Crash/incorrect error message on circular dependency

[cgeorgii]

Description

Sometimes during a refactor I might accidentally introduce a module import that causes a circular/cyclical dependency. ghcid might then fail in one of two ways:

• It crashes; or
• It reports All good (X modules, at 19:12:42), where X is a number lower than the number of actual modules in the project, i.e. not all modules were typechecked.

I'm not sure how to trigger one or the other, they seem to happen randomly/under unclear circumstances.

Since HLS manages to identify the cycle and report correctly, I believe this is a bug in ghcid.

How to reproduce

Create two modules A and B and import them from one another:

-- src/A.hs
module A where
import B

-- src/B.hs
module B where
import A

Run ghcid:

$ ghcid --command "cabal repl component-name"

Witness the issue.

Version information

❯ ghcid -V
Auto reloading GHCi daemon v0.8.7

[ffaf1]

Indeed I get No files loaded, nothing to wait for. Fix the last error and restart. and ghcid quits.

It would be prettier if ghcid did not exit, it is a bit of a nuisance having to restart it.

[smelc]

Reported as a potential good issue for bench time, cc @tek @yannham