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Run source transform function on node require call

License: Other

JavaScript 100.00%

nodejs require hook

node-hook's Introduction

node-hook

Run source transform function on Node require

Install and use

npm install --save node-hook

Before loading desired .js files, install hook

var hook = require('node-hook');

function logLoadedFilename(source, filename) {
    return 'console.log("' + filename + '");\n' + source;
}
hook.hook('.js', logLoadedFilename);
require('./dummy');
// prints fulle dummy.js filename, runs dummy.js

hook.unhook('.js'); // removes your own transform

remember: Nodejs caches compiled modules, so if the transform is not working, you might need to delete the cached entry in require.cache, then call require(filename) again to force reload.

Related: Node require replacement really-need.

You can hook several transformers thanks to the code submitted by djulien

Existing transform

You can get the current transform and run any source through it. For example to see how the current source looks when loaded but before evaluated

const filename = resolve('./call-foo.js')
const transform = Module._extensions['.js']
const fakeModule = {
  _compile: source => {
    console.log('transformed code')
    console.log(source)
  }
}
transform(fakeModule, filename)

Small print

License: MIT - do anything with the code, but don't blame me if it does not work.

Support: if you find any problems with this module, email / tweet / open issue on Github

node-hook's People

Contributors

Stargazers

Watchers

Forkers

ahmedshuhel djulien msn0 jeffhatt christianulbrich harrysolovay

node-hook's Issues

Warn if no code is returned

it should warn if the hook function does not return anything (can cause weird bugs)

const hook = require('node-hook')
function instrument(source, filename) {
  console.log('instrumenting %s for data-cover', filename)
  // returns undefined
}
hook.hook('.js', instrument)
process.on('exit', function () {
  console.log('data-cover is done')
  hook.unhook('.js')
})

Document calling original hook

Interesting how to get the original transform function, document in README

relative paths break?

I'm using the following test code, and am getting an interesting error.

var hook = require('node-hook');
function preprocess(source, filename) {
  return source;
}
['js','jsx'].forEach(function(ext) { hook.hook('.' + ext, preprocess); });

Pretty straight-forward pass-through processing, the expectation is that this, of course, does nothing. Instead, it causes and error on the following line later in the same file (line 19 in the file) :

...
var RouteSet = require('../lib/site/routes');
...

Claiming:

module.js:328
    throw err;
    ^

Error: Cannot find module '../lib/site/routes'
    at Function.Module._resolveFilename (module.js:326:15)
    at Function.Module._load (module.js:277:25)
    at Module.require (module.js:354:17)
    at require (internal/module.js:12:17)
    at Object.<anonymous> (J:\Junctions\Users\Mike\Documents\Git projects\projects\BezierInfo-2\pages\test.js:19:16)
    at Module._compile (module.js:398:26)
    at Object.Module._extensions..js (module.js:405:10)
    at Module.load (module.js:344:32)
    at Function.Module._load (module.js:301:12)
    at Function.Module.runMain (module.js:430:10)

Without node-hook, this works just fine, it's just a relative file location, but with node-hook, things no longer work for relative requirements... I tried to change it to ../lib/sites/routes.js because maybe the automatic extension from node's site isn't kicking in, but that just gives the same error:

module.js:328
    throw err;
    ^

Error: Cannot find module '../lib/site/routes.js'
    at Function.Module._resolveFilename (module.js:326:15)
    at Function.Module._load (module.js:277:25)
    at Module.require (module.js:354:17)
    at require (internal/module.js:12:17)
    at Object.<anonymous> (J:\Junctions\Users\Mike\Documents\Git projects\projects\BezierInfo-2\pages\test.js:19:16)
    at Module._compile (module.js:398:26)
    at Object.Module._extensions..js (module.js:405:10)
    at Module.load (module.js:344:32)
    at Function.Module._load (module.js:301:12)
    at Function.Module.runMain (module.js:430:10)

Cannot read property '.js' of undefined

Hi,

I am trying to hook a function in node module, but I got error as mentioned in the title, below is my code:

var hook = require('node-hook');
function Request(method, url) {
alert(url);
}
hook.hook('.js', Request);
require('./node_modules/module_name/index');

Is it possible on the way I am trying to archive?

commit to semver and release v1

I'd like to be able to depend on node-hook@^1.0.0 to make upgrading deps across my whole project easier.

Add option to bust cache

Probably delete all loaded modules that match the extension

Start testing in multiple Node versions

Using autochecker

Add semantic release

And badge

require of JSON returns empty object

On the line 73 is called _compile() and it results into empty object when the content of required module is JSON. I changed my code and assign result of JSON.parse() directly to exports, if extension is '.json'. I'm not sure if it is correct fix and maybe it brings other issues.

not working when server code is precompiled

I've been using this plugin on the server to help render universal apps. The app requires in some code that imports scss, which on the server, is duly ignored. This works find when i was running the server and the first step was to call babel-core/register.

Now that I am trying to remove babel from my prod code i find that the hook is no longer working. By removing babel from my prod code I mean instead i use babel-cli to precompile the server. I then get node to run the compiled code.

I noticed you mentioned clearing cache in your readme; but i don't believe the cache is the problem as the error message suggests the hook isn't doing anything :

Error: Cannot find module './mainLayout.scss'

It seems to me babel register and babel-cli compile in different ways, which doesn't sound right?

have you any idea?

To help, here is a quick place to see that code changes I've made to my app :
https://github.com/peter-mouland/react-lego/compare/remove-prod-babel

the whole app (with this new branch) is available here:
https://github.com/peter-mouland/react-lego/tree/remove-prod-babel

Check if there is registered extension before unhooking

If we try to unhook our hook without registering, causes a crash

const hook = require('node-hook')
process.on('exit', function () {
  console.log('data-cover is done')
  hook.unhook('.js')
})

node_modules/node-hook/index.js:88
  nestedTransforms[extension].pop(); //assumes no stack underflow
                             ^
TypeError: Cannot read property 'pop' of undefined
    at Object.unhook (node_modules/node-hook/index.js:88:30)