babel-plugin-typescript-non-null-assertion-runtime

Summary

TypeScript has non-null-assertion to assert some expression is not nullable.
But it's a type only feature. Which means nothing will happend if the non-nullable value is nullable. It's a little hard to call it an assertion.

This plugin will adds runtime assert into all TypeScript non-null-assertion. And also we can add some additional easily.

With runtime assertion, we may find bugs as early as possible.

Install

1. Run yarn add babel-plugin-typescript-non-null-assertion-runtime --dev
2. Setup your babel config file. You can see using-a-plugin

Example

If we have below code:

const a = {
    b: 1,
};

a!.b = 1;
a.b! = 2;
const c = a!.b;
const d = a.b!;

And it will transform to:

function _nonNull(expr, message = "NonNull assertion failed") {
  if (expr === undefined || expr === null) {
    throw new Error(message);
  }

  return expr;
}

const a = {
  b: 1,
};
_nonNull(a).b = 1;
a.b! = 2;

const c = _nonNull(a).b;

const d = _nonNull(a.b);

Options

• assertFunctionName: optional, name of assert function.
• assertMessage: optional, error message of assert.
• errorMessageIncludeSource: optional, include assert expression into error message.