Add ESLint rule playground

[gaearon]

I found it rather annoying to iterate on our lint rules. Www/Nuclide has been too slow, and tests, while nice, make it too cumbersome to experiment with one particular use case, or just explore how the rule "feels" in practice.

This adds a "playground" fixture that lets you edit a file in an editor like VSCode and have any changes to rule source be reflected immediately on recheck. I had to make a hacky "proxy" rule for that to work because Node would cache the actual rule normally. The resulting workflow is pretty nice and I want to check this in — it'll definitely be useful to me but maybe to someone else too.

Obligatory gif:

[bvaughn]

I don't think this seems to be working for me. Maybe I'm misunderstanding something?

I've ran yarn && yarn start:

When I modify the RulesOfHooks file– this watch re-runs successfully.

But I've opened the fixtures/eslint/index.js file and tried editing it– and nothing happens. No warnings show.

I have VS Code with the ESLint extension installed:

[gaearon]

Did you open react folder in VSCode or react/fixtures/eslint? It seems like it doesn't work unless you open this specific folder as project root. I'll add to README.

[bvaughn]

Ah, that would be it then. I assumed you could open the full react project (since you would also be editing the rule).

[bvaughn]

Looks like it works for me now 👍

[gaearon]

I don't like Code so I'll be editing it in Sublime personally. :-)

But I think you can React as a folder to workspace and then it works.

[bvaughn]

I don't like Code so I'll be editing it in Sublime personally. :-)

I'm also a Sublime user. I only fired up and tested Code because of your readme:

2. "File > Add Folder to Workspace" this specific folder in VSCode with ESLint extension

[gaearon]

I figured most our users are on Code so we should probably test in that in general. Autofix support is nice too.