v4.14.0 scope analysis issue with babel-eslint

[steida]

For some reason, after update:

ERROR  Failed to compile with 1 errors                                                                                                    00:04:50
error  in ./pages/_document.js?entry

Module build failed: TypeError: Cannot read property 'type' of undefined
    at isForInRef (/Users/steida/dev/este/node_modules/eslint/lib/rules/no-unused-vars.js:410:24)
    at variable.references.some.ref (/Users/steida/dev/este/node_modules/eslint/lib/rules/no-unused-vars.js:447:21)
    at Array.some (<anonymous>)
    at isUsedVariable (/Users/steida/dev/este/node_modules/eslint/lib/rules/no-unused-vars.js:446:40)
    at collectUnusedVariables (/Users/steida/dev/este/node_modules/eslint/lib/rules/no-unused-vars.js:569:26)
    at Program:exit (/Users/steida/dev/este/node_modules/eslint/lib/rules/no-unused-vars.js:621:36)
    at listeners.(anonymous function).forEach.listener (/Users/steida/dev/este/node_modules/eslint/lib/util/safe-emitter.js:47:58)
    at Array.forEach (<anonymous>)
    at Object.emit (/Users/steida/dev/este/node_modules/eslint/lib/util/safe-emitter.js:47:38)
    at NodeEventGenerator.applySelector (/Users/steida/dev/este/node_modules/eslint/lib/util/node-event-generator.js:251:26)

[eslint-deprecated]

Hi @steida, thanks for the issue. It looks like there's not enough information for us to know how to help you.

If you're reporting a bug, please be sure to include:

1. The version of ESLint you are using (run eslint -v)
2. What you did (the source code and ESLint configuration)
3. The actual ESLint output complete with numbers
4. What you expected to happen instead

Requesting a new rule? Please see Proposing a New Rule for instructions.

Requesting a rule change? Please see Proposing a Rule Change for instructions.

If it's something else, please just provide as much additional information as possible. Thanks!

[steida]

4.13.1

[ilyavolodin]

Could you provide a sample of the code where this is failing?

[steida]

https://github.com/este/este

yarn deps to update eslint

Sorry I have no more details.

[platinumazure]

@steida Try eslint --debug so you can see what file it's running on before crashing. Then you could provide the contents of that file, or try to narrow it down further. Without a code sample, there's not much we can investigate unless someone is willing to take the time to clone your repo... Thanks for understanding!

[steida]

Sure. Once I figure out how to run debug mode within webpack integration.

at Object.emit (/Users/steida/dev/este/node_modules/eslint/lib/util/safe-emitter.js:47:38)
    at NodeEventGenerator.applySelector (/Users/steida/dev/este/node_modules/eslint/lib/util/node-event-generator.js:251:26)

 @ multi ./pages/_document.js?entry

(node:80698) DeprecationWarning: Module.chunks: Use Module.forEachChunk/mapChunks/getNumberOfChunks/isInChunk/addChunk/removeChunk instead

[steida]

Sorry, I don't know how to run eslint in debug mode from eslint-loader. Maybe later...

[le0nik]

Here's a minimal example of code it's failing on in my case with the same error. It doesn't fail i remove @myDecorator line or use eslint@<=4.13.1. Parser is set to babel-eslint@8.0.3.

function myDecorator(SomeClass) {
  return SomeClass;
}

@myDecorator
class MyClass {
}

[not-an-aardvark]

@le0nik Thanks, that's very useful info. Are you able to reproduce the issue without babel-eslint? It's possible this is caused by something that babel-eslint is doing to modify ESLint's scoping behavior. (Actually, in this release we created a new scoping API so that parsers wouldn't need to monkeypatch scoping behavior, but it's possible that we broke some existing interactions with the changes we made internally for that API.)

[dashed]

Getting similar issues with flow code.

$ yarn lint
yarn run v1.3.2
$ eslint src test
Cannot read property 'type' of undefined
TypeError: Cannot read property 'type' of undefined

....

[le0nik]

@not-an-aardvark it doesn't work with decorators without babel-eslint. I get

5:1  error  Parsing error: Unexpected character '@'

[not-an-aardvark]

@le0nik To clarify, I was trying to ask if this issue occurs when you're neither using babel-eslint nor non-standard syntax. (As you noticed, if you only remove babel-eslint then the default parser won't be able to parse your code.)

[not-an-aardvark]

cc @mysticatea

[le0nik]

@not-an-aardvark Just removed all uses of decorators in my project. In this case there is no error with and without babel-eslint.

[not-an-aardvark]

Also see: babel/babel-eslint#542

[not-an-aardvark]

This issue should be fixed if you upgrade to the latest version of babel-eslint.

[ndelangen]

@not-an-aardvark I tried babel-eslint 8.1.0 and was still experiencing the issue.

I've downgraded to eslint 4.13.0 for now.

Opened a babel-eslint ticket here:
babel/babel-eslint#558

[mikeconwell]

@not-an-aardvark , We are using a number of babel* products, but not babel-eslint, and experience same issue with 4.14.0. Having to lock in at 4.13.1.

Edit: babel-eslint was installing as dependency of an internal eslint clone.

[not-an-aardvark]

@mikeconwell Would you mind creating a new issue with more information?

[mikeconwell]

@not-an-aardvark I'll put the work on that team to update dependencies citing this task. May come back later. Thanks for quick response.