typescript/no-non-null-assertion Restriction

What it does

Disallow non-null assertions using the ! postfix operator.

Why is this bad?

TypeScript's ! non-null assertion operator asserts to the type system that an expression is non-nullable, as in not null or undefined. Using assertions to tell the type system new information is often a sign that code is not fully type-safe. It's generally better to structure program logic so that TypeScript understands when values may be nullable.

Examples

Examples of incorrect code for this rule:

x!;
x!.y;
x.y!;

Examples of correct code for this rule:

x;
x?.y;
x.y;

How to use

To enable this rule using the config file or in the CLI, you can use:

Config (.oxlintrc.json)

{
  "rules": {
    "typescript/no-non-null-assertion": "error"
  }
}

CLI

oxlint --deny typescript/no-non-null-assertion

References

• Rule Source