// SPDX-FileCopyrightText: Copyright Orangebot, Inc. and Medplum contributors
// SPDX-License-Identifier: Apache-2.0
// Helper that tests a condition that we believe should always be true.
//
// This allows programmers to make an assertion to the type system that
// TypeScript can't natively infer. It will throw a runtime error if the
// assertion is ever violated.
//
// Example: After applying a filter to a query that requires the existence of a
// field, you can use invariant to tell TS that the object must have that
// attribute.
//
// ```
// const user = systemRepo.searchOne<User>({
// resourceType: 'User',
// filters: [{ code: 'email', operator: Operator.EQUALS, value: 'alice@example.com' }]
// });
//
// invariant(user.email); // refines user.email from `string | undefined` to `string`
// const result: string = user.email.toLowerCase()
// ```
export function invariant(condition: unknown, msg?: string): asserts condition {
if (!condition) {
throw new Error(msg ?? 'Invariant violation');
}
}
