noExtraNonNullAssertion

Diagnostic Category: lint/suspicious/noExtraNonNullAssertion

TypeScript and TSX

Since: v1.0.0

Sources:

Same as: @typescript-eslint/no-extra-non-null-assertion

Prevents the wrong usage of the non-null assertion operator (!) in TypeScript files.

The ! non-null assertion operator in TypeScript is used to assert that a value’s type does not include null or undefined. Using the operator any more than once on a single value does nothing.

Examples

Invalid

const bar = foo!!.bar;

code-block.ts:1:13 lint/suspicious/noExtraNonNullAssertion  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ Forbidden extra non-null assertion.
  
  > 1 │ const bar = foo!!.bar;
      │             ^^^^
    2 │ 
  
  ℹ Safe fix: Remove extra non-null assertion.
  
    1 │ const·bar·=·foo!!.bar;
      │                -

function fn(bar?: { n: number }) {
  return bar!?.n;
}

code-block.ts:2:10 lint/suspicious/noExtraNonNullAssertion  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ Forbidden extra non-null assertion.
  
    1 │ function fn(bar?: { n: number }) {
  > 2 │   return bar!?.n;
      │          ^^^^
    3 │ }
    4 │ 
  
  ℹ Safe fix: Remove extra non-null assertion.
  
    2 │ ··return·bar!?.n;
      │             -

function fn(bar?: { n: number }) {
  return ((bar!))?.();
}

code-block.ts:2:12 lint/suspicious/noExtraNonNullAssertion  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ Forbidden extra non-null assertion.
  
    1 │ function fn(bar?: { n: number }) {
  > 2 │   return ((bar!))?.();
      │            ^^^^
    3 │ }
    4 │ 
  
  ℹ Safe fix: Remove extra non-null assertion.
  
    2 │ ··return·((bar!))?.();
      │               -

Valid

const bar = foo!.bar;

obj?.string!.trim();

function fn(key: string | null) {
  const obj = {};
  return obj?.[key!];
}

noExtraNonNullAssertion

Examples

Invalid

Valid

Related links