How to debug hie problems?

[jwiegley]

I'm having some difficulties getting haskell-ide-engine working under Emacs with my Nix configuration. Right now I'm facing this:

hie: <command line>: cannot satisfy -package-id aeson-1.2.4.0-G9AwmJGyHa062BMlqjD9fS
    (use -v for more information)

However, as far as I can tell, this is available in my environment, and cabal is building with this version of the library.

Is there a way to run hie so that I can try to track down where this is coming from? I'm not even sure yet how this is being triggered, since if I just run "hie" on the command-line, it doesn't report any errors, but neither do I know how to simulate whatever Emacs does when I open a Haskell file.

I'm asking here because I don't know what to do next, and I'd love to start using HIE for development. Thanks!

[lukel97]

There are a bunch of flags you can pass to HIE to get some extra information

• --debug will output extra information to stderr
• --vomit will output extra information from ghc-mod to stderr
• -l /log/file will specify a directory to output logs such about requests received and responses received to a certain directory.

Is the project that you're running HIE on a stack project? If so make sure there aren't any dist or new-dist or cabal.project.local or .ghc-environment files lying around that might trick it into using cabal. I also found that I got that error when the version of HIE doesn't match the resolver that the project uses, i.e. if you're using GHC 8.2.2 then your client should run hie-8.2.2 that was installed via make build

[alanz]

@jwiegley, the best approach for use under nix is to look at https://github.com/domenkozar/hie-nix

[jwiegley]

Yes, that's what I've been using.

[alanz]

Great. Does this mean we can close this issue?

[alanz]

Unless you want to make a PR on the docs, and then close it ... :)

[jwiegley]

I guess the question is: is there a way from the command-line to poke HIE to do what it's going to do when I say, try to lookup an identifier in a file. For example, it's much easier to diagnose hdevtools problem, because I can run hdevtools check ... at the command-line to at least take Emacs out of the picture until the CLI is working. But with HIE, it seems that once I run it I enter into some kind of event loop, but I don't know what events to send it. There are too many layers between Emacs and HIE for me to understand what's triggering the error that I see.

[alanz]

This is unfortunately a byproduct on focusing on LSP, and deprecating the other methods (which were always pretty iffy anyway, especially the console).

Hopefully the GSOC work @Bubba is doing will make this easier in future.

[jwiegley]

Do you know of any CLI that can fabricate the kinds of events Emacs is probably sending?

[alanz]

Not at the moment.

But as I said, most likely option is going to be https://github.com/Bubba/haskell-lsp-test

[cah6]

@jwiegley I ran into the same thing in my local setup (with Nix). I finally found https://github.com/NixOS/nixpkgs/pull/46453, though setting those env variables manually still didn't fix my editor integration. Maybe the other changes in that PR fix it, or maybe it's something else...still investigating.

[alanz]

I guess we should update the README for this, then close it.

[Anrock]

I'm willing to tackle some issue on holidays, but i have to idea what proper development process on hie is. For some trivial issues in past i used printf-style debugging and it was barely enough, i guess i need a proper debugger and a way to emulate events and checkout what is going on.

Is there any blog posts \ articles \ gists \ notes \ whatever about it? @alanz @bubba @wz1000 what are your workflows for hie development?

[alanz]

I am a great fan of printf-style debugging, although I generally use logm and then look at what is happening in /tmp/hie.log.

You can also have a look at how the functional tests are run, they also generate logs, and you can focus them using the hspec --match command line parameter.

I have a file test.sh in my root directory, which looks like this

#!/bin/sh

# stack test haskell-ide-engine:func-test --test-arguments "--failure-report .hspec-failures --rerun"
stack test haskell-ide-engine:func-test --test-arguments "--match \"completes ghc options pragma values\""

[wz1000]

You might also see if you can get https://microsoft.github.io/language-server-protocol/inspector/ to work with hie.

Generally, even I use printf debugging with logm etc. Also, --vomit is a good option to have enabled to debug ghc/ghc-mod issues.

For emulating events, you can look at @bubba's lsp-test stuff, with examples in test/functional

[wz1000]

tail -f hie.log | grep -B n "something" is also a great way to filter out specific stuff from the log

[lukel97]

@Anrock if you're using VS Code to develop with HIE, a nice workflow is to print to stderr which then shows up in the output window

[jhenahan]

If anyone's still running into this, I managed to get things working the way I expected by adding direnv-update-environment to my language mode hook after setting up all my LSP related hooks. That is, I have

(use-package haskell-mode
  ...
  :hook ((haskell-mode . direnv-update-environment))
  ...)

where my lang-specific configs are loaded later than my LSP config. This seems to put the direnv hook ahead of the LSP hook, so it does the right thing.