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

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1

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?

2

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.

3

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

4

@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.

5

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

6

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.

7

I got the same exception
AesonException "Error in $['system-info']: key \"os\" not present"
upon trying to run stack test.

stack --version
Version 1.5.1 x86_64

So from what you say I should get stack 2 but being somehow new to Haskell and GHCI I’m not sure how to do this. Anyone could link me to a step by step process?

I tried :
sudo apt-get update && sudo apt-get install stack -y
and got
E: Unable to locate package stack

8

Try running stack upgrade

9

Cheers gilmi, it worked fine.

Just in case others come across the same issue, here’s the step-by-step:

$ stack upgrade(as advised)
$New stack executable available at somePath
$ cd ~/.somePath
$ stack init

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10

You probably don’t want to cd into ~/.somePath to run stack init. just make sure it is in your path and work elsewhere.

1 Like
11

Okay, thanks for the information. I just ran the init from there and then shifted back to my working dir.
So i should have initialized the stack directly from my working dir?

12

Stack init is used when you want use stack on an already existing cabal project. If you want to create a new project (from anywhere on your machine, I like to have my haskell projects at ~/code/haskell) you can use stack new instead.

See the user guide: https://docs.haskellstack.org/en/stable/GUIDE/