Handle undefined tag

[pfhayes]

I have observed this error:

Cannot read property '0' of undefined
TypeError: Cannot read property '0' of undefined
    at EventEmitter.JSXAttribute (/Users/patrick/sigopt-api/node_modules/eslint-plugin-react/lib/rules/forbid-component-props.js:51:16)
    at emitOne (events.js:101:20)
    at EventEmitter.emit (events.js:188:7)
    at NodeEventGenerator.enterNode (/Users/patrick/sigopt-api/node_modules/eslint/lib/util/node-event-generator.js:40:22)
    at CodePathAnalyzer.enterNode (/Users/patrick/sigopt-api/node_modules/eslint/lib/code-path-analysis/code-path-analyzer.js:608:23)
    at CommentEventGenerator.enterNode (/Users/patrick/sigopt-api/node_modules/eslint/lib/util/comment-event-generator.js:97:23)
    at Controller.enter (/Users/patrick/sigopt-api/node_modules/eslint/lib/eslint.js:918:36)
    at Controller.__execute (/Users/patrick/sigopt-api/node_modules/eslint/node_modules/estraverse/estraverse.js:397:31)
    at Controller.traverse (/Users/patrick/sigopt-api/node_modules/eslint/node_modules/estraverse/estraverse.js:501:28)
    at Controller.Traverser.contMakefile:37: recipe for target 'eslint' failed

[ljharb]

Could you provide a test that fails without this change?

[pfhayes]

Here is a minimal example that causes the error for me:

const Parent = React.createClass({
  render: function() {
    return <Child a={this.props.a}/>;
  }
});

However, I tried adding this as a test and the test appears to pass with the existing code. I'm not sure what would cause this or how to induce this error in test-mode, but I can repeatedly generate this error in my environment.

[ljharb]

Is your environment in strict or sloppy mode?

[pfhayes]

How do I check that? I assume it is whatever the default is because I haven't configured anything like that to my knowledge

[ljharb]

@pfhayes if you have 'use strict', or if you've configured eslint to use sourceType modules, then it's in strict mode. Otherwise it'd be in sloppy mode.

If you add 'use strict'; to the top of the test code, does it fail?

[pfhayes]

I don't believe I have configured eslint to use sourceType modules because I do not know how to do that. I am also not using 'use strict'

[ljharb]

@pfhayes are you using babel? any code inside class, or any file using import or export is automatically in strict mode.

[pfhayes]

Yes, the code is being compiled with babel. The example provided has no imports/exports or class declarations (the example provided was the entire contents of the file that introduced the error)

I tried to reproduce this error recently and was unable to. I'm not sure what the cause was - perhaps an error in a dependent module that was fixed by an npm install. i'm fine closing this

[EdwardDrapkin]

Here's one way to replicate it:

foo(bar) {
    return <bar.baz className="error goes here" />;
}

[lencioni]

Thanks for the contribution. Feel free to re-open with a test!

[xeodou]

Got the exactly the same issue here , seems @pfhayes 's PR been closed, but issue still exist. So how do I solve this @lencioni ?

[ljharb]

@xeodou if you can provide a test case in a PR, or better, a test case with a fix, then we'd love to merge it!

[xeodou]

Sure @ljharb i'll do.

[xeodou]

Hi @ljharb I just found the use case and create pull request, please feel free to make some comments.