so turning it on makes bun lint type check your code first.

bunfig.toml

[lint.rules]
"@typescript-eslint/no-unnecessary-boolean-literal-compare" = "error"

Every option, set to its default:

bunfig.toml

[lint.rules]
"@typescript-eslint/no-unnecessary-boolean-literal-compare" = ["error", {
  allowComparingNullableBooleansToTrue = true,
  allowComparingNullableBooleansToFalse = true,
  allowRuleToRunWithoutStrictNullChecksIKnowWhatIAmDoing = false,
}]

Examples#

example.ts2 problems

function canEdit(isOwner: boolean, isLocked: boolean) {
  return isOwner === true && isLocked === false;
}

example.tsNo problems

function canEdit(isOwner: boolean, isLocked: boolean) {
  return isOwner && !isLocked;
}

function isPinned(pinned?: boolean, mode?: boolean | string) {
  return pinned === true || mode === true;
}

Options#

Option	Default	What it does
`allowComparingNullableBooleansToTrue`	`true`	Allow `value === true` where `value` can also be `null` or `undefined`.
`allowComparingNullableBooleansToFalse`	`true`	Allow `value === false` where `value` can also be `null` or `undefined`.
`allowRuleToRunWithoutStrictNullChecksIKnowWhatIAmDoing`	`false`	Without `strictNullChecks` in `tsconfig.json`, the rule can't tell what can be `null`, and it reports that once for each file. Set this to `true` to turn that report off.

With allowComparingNullableBooleansToTrue off, write if (isPinned) instead:

example.tswith { "allowComparingNullableBooleansToTrue": false }1 problem

function pin(isPinned?: boolean) {
  if (isPinned === true) {
    console.log("pinned");
  }
}

With allowComparingNullableBooleansToFalse off, write !(isPinned ?? true) instead, which says what undefined counts as:

example.tswith { "allowComparingNullableBooleansToFalse": false }1 problem

function pin(isPinned?: boolean) {
  if (isPinned === false) {
    console.log("not pinned");
  }
}