Babel plugin to encourage reliable programming by writing assertions in production code, and compiling them away from release.
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README.md

babel-plugin-unassert

Babel plugin for unassert: Encourages programming with assertions by providing tools to compile them away.

unassert

Build Status NPM version Dependency Status License

babel-plugin-unassert removes assertions on build. So you can use assertions to declare preconditions, postconditions and invariants.

RELATED MODULES

INSTALL

$ npm install --save-dev babel-plugin-unassert

CAUTION

For Babel 5 or lower, you need to use the 1.2.x release of babel-plugin-unassert.

$ npm install --save-dev babel-plugin-unassert@1.2.0

HOW TO USE

via .babelrc (Recommended)

{
  "presets": [
    ...
  ],
  "env": {
    "production": {
      "plugins": [
        "babel-plugin-unassert"
      ]
    }
  }
}
$ babel /path/to/src/target.js > /path/to/build/target.js

via Babel CLI

$ babel --plugins babel-plugin-unassert /path/to/src/target.js > /path/to/build/target.js

or shortly,

$ babel --plugins unassert /path/to/src/target.js > /path/to/build/target.js

via Babel API

var babel = require('babel-core');
var jsCode = fs.readFileSync('/path/to/src/target.js');
var transformed = babel.transform(jsCode, {
    presets: [...],
    plugins: ['babel-plugin-unassert']
});
console.log(transformed.code);

EXAMPLE

For given math.js below,

'use strict';

var assert = require('assert');

function add (a, b) {
    console.assert(typeof a === 'number');
    assert(!isNaN(a));
    assert.equal(typeof b, 'number');
    assert.ok(!isNaN(b));
    return a + b;
}

Run babel with --plugins unassert to transform code.

$ babel --plugins unassert /path/to/demo/math.js > /path/to/build/math.js

You will see assert calls and declarations disappear.

'use strict';

function add(a, b) {
    return a + b;
}

ES6 module and power-assert support

babel-plugin-unassert supports ES6 module syntax and power-assert.

with .babelrc,

{
  "presets": [
    ...
  ],
  "env": {
    "development": {
      "presets": [
        "babel-preset-power-assert"
      ]
    },
    "production": {
      "plugins": [
        "babel-plugin-unassert"
      ]
    }
  }
}

production code below

import assert from 'assert';

class Calc {
    add (a, b) {
        assert(!(isNaN(a) || isNaN(b)));
        assert(typeof a === 'number');
        assert(typeof b === 'number');
        return a + b;
    }
}

becomes

'use strict';

class Calc {
    add(a, b) {
        return a + b;
    }
}

in production, and produces power-assert messages like

AssertionError:   # example.js:5

  assert(!(isNaN(a) || isNaN(b)))
         | |     |  |  |     |
         | |     |  |  true  NaN
         | false 3  true
         false

in development.

SUPPORTED PATTERNS

Assertion expressions are removed when they match patterns below. In other words, babel-plugin-unassert removes assertion calls that are compatible with Node.js standard assert API (and console.assert).

  • assert(value, [message])
  • assert.ok(value, [message])
  • assert.equal(actual, expected, [message])
  • assert.notEqual(actual, expected, [message])
  • assert.strictEqual(actual, expected, [message])
  • assert.notStrictEqual(actual, expected, [message])
  • assert.deepEqual(actual, expected, [message])
  • assert.notDeepEqual(actual, expected, [message])
  • assert.deepStrictEqual(actual, expected, [message])
  • assert.notDeepStrictEqual(actual, expected, [message])
  • assert.fail(actual, expected, message, operator)
  • assert.throws(block, [error], [message])
  • assert.doesNotThrow(block, [message])
  • assert.ifError(value)
  • console.assert(value, [message])

babel-plugin-unassert also removes assert variable declarations,

  • var assert = require("assert")
  • var assert = require("power-assert")
  • import assert from "assert"
  • import assert from "power-assert"

and assignments.

  • assert = require("assert")
  • assert = require("power-assert")

AUTHOR

OUR SUPPORT POLICY

We support Node under maintenance. In other words, we stop supporting old Node version when their maintenance ends.

This means that any other environment is not supported.

NOTE: If babel-plugin-unassert works in any of the unsupported environments, it is purely coincidental and has no bearing on future compatibility. Use at your own risk.

LICENSE

Licensed under the MIT license.