add support for linting json files

[viankakrisna]

Verified the changes by creating invalid .json file in src and importing it via index.js

{
    some: 'setting'
}

Before:

After:

[viankakrisna]

@Timer seems like this PR doesn't trigger @react-scripts-dangerous, any reasons why?

[Timer]

It hasn't ran in a few days, I might of shut it off on Heroku -- I'm not sure what's up 🤔.

Will probably look at it here soon again because it needs to be working to cut next releases.

[viankakrisna]

@gaearon @Timer @tharakawj will this be merged?

[Timer]

I do like this; we'll schedule it for 2.0.0 just in case there's some weird edge case that breaks JSON in the plugin.

[gaearon]

This looks a bit weird. Can we figure out why this happens and if there's a nicer way to do it?

[viankakrisna]

webpack-contrib/json-loader#44 which links to https://webpack.js.org/guides/migrating/#json-loader-is-not-required-anymore

When no loader has been configured for a JSON file, webpack will automatically try to load the JSON file with the json-loader.

I think adding json test in eslint-loader counts as loader has been configured for a JSON file

[viankakrisna]

@gaearon added a link in the comments about why we need json-loader

[gaearon]

My main concerns are:

1. More complicated post-eject configuration (given that webpack finally handles json by default and it's annoying to have to special-case it again)
2. Performance. If you import huge JSON files, how does this affect the build performance?

[viankakrisna]

1. Yeah, but i think it's a fair tradeoff concerning people that got bitten by debugging json file, when it's big enough and you only given the position is when we needed it the most :)

2. build time comparison between next and json-lint with json file that has 18964 lines

so, yeah, i think this is a no 😄

[gaearon]

That's impacting the build time too much unfortunately.
Maybe there's some other way we can fix it, e.g. by using a better parser in webpack itself?

[viankakrisna]

yeah i thought so, eslint-plugin-json itself is using jshint(!) internally. I'll dig more on the webpack side when i found the time.