Standard reports unfixable errors for Flow code

[strager]

I followed these instructions to set up Standard with Flow support: https://standardjs.com/#can-i-use-a-javascript-language-variant-like-flow-or-typescript

Unfortunately, Standard reports problems I don't know how to fix. For example, in the following code, I have a Flow-annotated class property called _greeting:

// @flow

class Greeter {
  _greeting: string

  constructor () {
    this._greeting = 'hello world'
  }

  greet (): void {
    console.log(this._greeting)
  }
}

new Greeter().greet()

For this code, Standard reports the following problem:

  /Users/mg/Projects/standard-js-flow-issue/index.js:4:3: '_greeting' is not defined.

If I remove line 4 which declares _greeting, Standard no longer reports the problem, but now Flow complains:

Error: index.js:5
  5:     this._greeting = 'hello world'
              ^^^^^^^^^ property `_greeting`. Property not found in
  5:     this._greeting = 'hello world'
         ^^^^ Greeter

Error: index.js:9
  9:     console.log(this._greeting)
                          ^^^^^^^^^ property `_greeting`. Property not found in
  9:     console.log(this._greeting)
                     ^^^^ Greeter


Found 2 errors

How can I make both Standard and Flow happy for this code?

The following script lets you reproduce the problem from scratch: https://gist.github.com/strager/02f2dbebb3a4f5aafeb0b0fa4041936f/b77094b402bb8ed5cb55e304205a206543696b78#file-set_up-sh (That Gist also includes my yarn.lock file so you can see what version of the packages I installed.)

[on3iro]

This is an issue with babel-eslint. Try to downgrade babel-eslint to 8.0.3 then it should work :)

[strager]

@on3iro, thanks! I confirm that running the following command makes yarn run standard --parser babel-eslint --plugin flowtype report no issues:

$ yarn add --dev babel-eslint@8.0.3

Even with this workaround, I'm still having problems with my real project. I'll investigate some more and close this issue if my other problems are unrelated.

[strager]

I think I figured out what's wrong with my project.

Installing lab (a project which I think is unrelated to Standard) re-breaks Standard:

$ yarn add --dev lab
...
$ yarn run standard --parser babel-eslint --plugin flowtype
yarn run v1.3.2
$ /Users/mg/Projects/standard-js-flow-issue/node_modules/.bin/standard --parser babel-eslint --plugin flowtype
standard: Use JavaScript Standard Style (https://standardjs.com)
  /Users/mg/Projects/standard-js-flow-issue/index.js:4:3: '_greeting' is not defined.
error Command failed with exit code 1.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.

lab has a dependency on eslint@4.9.x, and it looks like Standard starts using that version of the eslint package instead of its own version (eslint@~3.19.0).

I'm not very familiar with Node's module system. Is Standard using eslint incorrectly? Is this a bug in Yarn? Is something broken in lab?

I tried to work around this issue by explicitly installing eslint@3.19.0 in my project, but that seemed to have no effect.

$ yarn add --dev eslint@3.19.0
...
$ yarn run standard --parser babel-eslint --plugin flowtype
yarn run v1.3.2
$ /Users/mg/Projects/standard-js-flow-issue/node_modules/.bin/standard --parser babel-eslint --plugin flowtype
standard: Use JavaScript Standard Style (https://standardjs.com)
  /Users/mg/Projects/standard-js-flow-issue/index.js:4:3: '_greeting' is not defined.
error Command failed with exit code 1.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.

Script to reproduce: https://gist.github.com/strager/02f2dbebb3a4f5aafeb0b0fa4041936f/74231871320c68db7dd08be67fb8c0aff80270ef#file-set_up-sh

Side note: Standard's cache is broken. I had to run rm ~/.standard-cache/.cache_* in many cases while figuring out what's wrong.

[strager]

I had the same issue with npm, so I don't think this issue is Yarn's fault:

$ rm -rf node_modules
$ npm install
...
$ ./node_modules/.bin/standard --parser babel-eslint --plugin flowtype
standard: Use JavaScript Standard Style (https://standardjs.com)
  /Users/mg/Projects/standard-js-flow-issue/index.js:4:3: '_greeting' is not defined.

[strager]

With lab installed, installing babel-eslint@7.2.1 makes Standard much more tolerable:

$ yarn add --dev babel-eslint@7.2.1

I have no idea why this works or why babel-eslint@8.0.3 worked without lab.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs.

[feross]

standard v11 (released a few months ago) now uses ESLint 4 internally so perhaps this issue is fixed now?

Edit: Meant v11 instead of v12.

[lithium2013]

@feross Maybe you mean v11 instead of v12?

[feross]

@lithium2013 Yes, I meant v11.