AesonException "Error in $['system-info']: key \"os\" not present"


stack install pandoc
Downloaded lts-14.20 build plan.
AesonException “Error in $[‘system-info’]: key “os” not present”

What is this Exception telling me? Is pandoc installed? Or is there a system error?


I ran into this one some time ago but I don’t recall how I fixed it. But in general Stack sometimes breaks and deleting your “~/.stack” or “.stack-work” folders might help get it unstuck.


Well the ~/.stack is still there a ./stack-work I don’t have that


@Crojav what version of Stack are you using? This looks like Stack 1.x and with LTS-14 stackage snapshots we trimmed a bit getting rid of some details which are either were not used anymore or not used in Stack 2.


$ stack --version
Version 2.1.3, Git revision 636e3a759d51127df2b62f90772def126cdf6d1f (7735 commits) x86_64 hpack-0.31.2
$ ghci
GHCi, version 8.0.2: :? for help
Prelude> import Text.Pandoc
Prelude Text.Pandoc>


I see y 1.5.1 was mentioned in Started with Haskell - And what did I find? and the error above looks like something from that version. With Stack 2 you shouldn’t have this. BTW posting full verbose Stack log (you could set it with -v) could be very helpful.