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Showing content from https://github.com/unassert-js/babel-plugin-unassert below:

unassert-js/babel-plugin-unassert: Babel plugin to encourage reliable programming by writing assertions in production code, and compiling them away from release.

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

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

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

Babel7 is incompatible with Babel6. Babel6 is incompatible with Babel5.

For Babel6, you need to use the 2.x release of babel-plugin-unassert.

$ npm install --save-dev babel-plugin-unassert@2

For Babel 5 or lower, you need to use the 1.x release of babel-plugin-unassert.

$ npm install --save-dev babel-plugin-unassert@1

const presets = ['@babel/env'];
const plugins = [];

if (process.env.NODE_ENV === 'production') {
  plugins.push('babel-plugin-unassert');
}

module.exports = { presets, plugins };
$ babel /path/to/src/target.js > /path/to/build/target.js

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

const babel = require('@babel/core');
const transformed = babel.transformFileSync('/path/to/src/target.js', {
  presets: ['@babel/env'],
  plugins: ['babel-plugin-unassert']
});
console.log(transformed.code);

For given math.js below,

'use strict';

const 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-cli with --plugins babel-plugin-unassert option to transform.

$ babel --plugins babel-plugin-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.

For given babel.config.js,

module.exports = function (api) {
  const presets = ['@babel/env'];
  const plugins = [];

  if (api.env(['development', 'test'])) {
    presets.push('babel-preset-power-assert');
  }

  if (api.env('production')) {
    plugins.push('babel-plugin-unassert');
  }

  return {
    presets,
    plugins
  };
};

and 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;
  }
}

then it becomes in production,

'use strict';

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

and in development, produces power-assert messages like below

AssertionError:   # example.js:5

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

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).

babel-plugin-unassert also removes assert variable declarations such as,

and assignments.

You can customize Plugin Options such as assertion patterns.

input:

'use strict';

var invariant = require('invariant');
const nassert = require('nanoassert');
import * as uassert from 'uvu/assert';


function add (a, b) {
    nassert(!isNaN(a));

    uassert.is(Math.sqrt(4), 2);
    uassert.is(Math.sqrt(144), 12);
    uassert.is(Math.sqrt(2), Math.SQRT2);

    invariant(someTruthyVal, 'This will not throw');
    invariant(someFalseyVal, 'This will throw an error with this message');

    return a + b;
}

output:

'use strict';

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

via Config Files

{
  "presets": [
    ...
  ],
  "plugins": [
    ["babel-plugin-unassert", {
      "variables": [
        "assert",
        "invariant",
        "nassert",
        "uassert"
      ],
      "modules": [
        "assert",
        "node:assert",
        "invariant",
        "nanoassert",
        "uvu/assert"
      ]
    }]
  ]
}

or via @babel/register.

require('@babel/register')({
  presets: [...],
  plugins: [
    ['babel-plugin-unassert', {
      variables: [
        'assert',
        'invariant',
        'nassert',
        'uassert'
      ],
      modules: [
        'assert',
        'node:assert',
        'invariant',
        'nanoassert',
        'uvu/assert'
      ]
    }]
  ]
});

or via '@babel/core',

const babel = require('@babel/core');
const jsCode = fs.readFileSync('/path/to/test/some_test.js');
const transformed = babel.transform(jsCode, {
  presets: [...],
  plugins: [
    ['babel-plugin-unassert', {
      variables: [
        'assert',
        'invariant',
        'nassert',
        'uassert'
      ],
      modules: [
        'assert',
        'node:assert',
        'invariant',
        'nanoassert',
        'uvu/assert'
      ]
    }]
  ]
});
console.log(transformed.code);
type default value object objects shown below

Configuration options for babel-plugin-unassert. If not passed, default options will be used.

{
  variables: [
    'assert'
  ],
  modules: [
    'assert',
    'power-assert',
    'node:assert'
  ]
}

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.

Licensed under the MIT license.

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