stack exec -- yesod devel

[legrostdg]

Not sure if the issue is in yesod-bin or in stack, but after building a yesod based project and installing yesod-bin with stack, I can't run "yesod devel":

$ stack exec -- yesod devel
Yesod devel server. Press ENTER to quit
Application can be accessed at:

http://127.0.0.1:3000
https://127.0.0.1:3443
If you wish to test https capabilities, you should set the following variable:
  export APPROOT=https://127.0.0.1:3443

cabal: 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).

[snoyberg]

It's a problem in Cabal, in that it won't recognize the GHC_PACKAGE_PATH environment variable, and yesod devel which uses cabal. The proper solution will be to move yesod devel off of cabal, which will hopefully be part of the current GSoC project to move over to ide-backend. In the meanwhile, unfortunately yesod devel is not compatible with stack, at least not directly as we'd like.

[legrostdg]

Is there a workaround? I noticed the same problem with propellor https://propellor.branchable.com, which I guess won't be updated to ide-backend...

haskell/cabal#2270 may be a fix?

[snoyberg]

It depends on what you mean by "workaround." You can use env to disable the GHC_PACKAGE_PATH environment variable (and we can provide a flag to exec to automate that). But in the case of yesod devel, that will mean you end up not having the packages in scope.

Another possibility would be to tweak yesod devel to parse GHC_PACKAGE_PATH, turn it into command line parameters for cabal, and unset the environment variable. Which presumably is what cabal should be doing anyway. propellor could do the same thing.

[legrostdg]

closed by a7cccf2
Thanks!

[snoyberg]

You're fast, the blog post isn't even out yet!

[geraldus]

Oh, cool, thanks! Now I can use stack (:

[legrostdg]

@snoyberg you are the fast one!

I just updated my yesod git clone by chance and noticed the latest commit :).

[tfiala]

I seem to be hitting this issue with 'stack exec -- yesod test':

stack exec -- yesod test
cabal: 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).

I've got stack exec -- yesod devel working just fine. Is this likely another instance of the problem solved here for the devel command?

[snoyberg]

I wouldn't bother using yesod test with stack, just use stack test.

[tfiala]

Ah, thanks! I am new to both Haskell and stack, and didn't even know 'stack test' was an option. I'm just getting started with the 2nd ed book and it pointed to stack. (And stack test did work :-) ).