* [kbn-pm] Use yarn workspaces for dependencies (#24095)
* Bumped leadfoot to 1.7.5 now that it issue has been merged. (#17582)
* Copy license to build
I'd really like to upgrade to Typescript 3 for its `unknown` type, but we need to upgrade to `jest@23` to support a recent version of `ts-jest@23`.
The [jest changelog](https://github.com/facebook/jest/blob/master/CHANGELOG.md) breaks down the breaking changes in 23.x, but I found it to be slightly incomplete so I've broken down the changes that actually caused breaks for us here, and addressed each in individual commits to make review a little easier:
- the `testURL` config default was changed from `about:blank` to `http://localhost`
- this cause some XHR requests powered by JSdom to start failing. It seems these requests just do nothing in master but start to fail when JSdom is initialized with an actual URL... I think we would ideally stop sending meaningless XHR requests in the tests, but it was a lot easier to just set the config to `about:blank` for now, and we can worry about cleanup later if necessary
- `expect(...).toThrow()` only passes if an actual error was thrown.
- In two places in the index pattern code we were throwing strings, which broke the assertions. Fortunately/Unfortunately the errors are not being consumed by anything, so I was able to wrap them in `new Error()` without causing any issues.
- snapshots of mock functions now include a `results` array, detailing the return values of the function
- React fragments are now serialized as `<React.Fragment>` instead of `<UNDEFINED>`
- undefined props in React components are now stripped from snapshots
- minor changes to the ordering of mocks, imports resolution, and before hooks caused the uiSettings API tests to start breaking, but I'm replacing them with totally new tests in #22694 so I just deleted them here
- mocks created with `jest.spyOn()` that are restored now have their `mock.calls` reset, so some of the kbn-pm tests stated failing. This was fixed by restoring them with `jest.restoreAllMocks()` rather than trying to do it before the assertions
This upgrades TypeScript to version 2.9.2. My main motivation is the support for generic type arguments in JSX elements and tagged templates (e.g. for `styled-components`).
Problems arising from breaking changes in the new TypeScript version have been mitigated by:
* setting the `keyofStringsOnly` option until impacted code has been
future-proofed
* Restricting some joi-related generics
See the [release notes](https://www.typescriptlang.org/docs/handbook/release-notes/typescript-2-9.html) for details.
Some follow-up tasks should be:
* Update EUI to support the new `keyof` behaviour
* Update new platform TypeScript code to support new `keyof` behaviour
* Remove `keyofStringsOnly` setting
* Introduce @kbn/plugin-system
* Throw if plugin exposes a promise from 'start'
* TS updates
* rename
* Better error if missing plugin
* Api to add multiple specs at the same time
* isPromise prettier-ified
* Rename 'plugin' to 'system'
* Metadata + some cleanups
* Make it possible to type system metadata
* Throw if stop is async
* Add tests for System class