Add jest plugin and settings

[weltenwort]

This extracts the ui-specific eslint settings from elastic/kibana so they can
be applied to other repositories as well.

[kimjoar]

When this is merged, can you push a new version and create PRs for core and xpack?

[spalger]

I use the kibana presets in non-kibana projects that I really don't want to depend on jest. Can we add this as a supplementary config that needs opt-in via extends?

if it exposed a jest.js file at the root of the package this should work:

---
extends:
  - "@elastic/kibana"
  - "@elastic/kibana/jest"

[kimjoar]

-1 from me. imo this is the Kibana eslint config, and should be optimized for those projects (It's not a big deal, but we shouldn't have to think about this when adding other plugins later either imo)

[kimjoar]

(Though, maybe it makes sense if there are other elastic projects that rely on them but not jest? Open to the idea)

[spalger]

(Though, maybe it makes sense if there are other elastic projects that rely on them but not jest? Open to the idea)

That's what I'm describing, other elastic js projects that reuse the kibana config but aren't using jest. We can improve that after this is merged though, LGTM

[kimjoar]

Ah, I misunderstood the "non-kibana projects" part. Works for me.

[weltenwort]

@spalger makes sense, thanks for the suggestion. I updated the PR.

[weltenwort]

When adding some documentation I noticed that we are referencing the config as @elastic/kibana in Kibana's root .eslintrc even though the documentation states:

The module name can also be customized, just note that when using scoped modules it is not possible to omit the eslint-config- prefix. Doing so would result in package naming conflicts, and thus in resolution errors in most of cases.

Is that something we want to change as well to align with the official docs?

[spalger]

@weltenwort if it works in eslint 3 then I think we should, but pretty sure that was a breaking change added in eslint 4

[weltenwort]

I think specifying the fully qualified name was always supported. There was a breaking change in 4 that disallows shorthands in namespaced packages to fix misbehavior resulting from ambiguities. I will change it in the PR that references this in kibana after this is merged and published.

@spalger any other concerns?

[weltenwort]

replaced by elastic/kibana#13090