ES6 modules: TypeError: Cannot read property 'type' of undefined

[badsyntax]

Hi.

I'm using 0.17.0, and I have the following code in a file test.js:

import EventEmitter from 'events';

I have the following eslint config:

"env": {
  "es6": true
},
"ecmaFeatures": {
  "modules": true
}

When running eslint on that file I get the following error: TypeError: Cannot read property 'type' of undefined

Exporting or referencing that object fixes the error:

import EventEmitter from 'events';

export default class Base extends EventEmitter {
  method() {
    return 'foo';
  }
}

Setting a property now causes a different error TypeError: Cannot read property 'name' of undefined:

import EventEmitter from 'events';

export default class Base extends EventEmitter {
  method() {
    this.foo = 'bar';
  }
}

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[btmills]

Stack trace for TypeError: Cannot read property 'type' of undefined puts the error at no-unused-vars line 43, which is if (definition.type === "VariableDeclarator") {.

Stack trace for TypeError: Cannot read property 'name' of undefined puts the error at no-func-assign line 42, which is if (def.name.name === name && def.type === "FunctionName") {.

[benmosher]

I'm seeing the no-func-assign issue on a number of files that were linting properly with v0.16.x, as well.

[nzakas]

@benmosher one big report per issue, please.

[btmills]

Technically #2071 is a duplicate of this issue, though it reports the no-func-assign error first, so let's use this issue for no-unused-vars and #2071 for no-func-assign.

[btmills]

Working on this.

[btmills]

The no-unused-vars error only occurs when no-undef is also enabled.

config.json:

{
    "env": {
        "es6": true
    },
    "ecmaFeatures": {
        "modules": true
    },
    "rules": {
        "no-undef": 2,
        "no-unused-vars": [2, {"vars": "all", "args": "after-used"}],
    }
}

// test.js
import foo from 'foo';

$ eslint --reset --no-eslintrc -c config.json test.js
~/code/eslint/eslint/lib/rules/no-unused-vars.js:43
            if (definition.type === "VariableDeclarator") {
                          ^
TypeError: Cannot read property 'type' of undefined
    at isExported (~/code/eslint/eslint/lib/rules/no-unused-vars.js:43:27)
    at EventEmitter.Program:exit (~/code/eslint/eslint/lib/rules/no-unused-vars.js:120:70)
    at EventEmitter.emit (events.js:129:20)
    at Controller.controller.traverse.leave (~/code/eslint/eslint/lib/eslint.js:743:25)
    at Controller.__execute (~/code/eslint/eslint/node_modules/estraverse/estraverse.js:393:31)
    at Controller.traverse (~/code/eslint/eslint/node_modules/estraverse/estraverse.js:481:28)
    at EventEmitter.module.exports.api.verify (~/code/eslint/eslint/lib/eslint.js:728:24)
    at processFile (~/code/eslint/eslint/lib/cli-engine.js:193:27)
    at ~/code/eslint/eslint/lib/cli-engine.js:293:26
    at walk (~/code/eslint/eslint/lib/util/traverse.js:81:9)

Removing either of the rules from config.json will fail to cause the crash.

[btmills]

The fixImport hack temporarily added in #2035 isn't properly cleaning up after itself.

[badsyntax]

Thanks! I've tested this change with 0.17.1 and it's now working as expected 👍

[benmosher]

I am also not seeing a crash anymore, but no-unused-vars no longer highlights unused import specifiers in 0.17.1. Is this expected, given the escope workaround?

(I thought about opening a new issue, but I'm not clear on whether this is understood behavior.)

FWIW: updating to escope 2.0.7 does seem to fix it, but breaks the "Edge cases should not crash when parsing destructured assignment" test.

[nzakas]

Please file a new issue and provide sample code plus console output.

[benmosher]

Done: #2114