Attempt to fix the hls eval plugin test suite

[pepeiborra]

The test suite often fails with interactive eval errors like the one below:

GHC.ByteCode.Linker.lookupCE
During interactive linking, GHCi couldn't find the following symbol:
  interactive_Ghci1_evalPrint_closure

What does this error mean?

The GHC Session contains a mutable interactive context. During the Evaluate command, we first install a special "evalPrint" closure and then kick off the evaluation. These two steps are not atomic, and I think the error above means that the interactive context has been mutated in between those two steps.

What actions can mutate this interactive context? I'm not sure.

Who is mutating the GHC session? Since the GHC session is shared across the entire component, it could be any other build target.

But most tests only work with one module. Sure, but every test in this test suite reuses the test.cabal project with >20 modules. ghcide typechecks all the project modules at startup, and I don't think the tests wait for this initial typechecking to complete.

Result: the tests run the Eval command concurrently with the initial typechecking.

This PR disables the initial typechecking in this test suite, with the hope that the test suite will become less flaky.

[santiweight]

A heads up - I don't see any note of this in your commit message... I normally get this error when I click the refresh/evaluate code lenses and then click another while the initial code lens is still processing. Perhaps this is due to some concurrency?

[pepeiborra]

A heads up - I don't see any note of this in your commit message... I normally get this error when I click the refresh/evaluate code lenses and then click another while the initial code lens is still processing. Perhaps this is due to some concurrency?

It is mentioned in the PR description:

Result: the tests run the Eval command concurrently with the initial typechecking.

While this PR won't fix that issue in general, only in the testsuite, a recently landed PR should help: #2295

[pepeiborra]

Superseded by #2302 and #2303