Webpack: Throw error on missing member import

Question

I have an import something like this:

import { foo } from 'bar';

Is there a way to get Webpack to throw an error if foo is not defined?

Note that I'm using Babel if that makes a difference.

Answer 1

As Tobias K pointed out in the comments, the other answer is incorrect. Configuring strictModuleExceptionHandling: true will not produce a compile time error if you try to import a module which does not exist.

The correct configuration is strictExportPresence: true, which is only available in webpack v2.3.0 and later. (Earlier versions can only show a warning, not an error.)

Answer 2

It is possible to configure webpack 2 to throw an error when an import fails by using output.strictModuleExceptionHandling. The functionality was added by this pull request https://github.com/webpack/webpack/pull/3302 but it has not been documented yet. Here's how to use it:

module.exports = {
    entry: {
        main: "./main.js",
    },
    output: {
        filename: "[name].bundle.js",
        strictModuleExceptionHandling: true
    }
}

Now if I try to import from a file which dosn't exist, or I make an import which resolves to undefined I would get error and warning messages in the webpack console:

WARNING in ./js/pedigree.js
32:35-49 "export 'default' (imported as 'DisorderLegend') was not found in './disorderLegend'

ERROR in ./js/pedigree.js
Module not found: Error: Can't resolve './OkCancelDialogue' in '/home/tim/workspace/projects/public/js/ext-lib/panogram/js'
 @ ./js/pedigree.js 5:0-54
 @ ./js/viewerPedigree.js
 @ ./main.js
 @ multi (webpack)-dev-server/client?http://localhost:8080 ./main.js
webpack: Failed to compile.

In the chrome console you'll get a warning like this: