TypeError: Cannot read property 'length' of undefined

[wind4gis]

Describe the bug

A 💯 way to do this is to provide your configuration via a GitHub gist and/or to use markdown when describing which commands you used when the error occurred! Be precise and clear in your description of the bug.

What is the current behavior?
when I run webpack --mode development(or production), the webpack-cli shows TypeError: Cannot read property 'length' of undefined on the line node_modules\webpack-cli\bin\cli.js:93. my computer is win10

This is where you elaborate on the current behavior of the cli, how it behaves normally differing from the previous version/build you did.

To Reproduce
Steps to reproduce the behavior:

1. Go to '...'
2. Click on '....'
3. Scroll down to '....'
4. See error

1.just create a folder on win10
2.npm i -S webpack@next
3.npm i -S webpack-cli@latest
4.write "dev": "webpack --mode development" in package.json
5.npm run dev

Expected behavior
A clear and concise description of what you expected to happen.

Screenshots
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Please paste the results of webpack-cli info here, and mention other relevant information

Additional context
Add any other context about the problem here like linking to an similar issue you might think is the cause.

[evenstensberg]

Hi, thanks for submitting an issue. It's a bug, I've done a patch here:

#1024

Which hopefully will land as a patch soon

[wind4gis]

@evenstensberg It seems that there is still this bug

[evenstensberg]

Could you try out the #1024 branch and check if it fixes the bug?

[ryanspice]

I ran into this issue and pulled your branch it seems to be working now.

[ryanspice]

@evenstensberg not sure if this is to be expected but an empty webpack config object
brings up the same error.

[ryanspice]

actually it might be something else, not quite sure, but trying to plug in my existing config I have seen this error pop up.

[ryanspice]

yeah im not sure why but when i tried to run it with a config now it was always giving me this error

it looks like webpackConfigurationValidationErrors is returning undefined??

it runs if i modify a file

[evenstensberg]

yes, options might be null / undefined, so the error is from validating the schema. Do you think you can figure out when the options obj is nil @ryanspice ?

[ryanspice]

@evenstensberg yeah it seems like validateschemea.js on webpack@5.0.0-alpha.20 doesnt have a return

[evenstensberg]

@sokra can we have that?

[ryanspice]

I created a bug report: webpack/webpack#9591

I was gonna create a branch and make a PR but then I realised I dont think i can do that there.

[sokra]

The validateSchema API changed a bit, since we are using schema-util now. It throws a ValidationError when validation failed. Also note that the name of the validation error changed from WebpackOptionsValidationError to ValidationError.

[evenstensberg]

Do you have a proposed way of using the schema with the new api? Not getting a message from validating the schema as of:

const validateSchema = require("webpack").validateSchema;
const ValidationError = require("webpack").validate;

const webpackConfigurationValidationErrors = validateSchema(webpackConfigurationSchema, options);
if (webpackConfigurationValidationErrors.length) {
       const error = ValidationError(webpackConfigurationValidationErrors);
        console.error(error.message);
	process.exit(-1);
}

[sokra]

try {
  validateSchema(webpackConfigurationSchema, options);
} catch(error) {
  console.error(error.message);
  process.exit(-1);
}

[sokra]

If you want to support both version maybe like this:

let error;
try {
  const errors = validateSchema(webpackConfigurationSchema, options);
  if(errors && errors.length > 0) {
    const WebpackOptionsValidationError = require("webpack").WebpackOptionsValidationError;
    error = new WebpackOptionsValidationError(errors);
  }
} catch(err) {
  error = err;
}

if(error) {
  console.error(error.message);
  process.exit(-1);
}

[ryanspice]

I'm not quite sure I understand why returning the value isn't appropriate.. It returns an empty array with no errors, would it not have an array populated with errors if there were some?
I probably just don't understand a fundamental part like how it would set the value if its not returning anything in the first place.

[ryanspice]

@sokra @evenstensberg no? lol

[willgriffiths]

Fixed by #1065. Landed in v3.3.8.