no-collection-size-mischeck.md

no-collection-size-mischeck

🔧 fixable

The size of a collection and the length of an array are always greater than or equal to zero. So testing that a size or length is greater than or equal to zero doesn't make sense, since the result is always true. Similarly testing that it is less than zero will always return false. Perhaps the intent was to check the non-emptiness of the collection or array instead.

Noncompliant Code Example

if (someSet.size >= 0) { // Noncompliant
  //...
}

if (someMap.size < 0) { // Noncompliant
  //...
}

const result = someArray.length >= 0; // Noncompliant

Compliant Solution

if (someSet.size > 0) {
  //...
}

if (someMap.size == 0) {
  //...
}

const result = someArray.length > 0;

Note

The rule behaves differently depending on which parser is used. With the default parser, the rule performs syntactic analysis and considers only the property of the target object. With typescript-eslint/parser, and if correctly configured, the rule relies on type information and checks also that the target object is indeed a collection to avoid false-positives.