ghc-modi throws error when checking type info

[shengc]

Killing ghc-modi due to process failure.<br/><br/>You can restart it using <b>Tools &gt; Restart ghc-modi</b><br/><br/>Executing ghc-modi command 'type ****************** 9 2' failed with error: Failed to write command to ghc-modi: ghc-mod: cabal: readCreateProcess: runInteractiveProcess: exec: does not exist (No such file or directory)

What I don't understand is why it still tried to look for cabal since I have configured the project to use stack. Besides I ran the type command in a ghc-modi session opened by myself, and the output was sane,

9 1 9 50 "Maybe Integer"
OK

[shengc]

Does the plugin support the latest idea (2016.1.1) ? There are couple of exceptions like below in the event log, though I have configured both the compiler and tools in preference.

ghc
        Failed to create process for command: "" --numeric-version
        Caused by: com.intellij.execution.ExecutionException: Executable is not specified
cabal
        Failed to create process for command: "" --numeric-version
        Caused by: com.intellij.execution.ExecutionException: Executable is not specified

I included the ghc in the PATH, now the event log shows another error,

ghc
        Nonzero exit status (1) from command: /usr/local/bin/stack --stack-yaml /Users/shengc/Documents/workspace/haskell/hpffp/stack.yaml ghc -- --numeric-version
        Process stderr: After installing Cabal, the package id couldn't be found (via ghc-pkg describe Cabal). This shouldn't happen, please report as a bug
        Configure

the -- between ghc and --numeric-version caused the error message. But again, it should not check ghc or cabal since the compiler is using stack

[carymrobbins]

@shengc - Have you checked out the Haskell Tools Console? It might give you some additional information. Paste any info you see here (or in a gist if it's a lot).

HaskForce should be compatible with 2016.1.1, but I'll dig in tomorrow to see if I can reproduce your issue.

[carymrobbins]

Also, can you provide the version of ghc-mod that you are using?

[shengc]

@carymrobbins The output in the console is not so much different from what I just pasted, but anyway there you go,

list
check *******.hs
check *******.hs
Using working directory: ********
Starting ghc-modi process: /usr/local/bin/stack exec -- /Users/shengc/.local/bin/ghc-mod legacy-     interactive
type *******.hs 75 2
ghc-mod: cabal: readCreateProcess: runInteractiveProcess: exec: does not exist (No such file or directory)

I am using stack 1.0.4, ghc 7.10.3, and ghc-mod 5.5.0.0 on OS X 10.11.4

[shengc]

@carymrobbins I also noticed that if I Ctrl clicked (well, it was actually "Command clicked") on a function coming from Prelude or a dependency, the UI would completely freeze. I had to send SIGKILL to terminate idea and restarted.

[carymrobbins]

Sorry for the late delay!

The output in the console is not so much different from what I just pasted, but anyway there you go

One thing that stands out to me is the spacing in the legacy- and interactive. You may want to check your Haskell Tools configuration to ensure that the command line options are correct (should be legacy-interactive for ghc-modi).

I'd also run the following and post back to confirm the existence of the executable -

$ [ -f /Users/shengc/.local/bin/ghc-mod ] && echo exists || echo missing
$ [ -x /Users/shengc/.local/bin/ghc-mod ] && echo executable || echo not executable

I also noticed that if I Ctrl clicked (well, it was actually "Command clicked") on a function coming from Prelude or a dependency, the UI would completely freeze. I had to send SIGKILL to terminate idea and restarted.

If this happens, you could also run -

$ jps -l | grep intellij   
8143 com.intellij.idea.Main
$ jstack 8143 > stacktrace.txt

Then post the resulting stacktrace.txt to a gist and link to it. From there that should give some insight as to exactly what is causing the freeze. I'm thinking it's probably the parser.

[danielstory]

Just leaving a comment here because I spent several hours today pulling my hair out trying to make this work, and came across this thread in the process:

If you're getting the ghc-mod: cabal: readCreateProcess: runInteractiveProcess: exec: does not exist error on Mac OS X, one possible cause is that the stack executable is not in the PATH used by IDEA, since it's a GUI app. (This is almost certainly the case if you installed stack to /usr/local/bin or ~/.local/bin and haven't gone through extraordinary lengths to override the path used by OSX GUI apps.) If ghc-mod doesn't find the stack executable, it falls back to cabal as the build system, generating that error message.

To fix this, supply the --with-stack=/path/to/stack parameter to ghc-mod in Preferences -> Other Settings -> Haskell Tools.

@carymrobbins: It might be a good idea to have Haskforce supply the --with-stack or --with-cabal parameters automatically, since it knows which build system you're using and where the executable is located as part of its own setup process.

[jasoncorso]

@danielstory Although you have identified the problem (stack path on OS X), I could not get it to work by passing the --with-stack=/path/to/stack as a parameter to ghc-mod. I did however succeed by making a symlink from /usr/bin (an insecure hack, but confirmed the issue).

[carymrobbins]

Note that when when using stack, ghc-mod is executed in the context of stack, semantically -

% stack exec -- ghc-mod <args>

@DanielG - Should --with-stack work to solve this issue? It seems that it is working for some (@danielstory) but not others (@jasoncorso). I could update HaskForce to use this flag, but I'm not sure if that would actually solve the problem at the moment. Although, I seem to recall the possibility of ghc-mod using the STACK_EXE environment variable that stack provides.

In the interim, one possible workaround would be to use a script to take care of this.

stack-wrapper

#!/bin/bash

stack_path=/usr/local/bin/stack
stack_dir=$(basename "$("$stack_path" exec -- bash -c 'echo $STACK_EXE')")
export PATH=$PATH:$(basename "$stack_exe")
exec "$stack_path" "$@"

Then you could configure IntelliJ to use path/to/stack-wrapper instead of stack. It's a bit of a hack, but may help until we have found the right solution.

[DanielG]

Yes --with-stack should fix this if the problem is stack not being in PATH. The stack exec -- ghc-mod ... thing only works properly with >5.6 though where I added some code to check if STACK_EXE is set and actually exists.