Nest: Bundle generated by Webpack throws: Please, make sure to install this library ($ npm install class-validator)

[IskanderMustafin]

Any solution or workaround on this?

Sorry for being impatient, but this really stops me from using Nest. I want to have comfortable development experience using Webpacks's HotModuleReplacementPlugin like explained in this official tutorial: https://docs.nestjs.com/techniques/hot-reload

People complaining about loadPkg function:

class-validator is loaded by loadPkg function in validation.pipe.js:

classValidator = loadPkg('class-validator');

That's why webpack cant resolve class-validator. Does anyone have a good solution?

[shajeeck]

Any solution or workaround on this?

Sorry for being impatient, but this really stops me from using Nest. I want to have comfortable development experience using Webpacks's HotModuleReplacementPlugin like explained in this official tutorial: https://docs.nestjs.com/techniques/hot-reload

People complaining about loadPkg function:

class-validator is loaded by loadPkg function in validation.pipe.js:
classValidator = loadPkg('class-validator');
That's why webpack cant resolve class-validator. Does anyone have a good solution?

is your case because of absence of class-validator package? if so you can install by
npm i --save class-validator class-transformer

[IskanderMustafin]

:) thanks for advice, But first thing I tried is to install different versions of both packages (first time I installed actual packages [_current version_], then I tried to install explicitly versions of packages mentioned in official tutorials: cats app and Webpack example) . But still problem didn't gone.

As I mentioned before: I think people is right and problem is deeper - probably it related to framework's specific way of loading packages (Nest's custom method loadPkg) and Webpack,

[Legiew]

Hey,
I have the same issue, but with the fastify package. We use the FastifyAdapter and if I build with webpack, I got the error "[PackageLoader] The "fastify" package is missing. Please, make sure to install this library ($ npm install fastify) to take advantage of FastifyAdapter."
Anyone has a solution to this?

[Legiew]

We found a solution to this. If you have a look at the not minified webpack generated js code you will find something like this:

function loadPackage(packageName, context) {
    try {
        return __webpack_require__(149)(packageName);
    }
    catch (e) {
        logger.error(MISSING_REQUIRED_DEPENDENCY(packageName, context));
        process.exit(1);
    }
}

This is causing the thrown error. So we dive deeper in the __webpack_require__(149). The number should be different for you but you can easily search for it. It should only be visible one more time in the js code.

/* 149 */
/***/ (function(module, exports) {

function webpackEmptyContext(req) {
    var e = new Error("Cannot find module '" + req + "'");
    e.code = 'MODULE_NOT_FOUND';
    throw e;
}
webpackEmptyContext.keys = function() { return []; };
webpackEmptyContext.resolve = webpackEmptyContext;
module.exports = webpackEmptyContext;
webpackEmptyContext.id = 149;

/***/ }),

Webpack per default replaces all require() calls with it's own logic like above.
The nestjs code contains a require call which is dynamic so webpack is not able to resolve it at compile time but still replaces it. (https://github.com/nestjs/nest/blob/master/packages/common/utils/load-package.util.ts)

So for the solution we have to tell webpack to just skip this require call and let the application do the normal nodejs require stuff, like traversing node_module folders.

To do this, you npm i string-replace-loader which is a plugin for webpack. Inside your webpack config you add the following under module.rules[]:

{
    test: /load-package\.util\.js$/,
    loader: "string-replace-loader",
    options: {
        search: "require[(]([^'\"])",
        replace: "__non_webpack_require__($1",
        flags: "g",
    },
},

The js code now looks like the following and works:

function loadPackage(packageName, context) {
    try {
        return require(packageName);
    }
    catch (e) {
        logger.error(MISSING_REQUIRED_DEPENDENCY(packageName, context));
        process.exit(1);
    }
}

If you have more files where you dynamically require libs, you have to add them to the regex.
s. https://www.npmjs.com/package/string-replace-loader

[kamilmysliwiec]

It should be fixed in 6.0.0

[earksiinni]

Can we reopen this? It's not fixed for me in 6.0.5.

[NikitaIT]

i have

"@nestjs/common": {
      "version": "6.2.2",

[Nest] 14640   - 2019-05-24 02:04   [PackageLoader] The "class-transformer" package is missing. Please, make sure to install this library ($ npm install class-transformer) to take advantage of ValidationPipe. +4ms
[0] [nodemon] app crashed - waiting for file changes before starting...



md5-6485f05c6d91bd8f8ac2fdb9241cc41f



npm i class-transformer --save

[kamilmysliwiec]

It's not an issue. class-transformer is and will always be required if you use ValidationPipe

[bartekczyz]

@kamilmysliwiec actually this __is__ an issue. I've created empty project and trying to bundle it using webpack. I get class-transformer errors as well as many others

[cryptosalomao]

I'm getting this error on the current version, even when already installed class-validator.

[Legiew]

Can you try my solution from above?
s. https://github.com/nestjs/nest/issues/1386#issuecomment-461914216
It should also work in version 6.x, but I don't tested it.

If this works it maybe will be a good idea to put a hint in the docs how to solve this problem.

[RedaKhyatti]

I'm getting that same issue on a mono-repo project when trying to import libraries that use class-validator into an app. Any suggestion how to overcome that error in a nest mono-repo project?

[lock[bot]]

This thread has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.