require-guard

Prevent files and modules being required more than once. Helps with auto-reloaders or test runners that insist.

npm install require-guard
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Require Guard for Node.js

NPM version Build status

Require Guard is a library for Node.js that prevents files from being required and loaded more than once.

When you find yourself fighting code-reloaders or test runners like Mocha to stop reloading your slow initialization code each cycle, and no one else can help, maybe you can hire the Require Guard.

"Hey, but doesn't Node.js' require itself not require files twice?"
Yes, but those pesky code-reloaders and test runners, for your own good, unload everything between [test] cycles to keep things fresh. For such cases Require Guard is the sliced bread beneath your toast. Run that external process or slow op once and not worry that it gets run again.

Using the Guard

Install with: npm install require-guard

Then you have 3 ways:

  1. Prevent the current file from being reloaded:

    require("require-guard")()
    
  2. Prevent an already loaded library (also takes an array) from being reloaded:

    require("selenium-webdriver")
    require("require-guard")("selenium-webdriver")
    
  3. Prevent an already loaded file (also takes an array) from being reloaded:

    require("./start-browser")
    require("require-guard")("./start-browser")
    

Example of guarding Selenium WebDriver with Mocha attacking

As an example, let's say you're using Mocha with Selenium WebDriver. Because Selenium starts up as fast as an old Lada engine, you'll want to boot it up once when starting Mocha's watcher and then get on your merry way with testing.

./test/browser.js:

require("require-guard")()
var WebDriver = require("selenium-webdriver")
module.exports = new WebDriver.Builder().build()

./test/test.js:

var browser = require("./browser")
describe("The Internet", function() { ... })

Then, while mocha --watch reruns and reruns your tests, your browser will remain open and will get reused.

License to Kill

Require Guard is released under a Lesser GNU Affero General Public License, which in summary means:

  • You can use this program for no cost.
  • You can use this program for both personal and commercial reasons.
  • You do not have to share your own program's code which uses this program.
  • You have to share modifications (e.g bug-fixes) you've made to this program.

For more convoluted language, see the LICENSE file.

Dossier

Andri Möll typed this and the code.
Monday Calendar supported the engineering work.

If you find Require Guard has muscles that need improving, please type to me at andri@dot.ee or create an issue.

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