How to fix hdevtools - "GHC_PACKAGE_PATH is incompatible.." error

Question

I'm a haskell beginner, I use the advent of code as learning examples. When setting up for this year I reinstalled stack (on a new machine, however copied most dotfiles over) and was starting from my last years notes and was not able to get hdevtools working again.

I have set up a new project with stack new advent2019 . In case it matters stack build on the "empty" project seems to take several minutes - seems much longer than last year. I install hdevtools with stack build hdevtools .

When I run stack exec hdevtools -- check src/Lib.hs I get following error:

Cabal error: hdevtools: Use of GHC's environment variable GHC_PACKAGE_PATH is incompatible
with Cabal. Use the flag --package-db to specify a package database (it can be
used multiple times).

So far I tried:

• I checked my shell and did an rg --no-ignore over my home directory to confirm GHC_PACKAGE_PATH is not set by me. Also over the project directory.
• I was not able to figure out how to use the mentioned --package-db flag - putting it after hdevtools I get an unknown flag error, putting it to stack I get an invalid option .
• stack exec --no-ghc-package-path hdevtools -- check src/Lib.hs - mentioned here
• I deleted all possible related files: ~/.local/bin/hdevtools , everything from ~/.stack , all ~/.ghc* .

None helped with the error.

I suppose I overlooked something obvious - however can you help point it out?

For completeness:

• on OS X, 10.15.1
• stack --version : Version 1.9.3, Git revision 40cf7b37526b86d1676da82167ea8758a854953b (6211 commits) x86_64 hpack-0.31.1
• stack ghc -- --version : The Glorious Glasgow Haskell Compilation System, version 8.6.5
• stack path :

stack-root: /Users/me/.stack
project-root: /Users/me/Code/advent2019
config-location: /Users/me/Code/advent2019/stack.yaml
bin-path: /Users/me/.stack/snapshots/x86_64-osx/lts-14.16/8.6.5/bin:/Users/me/.stack/compiler-tools/x86_64-osx/ghc-8.6.5/bin:/Users/me/.stack/programs/x86_64-osx/ghc-8.6.5/bin:/usr/local/texlive/2018basic/bin/x86_64-darwin:/Users/me/.local/bin/:/Users/me/.gem/bin:/Users/me/.yarn/bin:/Users/me/Library/Python/3.7/bin/:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin:/opt/X11/bin:/Library/Frameworks/Mono.framework/Versions/Current/Commands:/Library/TeX/texbin:.:/Applications/Wireshark.app/Contents/MacOS
programs: /Users/me/.stack/programs/x86_64-osx
compiler-exe: /Users/me/.stack/programs/x86_64-osx/ghc-8.6.5/bin/ghc
compiler-bin: /Users/me/.stack/programs/x86_64-osx/ghc-8.6.5/bin
compiler-tools-bin: /Users/me/.stack/compiler-tools/x86_64-osx/ghc-8.6.5/bin
local-bin: /Users/me/.local/bin
extra-include-dirs: 
extra-library-dirs: 
snapshot-pkg-db: /Users/me/.stack/snapshots/x86_64-osx/lts-14.16/8.6.5/pkgdb
local-pkg-db: /Users/me/Code/advent2019/.stack-work/install/x86_64-osx/lts-14.16/8.6.5/pkgdb
global-pkg-db: /Users/me/.stack/programs/x86_64-osx/ghc-8.6.5/lib/ghc-8.6.5/package.conf.d
ghc-package-path: /Users/me/Code/advent2019/.stack-work/install/x86_64-osx/lts-14.16/8.6.5/pkgdb:/Users/me/.stack/snapshots/x86_64-osx/lts-14.16/8.6.5/pkgdb:/Users/me/.stack/programs/x86_64-osx/ghc-8.6.5/lib/ghc-8.6.5/package.conf.d
snapshot-install-root: /Users/me/.stack/snapshots/x86_64-osx/lts-14.16/8.6.5
local-install-root: /Users/me/Code/advent2019/.stack-work/install/x86_64-osx/lts-14.16/8.6.5
snapshot-doc-root: /Users/me/.stack/snapshots/x86_64-osx/lts-14.16/8.6.5/doc
local-doc-root: /Users/me/Code/advent2019/.stack-work/install/x86_64-osx/lts-14.16/8.6.5/doc
dist-dir: .stack-work/dist/x86_64-osx/Cabal-2.4.0.1
/Users/me/Code/advent2019/.stack-work/install/x86_64-osx/lts-14.16/8.6.5/hpc
local-bin-path: /Users/me/.local/bin
ghc-paths: /Users/me/.stack/programs/x86_64-osx

Answer 1

The --no-ghc-package-path solution should have worked. However, you can just run hdevtools outside of Stack. On a Linux machine, if I run the following set of commands exactly:

$ stack new advent2019
$ cd advent2019
$ stack build
$ stack install hdevtools
$ hdevtools check src/Lib.hs

then hdevtools starts without error and runs in the background.

If your shell can't find hdevtools , it may be that ~/.local/bin is not in your path, so add it or try this instead:

$ ~/.local/bin/hdevtools check src/Lib.hs

Answer 2

Turns out I overlooked the .cabal directory in my purge. Though still had to also wipe .stack before installing hdevtools . Also had to build test separately so I would get dependency errors.

I don't think this is a solution for someone who uses haskell productively. Reminds me of my Windows 95 days where support told you to format and reinstall for every issue.