debug assert

debug-assert.d.ts

export function debugAssert(condition: any, message?: string | (() => string)): asserts condition;

debug-assert.js

const isProduction = process.env.NODE_ENV === "production";
const prefix = "Assertion failed";

function _debugAssert(condition, message) {
  if (isProduction) {
    return;
  }

  if (condition) {
    return;
  }

  const provided = typeof message === "function" ? message() : message;
  const value = provided ? `${prefix}: ${provided}` : prefix;
  throw new Error(value);
}

/** @type {import("./debug-assert.d.ts").debugAssert} */
export const debugAssert = isProduction ? () => {} : _debugAssert;

debug-assert.test.js

import { beforeEach, describe, it } from "node:test";
import assert from "node:assert/strict";
import { debugAssert } from "./debug-assert.js";

describe("debugAssert", () => {
  beforeEach(() => {
    assert(process.env.NODE_ENV !== "production");
  });

  // it("should not throw in production mode", async () => {
  //   const originalEnv = process.env.NODE_ENV;
  //   process.env.NODE_ENV = "production";
  //   // @ts-expect-error we must refresh import
  //   const { debugAssert } = await import("./debug-assert.js?e=prod");
  //   assert.doesNotThrow(() => debugAssert(false));
  //   process.env.NODE_ENV = originalEnv;
  // });

  it("should not throw when condition is truthy", () => {
    assert.doesNotThrow(() => debugAssert(typeof "str" === "string"));
  });

  it("should throw an error when condition is falsy", () => {
    assert.throws(() => debugAssert(false, "Test message"), {
      name: "Error",
      message: "Assertion failed: Test message",
    });
  });

  it("should throw an error with default message if none provided", () => {
    assert.throws(() => debugAssert(false), {
      message: "Assertion failed",
    });
  });

  it("should evaluate message function when provided as a function", () => {
    const messageFunction = () => "Function message";
    assert.throws(() => debugAssert(false, messageFunction()), {
      message: "Assertion failed: Function message",
    });
  });
});