power-assert make `assert()` of assert module silent

[azu]

I've created reproduce repository.

• https://github.com/azu/issue-power-assert-with-assert

Application code use assert module of Node Core.

index.js

// application code use `assert` module
const assert = require("assert");
export function hello(name) {
    assert(typeof name === "string");
    return "Hello " + name;
}

Test code:

const assert = require("power-assert");
import {hello} from "../src/index";
describe("hello", function () {
    it("should accept string", function () {
        hello(42);  // Should throw error via assert and fail tests.
    });
});

These code are transformed by babel + babel-plugin-espower.

.babelrc

{
  "presets": [
    "es2015"
  ],
  "env": {
    "development": {
      "plugins": [
        "babel-plugin-espower"
      ]
    }
  }
}

When I do this:

npm test

Expected

Fail test

Actual

Pass test :(

---

Reason

Application code is transformed to

"use strict";

Object.defineProperty(exports, "__esModule", {
    value: true
});

var _typeof = typeof Symbol === "function" && typeof Symbol.iterator === "symbol" ? function (obj) { return typeof obj; } : function (obj) { return obj && typeof Symbol === "function" && obj.constructor === Symbol ? "symbol" : typeof obj; };

var _powerAssertRecorder = function () { function PowerAssertRecorder() { this.captured = []; } PowerAssertRecorder.prototype._capt = function _capt(value, espath) { this.captured.push({ value: value, espath: espath }); return value; }; PowerAssertRecorder.prototype._expr = function _expr(value, source) { return { powerAssertContext: { value: value, events: this.captured }, source: source }; }; return PowerAssertRecorder; }();

exports.hello = hello;
// application code use `assert` module
var assert = require("assert");
function hello(name) {
    var _rec = new _powerAssertRecorder();

    assert(_rec._expr(_rec._capt(_rec._capt(typeof name === "undefined" ? "undefined" : _typeof(name), "arguments/0/left") === "string", "arguments/0"), {
        content: "assert(typeof name === \"string\")",
        filepath: "src/index.js",
        line: 4
    }));
    return "Hello " + name;
}
//# sourceMappingURL=index.js.map

_rec._expr return object.

    var assert = require("assert");
    var object = _rec._expr(_rec._capt(_rec._capt(typeof name === "undefined" ? "undefined" : _typeof(name), "arguments/0/left") === "string", "arguments/0"), {
        content: "assert(typeof name === \"string\")",
        filepath: "src/index.js",
        line: 4
    });
    assert(object);

So, assert(Object) never throw error. It causes this issue.

Do you have any solution?

[twada]

@azu Thank you for reporting.
Ah, that's a problem... One thing I can do is, to convert require('assert') to require('power-assert').
I'll create a small babel plugin to do the transpilation.
Thanks!

[twada]

@azu Just created and published babel-plugin-empower-assert to solve this problem. Would you give it a try?

[twada]

Made a pull-req for you.

[azu]

@twada Thanks. work fine.

I think that this issue should be added to FAQ, because this solution is opt-in.
If a user encounter this issue, the user see FAQ at first, I think.

[twada]

I think that this issue should be added to FAQ, because this solution is opt-in.
If a user encounter this issue, the use see FAQ at first, I think.

Yeah exactly!

[twada]

FYI: if you are using Babel, you can use babel-plugin-empower-assert to solve this problem.

With babel-plugin-empower-assert, you can enhance normal assert with .babelrc settings below.

{
  "presets": [
    . . .
  ],
  "env": {
    "development": {
      "plugins": [
        "babel-plugin-empower-assert",
        "babel-plugin-espower"
      ]
    }
  }
}

[twada]

Added to FAQ as How to deal with assert calls in production.

[azu]

Thanks again.

[twada]

You're welcome ;)