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no-confusing-non-null-assertion

Disallow non-null assertion in locations that may be confusing.

🎨

Extending "plugin:@typescript-eslint/stylistic" in an ESLint configuration enables this rule.

💡

Some problems reported by this rule are manually fixable by editor suggestions.

Using a non-null assertion (!) next to an assign or equals check (= or == or ===) creates code that is confusing as it looks similar to a not equals check (!= !==).

a! == b; // a non-null assertions(`!`) and an equals test(`==`)
a !== b; // not equals test(`!==`)
a! === b; // a non-null assertions(`!`) and an triple equals test(`===`)

This rule flags confusing ! assertions and suggests either removing them or wrapping the asserted expression in () parenthesis.

.eslintrc.cjs
module.exports = {
  "rules": {
    "@typescript-eslint/no-confusing-non-null-assertion": "error"
  }
};

Try this rule in the playground ↗

Examples​

interface Foo {
  bar?: string;
  num?: number;
}

const foo: Foo = getFoo();
const isEqualsBar = foo.bar! == 'hello';
const isEqualsNum = 1 + foo.num! == 2;
Open in Playground

Options​

This rule is not configurable.

When Not To Use It​

If you don't care about this confusion, then you will not need this rule.

Further Reading​

Resources​