Improve hover test_tooltip tests

[alexheretic]

After the discussion in #1151 this change:

• Splits test_tooltip into test_tooltip & test_tooltip_std. Only the latter will be ignored to avoid running upstream.
• Remove the --cfg=enabled_tooltip_tests stuff, the ignored test can be run with cargo test -- --ignored.
• Add string diff coloured output to tooltip tests.

Old/resolved

Windows Tests

I also tried to get to the bottom of the windows test failures. I managed to reproduce it on my local machine and traced the error to a panic without a backtrace from a rustfmt call:

rls/src/actions/hover.rs

Line 785 in bfa1371

let formatted = match rustfmt.format(object.clone(), config) {

error: unexpected close delimiter: `}`
 --> <stdin>:5:1
  |
5 | }
  | ^ unexpected close delimiter

This was quite painful to find but can be handled with std::panic::catch_unwind. I've added logging init to the tooltip tests. Hopefully we can get to the bottom of the still failing windows tests now the panic will not kill the test run.

[Xanewok]

The Windows CI test failure was caused by Racer - https://travis-ci.org/Xanewok/rls/jobs/465182472#L1336. Since it was changed some time ago to use byte offsets but still distinguished lines with lines() it led to a mismatch but can confirm that racer-rust/racer#1007 fixes the test now and autocompletion in Windows in general.

(However, right now toolstate is broken because of clippy so we'll need to wait for rust-lang/rust#56631 to land)

[alexheretic]

I've also added string diffs for tooltip test failures which seem pretty nice.

[Xanewok]

@aloucks @alexheretic
I wonder - could we just vendor our own copy of std-based source files and not depend on rust-src component? Or the idea is to have it act as integration test with the actual component that users have?

Being able to run entire test suite inside the Rust CI would definitely simplify things.

[alexheretic]

I'm not sure how that works, but being able to run the full test suite upstream would be great.

[Xanewok]

LGTM, I'd like to land this now modulo catch_unwind.

[Xanewok]

Thank you! Thankfully, for now Windows CI tests are fixed so I'll merge this and later update rustfmt asap when the upstream fix is merged.