Warning: Critical dependencies.

[fresheneesz]

What does this warning mean? Can this warning give a little more information as to its significance and what you might want to do about it (or perhaps where to find more information about it)?

[sokra]

added better warning message

[fresheneesz]

Ah, so its a warning that one of the dependencies is an expression. Thanks Sokra!

I would suggest that calling it a "critical dependency" doesn't quite describe what it is. Critical dependency makes me think of a dependency that must exist for things to work. Instead, this is simply warning about a dependency written as an expression. I would leave out the words "Critical dependency" and just let "the request of a dependency is an expression" describe it. Its much more understandable now tho.

[kentcdodds]

Would there be a way to suppress this warning for 3rd party libraries? I don't want to get this every time I build just because I have a dependency that does this.

[MarkNijhof]

+1 on suppressing

[jhnns]

Would there be a way to suppress this warning for 3rd party libraries? I don't want to get this every time I build just because I have a dependency that does this.

This error should not be ignored. It usually means that every file below a certain path will be included into the bundle (which should certainly not be ignored).

It always needs to be resolved with aliasing or require contexts

[MarkNijhof]

Can I then suggest the error points to these two links?

On Wednesday, January 28, 2015, Johannes Ewald notifications@github.com
wrote:

Would there be a way to suppress this warning for 3rd party libraries? I
don't want to get this every time I build just because I have a dependency
that does this.

This error should not be ignored. It usually means that every file
below a certain path will be included into the bundle (which should
certainly not be ignored).

It always needs to be resolved with aliasing
http://webpack.github.io/docs/configuration.html#resolve-alias or require
contexts
http://webpack.github.io/docs/configuration.html#automatically-created-contexts-defaults-module-xxxcontextxxx

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[jhnns]

The error message is confusing, yes @sokra.

Unfortunately these problems can not be solved all the same way. It heavily depends on what the library author is trying to achieve, but almost always it can be avoided at all. See #733 and ansman/validate.js#12 (comment)

[MarkNijhof]

But I have no direct influence in how a third party lib does things. Can
this be solved without touching their code? Else a way to supres individual
errors would be great

On Wednesday, January 28, 2015, Johannes Ewald notifications@github.com
wrote:

The error message is confusing, yes @sokra https://github.com/sokra.

Unfortunately these problems can not be solved all the same way. It
heavily depends on what the library author is trying to achieve, but almost
always it can be avoided at all. See #733
#733 and ansman/validate.js#12
(comment)
ansman/validate.js#12 (comment)

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s: marknijhof

[kentcdodds]

@MarkNijhof, I believe that's what @jhnns is saying. Using aliases, require contexts, or some other mechanism, there is a way to fix the issue. webpack is powerful.

[MarkNijhof]

Ah misunderstood, and yes very happy with webpack

On Wednesday, January 28, 2015, Kent C. Dodds notifications@github.com
wrote:

@MarkNijhof https://github.com/MarkNijhof, I believe that's what @jhnns
https://github.com/jhnns is saying. Using aliases, require contexts, or
some other mechanism, there is a way to fix the issue. webpack is powerful.

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[sokra]

Try the ContextReplacmentPlugin...

[MarkNijhof]

Thanks will try tomorrow :-)

On Wednesday, January 28, 2015, Tobias Koppers notifications@github.com
wrote:

Try the ContextReplacmentPlugin...

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[ayozebarrera]

I had the same warning using:

let Class = require(url);

and the warning disappeared when I did the following:

let Class = require(`${url}`);

Should I worry about this thing?

Thanks!

[jhnns]

@ayozebarrera that's strange, because your require() statement stays dynamic. There should still be a warning.

Please be aware of that ES2015 modules won't allow dynamic imports, so there's no upgrade path for your code.

[ayozebarrera]

Yeah it's strange because I have dynamic imports in two different places of my code. But the warning only appeared in this last. So checking the other dynamic import I noticed that the difference is the string... and i.e., there's no warnings from webpack ^^

Thanks for the help, and hope my feedback help you to catch any bug!

[fresheneesz]

ES6 modules don't allow dynamic imports? Isn't that a huge problem in cases of circular dependencies?

[jhnns]

Nope. Dynamic imports and circular dependencies are unrelated. ES2015 is able to handle circular dependencies.

[fresheneesz]

@jhnns I take back what I said, I was using dynamic requires to refer to something else. My bad

[brodo]

Hi, I just got this error because a library I use does do this. Could you maybe add some explanation to the error message? It was not clear to me that "the request of a dependency is an expression" == "there is a dynamic import here and dynamic imports should not be used".

[mmahalwy]

Getting it with:

const loadRouteAsync = path => (nextState, cb) => {
  return System.import(path).then(module => {
    console.log(module);
    cb(null, module)
  });
};

[jhnns]

@mmahalwy The code you're using is too generic, webpack needs to include all files inside the current folder and all files in child folders. Try to make the path more explicit, like System.import("pages/" + path). Webpack has to guess in advance what kind of module you're trying to import by analyzing your source code. If your source code gives no clue, webpack makes all modules in this folder importable.

[seiyria]

So one of the third party libraries I'm using (Tabletop) does this:

  if (typeof process !== 'undefined' && !process.browser) {
    inNodeJS = true;
    var request = require('request'.trim()); //prevents browserify from bundling the module
  }

Does Webpack bundle anything extra as a result, or what should I do to tell Webpack to not make any attempts for this, etc, because this require simply does not need to be resolved.

[Ancientshield]

08:29:10 webpack.1 |                                      Asset       Size       Chunks                         Chunk Names
08:29:10 webpack.1 |     js/application-e6df12ccd2f6f43a2d3c.js   5.65 MiB  application  [emitted] [immutable]  application
08:29:10 webpack.1 | js/application-e6df12ccd2f6f43a2d3c.js.map   5.62 MiB  application  [emitted] [dev]        application
08:29:10 webpack.1 |       js/tagsinput-e4036152fa3328826ac2.js    427 KiB    tagsinput  [emitted] [immutable]  tagsinput
08:29:10 webpack.1 |   js/tagsinput-e4036152fa3328826ac2.js.map    481 KiB    tagsinput  [emitted] [dev]        tagsinput
08:29:10 webpack.1 |                              manifest.json  689 bytes               [emitted]
08:29:10 webpack.1 |
08:29:10 webpack.1 | WARNING in ./node_modules/express/lib/view.js 74:13-25
08:29:10 webpack.1 | Critical dependency: the request of a dependency is an expression
08:29:10 webpack.1 |     at CommonJsRequireContextDependency.getWarnings (/Users/rd/training/node_modules/webpack/lib/dependencies/ContextDependency.js:40:18)
08:29:10 webpack.1 |     at Compilation.reportDependencyErrorsAndWarnings (/Users/rd/training/node_modules/webpack/lib/Compilation.js:1454:24)
08:29:10 webpack.1 |     at /Users/rd/training/node_modules/webpack/lib/Compilation.js:1258:10
08:29:10 webpack.1 |     at AsyncSeriesHook.eval [as callAsync] (eval at create (/Users/rd/start_training/node_modules/tapable/lib/HookCodeFactory.js:33:10), <anonymous>:15:1)
08:29:10 webpack.1 |     at AsyncSeriesHook.lazyCompileHook (/Users/rd/training/node_modules/tapable/lib/Hook.js:154:20)
08:29:10 webpack.1 |     at Compilation.finish (/Users/rd/training/node_modules/webpack/lib/Compilation.js:1253:28)
08:29:10 webpack.1 |     at /Users/rd/training/node_modules/webpack/lib/Compiler.js:672:17
08:29:10 webpack.1 |     at _done (eval at create (/Users/rd/training/node_modules/tapable/lib/HookCodeFactory.js:33:10), <anonymous>:9:1)
08:29:10 webpack.1 |     at eval (eval at create (/Users/rd/training/node_modules/tapable/lib/HookCodeFactory.js:33:10), <anonymous>:20:22)
08:29:10 webpack.1 |     at /Users/rd/training/node_modules/webpack/lib/Compilation.js:1185:12
08:29:10 webpack.1 | ℹ ｢wdm｣: Compiled with warnings.

[smac89]

Such an annoying warning. I solved this by using the following in webpack.config.js:

stats: {
    warningsFilter: [/critical dependency:/i],
}

[ChrisSargent]

I'm working on a lambda application with AWS amplify, hence my need for bundling (so I can't exclude Node Externals for example). I am seeing this error from a package (https://github.com/Nike-Inc/lambda-logger-node) which includes the following code:

function hasModuleLoaded(moduleName) {
  try {
    return !!require.cache[require.resolve(moduleName)]
  } catch (e) {
    if (/Cannot find module/.test(e.toString())) return false
    throw e
  }
}

Also, looking at another npm module, I can see the code does a similar thing which produces this error: https://github.com/kownacki/module-available/blob/master/index.js

"use strict";

module.exports = function(moduleName) {
    if (typeof moduleName !== "string") {
        throw new TypeError("Passed parameter must be a string.");
    }

    try {
        require.resolve(moduleName);
    }
    catch (error) {
        if (error.code === "MODULE_NOT_FOUND") {
            return false;
        }
        throw error;
    }
    return true;
};

It kind of seems a legitimate use case for this kind of requiring so I'm just wondering what the recommended way of handling this could be?

EDIT: Actually, I guess the issue in a 'bundled' app is that require.resolve will always return false. But still, I wonder how to therefore suppress the error using the ContextReplacementPlugin?

[tstibbs]

I've read the many comments on this issue and still can't work out how to get rid of the error. It's fine when it's your own code and you can use require contexts, but if it's in a third-party module that you don't control, then it's harder. In my case, bundling Mocha causes this error, but it still works fine because I don't use any of the functionality that's affected. So, I just want to suppress the warning.

In case it helps anyone else, here's the best I could come up with. It's a dirty hack that looks for the path that mocha is trying to load from (.) and then checks that it is indeed mocha that's trying to load from it, and if so tells it to look for things using a regex that should never match anything.

new webpack.ContextReplacementPlugin(
    /^\.$/,
    (context) => {
        if (/\/node_modules\/mocha\/lib/.test(context.context)) {//ensure we're only doing this for modules we know about
            context.regExp = /this_should_never_exist/
            for (const d of context.dependencies) {
                if (d.critical) d.critical = false;
            }
        }
    }
)

(add the above to plugins in your webpack config)

[macrozone]

I also have this with this library https://github.com/jeanlescure/short-unique-id

i use it in another library and now this "warning" leaks into any consumer of my library, altough nothing seems to be wrong at all.

I have to do something about it, does someone have an idea how to supress it for any consumer of my library?

[johndiiorio]

I wanted to share my own findings in investigating these warnings. In my experience, even though they can be suppressed (e.g. with exprContextCritical: false or by tricking webpack with template literal strings), they are usually indicative of some real issue and should be addressed, especially if they appear suddenly. If you are doing things on the backend, try using webpack-node-externals to not bundle your node_modules. In my case, I switched to a monorepo setup (e.g. Lerna / Yarn workspaces / NPM workspaces) and was using webpack-node-externals, but ran into this issue.