hls keeps crashing when path to log file is misconfigured

[jhrcek]

Subject of the issue

I was having some issues with HLS so I enabled logging for the haskell 1.1 vscode extension as follows:

After restarting vscode I started getting "The Haskell (backend) server crashed 5 times in the last 3 minutes. The server will not be restarted." errors.

It was quite a ride before I found the vscode log file with details 😆

$ cat .config/Code/logs/20201002T141614/exthost1/output_logging_20201002T141619/5-Haskell\ \(backend\).log
...
Consulting the cradle to get project GHC version...
Project GHC version: 8.8.3
haskell-language-server exe candidates: ["haskell-language-server-8.8.3","haskell-language-server-8.8","haskell-language-server"]
Launching haskell-language-server exe at:/home/jhrcek/.local/bin/haskell-language-server-8.8.3
haskell-language-server version: 0.4.0.0 (GHC: 8.8.3) (PATH: /home/jhrcek/.local/bin/haskell-language-server-8.8.3) (GIT hash: 5729c2ea119e9d48c136cc75c377d41fec811dde)
haskell-language-server-8.8.3: ~/hls.log: openFile: does not exist (No such file or directory)
haskell-language-server-wrapper: callProcess: /home/jhrcek/.local/bin/haskell-language-server-8.8.3 "--lsp" "-d" "-l" "~/hls.log" (exit 1): failed
[Info  - 2:16:20 PM] Connection to server got closed. Server will restart.

Your environment

• Output of haskell-language-server --probe-tools or haskell-language-server-wrapper --probe-tools
  haskell-language-server version: 0.4.0.0 (GHC: 8.8.3) (PATH: /home/jhrcek/.local/bin/haskell-language-server) (GIT hash: 5729c2e)
  Tool versions found on the $PATH
  cabal: 3.2.0.0
  stack: 2.3.3
  ghc: 8.8.3

• Which lsp-client do you use
  vscode

Steps to reproduce

In vscode, enter haskell extension settings and type "~/hls.log" as the file log file path
Restart vscode

Expected behaviour

Hls should start fine, maybe with logging disabled, but should definitely not crash.

Actual behaviour

The hls keeps crashing

Include debug information

Execute in the root of your project the command haskell-language-server --debug . and paste the logs here:

Debug output:

<paste your logs here>

Paste the logs from the lsp-client, e.g. for VS Code

LSP logs:

<paste your logs here>

[jhrcek]

The exception seems to be coming from here:
https://github.com/alanz/haskell-lsp/blob/ebd1d79762651bdeddb1928a91527c1429e62320/src/Language/Haskell/LSP/Core.hs#L1049

[jneira]

Afaiu the fix is merged in haskell-lsp but in the incoming 1.0.0.0 release

[justchilling]

This crashed-5-times-in-3-minutes is not a problem with the Haskell server, but with VS code itself. Though I don't know why this is happening. redhat-developer/vscode-java#743

[jneira]

afaik the client only tries to restart the server 5 times, whatever the reason caused the server crash, so the problem would be in the server

btw lsp-1.0 is being used in master so the fix should be included too