Prelude.head: empty list makes hls unusable until restart #1618
Description
Your environment
Output of haskell-language-server --probe-tools or haskell-language-server-wrapper --probe-tools:
~/work-repo $ haskell-language-server --probe-tools
haskell-language-server version: 1.0.0.0 (GHC: 8.10.4) (PATH: /nix/store/1ngys7bwknlk8mixh5x3cxzxpnzn83ya-haskell-language-server-1.0.0.0/bin/haskell-language-server)
Tool versions found on the $PATH
cabal: 3.0.0.0
stack: 2.5.1.1
ghc: 8.10.4Which lsp-client do you use:
lsp-mode in emacs
Describe your project (alternative: link to the project):
n/a
Steps to reproduce
I'm not quite sure.
Expected behaviour
HLS should not die with a Prelude.head empty list error or at least report an error with call stack information
Actual behaviour
HLS seems "stuck" until restart
Include debug information
Execute in the root of your project the command haskell-language-server --debug . and paste the logs here:
I don't have time to take out information that I might be unable to share right now.
Debug output:
<paste your logs here>
Paste the logs from the lsp-client, e.g. for VS Code
LSP logs:
Found "/home/cody/work-proj/hie.yaml" for "/home/cody/work-proj/a"
Module "/home/cody/work-proj/a" is loaded by Cradle: Cradle {cradleRootDir = "/home/cody/work-proj", cradleOptsProg = CradleAction: Stack}
Run entered for haskell-language-server-wrapper(haskell-language-server-wrapper) Version 1.0.0.0 x86_64 ghc-8.10.4
Current directory: /home/cody/work-proj
Operating system: linux
Arguments: ["--lsp","-d","-l","/tmp/hls.log"]
Cradle directory: /home/cody/work-proj
Cradle type: Stack
Tool versions found on the $PATH
cabal: 3.0.0.0
stack: 2.5.1.1
ghc: 8.10.4
Consulting the cradle to get project GHC version...
Project GHC version: 8.10.4
haskell-language-server exe candidates: ["haskell-language-server-8.10.4","haskell-language-server-8.10","haskell-language-server"]
Launching haskell-language-server exe at:/run/current-system/sw/bin/haskell-language-server-8.10.4
haskell-language-server version: 1.0.0.0 (GHC: 8.10.4) (PATH: /nix/store/1ngys7bwknlk8mixh5x3cxzxpnzn83ya-haskell-language-server-1.0.0.0/bin/haskell-language-server)
Starting (haskell-language-server)LSP server...
with arguments: LspArguments {argLSP = True, argsCwd = Nothing, argFiles = [], argsShakeProfiling = Nothing, argsTesting = False, argsExamplePlugin = False, argsDebugOn = True, argsLogFile = Just "/tmp/hls.log", argsThreads = 0, argsProjectGhcVersion = False}
with plugins: [PluginId "brittany",PluginId "class",PluginId "eval",PluginId "floskell",PluginId "fourmolu",PluginId "ghcide-code-actions",PluginId "ghcide-completions",PluginId "ghcide-hover-and-symbols",PluginId "ghcide-type-lenses",PluginId "haddockComments",PluginId "hlint",PluginId "importLens",PluginId "moduleName",PluginId "ormolu",PluginId "pragmas",PluginId "retrie",PluginId "splice",PluginId "stylish-haskell",PluginId "tactic"]
in directory: /home/cody/work-proj
If you are seeing this in a terminal, you probably should have run ghcide WITHOUT the --lsp option!
Starting LSP server...
If you are seeing this in a terminal, you probably should have run ghcide WITHOUT the --lsp option!
Started LSP server in 0.00s
setInitialDynFlags cradle: Cradle {cradleRootDir = "/home/cody/work-proj", cradleOptsProg = CradleAction: Stack}
Output from setting up the cradle Cradle {cradleRootDir = "/home/cody/work-proj", cradleOptsProg = CradleAction: Stack}
> work-proj> configure (lib)
> Configuring work-proj-9003...
> work-proj> initial-build-steps (lib)
> Configuring GHCi with the following packages: work-proj
> /home/cody/work-proj/.stack-work/install/x86_64-linux-nix/bf73507d5ab7d23ffbc635ca9a779c93abe2b07d289a0605721872c193f83a77/8.10.4/pkgdb:/home/cody/.stack/snapshots/x86_64-linux-nix/bf73507d5ab7d23ffbc635ca9a779c93abe2b07d289a0605721872c193f83a77/8.10.4/pkgdb:/nix/store/26zbw2cg6w0ih8gr5ab8vh670mccrd3v-ghc-8.10.4/lib/ghc-8.10.4/package.conf.d
haskell-language-server-8.10.4: Prelude.head: empty list
What is /home/cody/work-proj/a? ls shows me file not found. Is that something synthetic hls adds?