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no-non-null-asserted-nullish-coalescing

Disallow non-null assertions in the left operand of a nullish coalescing operator.

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

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

The ?? nullish coalescing runtime operator allows providing a default value when dealing with null or undefined. Using a ! non-null assertion type operator in the left operand of a nullish coalescing operator is redundant, and likely a sign of programmer error or confusion over the two operators.

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

Try this rule in the playground ↗

Examples​

foo! ?? bar;
foo.bazz! ?? bar;
foo!.bazz! ?? bar;
foo()! ?? bar;

let x!: string;
x! ?? '';

let x: string;
x = foo();
x! ?? '';
Open in Playground

Options​

This rule is not configurable.

When Not To Use It​

If your project's types don't yet fully describe whether certain values may be nullable, such as if you're transitioning to strictNullChecks, this rule might create many false reports. You might consider using ESLint disable comments for those specific situations instead of completely disabling this rule.

Further Reading​

Resources​