The mixin `LspAnalysisServerTestMixin` contains a lot of helpers for interacting with the LSP server in tests and is used by both the in-process tests and the out-of-process integration tests.
We now have a third category of LSP tests that would benefit from many of these helpers (such as "getHover()") but are not talking to a native LSP server.
This change splits those helpers out into `LspRequestHelpersMixin` which contains only the request helpers without any code assuming a native LSP server, so they can be used by LSP-over-Legacy tests.
All code in `request_helpers_mixin.dart` was lifted directly from `server_abstract.dart` with no changes.
It also adds a test that error responses in LSP-over-Legacy are handled appropriately.
Change-Id: I847855a5314b5b04d700c6400b67e76e5f0d3402
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/313362
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Brian Wilkerson <brianwilkerson@google.com>
Danny Tuppeny
d718ab5f08