AesonException: Invalid flag name

[mrkkrp]

I wanted to try brittany, but stack said "no":

~/.stack $ stack install brittany-0.9.0.0 --resolver=nightly-2017-12-09
Downloaded nightly-2017-12-09 build plan.
AesonException "Error in $.packages.cassava.constraints.flags['bytestring--lt-0_10_4']: Invalid flag name: \"bytestring--lt-0_10_4\""
~/.stack $ stack --version
Version 1.5.1, Git revision 600c1f01435a10d127938709556c1682ecfd694e (4861 commits) x86_64 hpack-0.17.1

P.S. I'm forced to use 1.5.1, because 1.6.1 is not fully functional #3630.

[tfausak]

haskell-hvr/cassava#155 strikes again!

[decentral1se]

Sorry you got hit by this @mrkkrp. As you seem to know, this has been fixed in 1.6.1 and an upgrade is the answer to this problem. Hopefully #3630 can be resolved soon (I left a comment!). I'm not sure we get any value from leaving this issue open and I'm inclined to close it.

[kadoban]

Yeah, this is an unfortunate situation, but this particular bug has already been reported, found, fixed and released, so I don't think leaving this open is useful. Let's hope your other issue can be resolved quickly.

[giuliods]

I've got the same problem this days with the 1.6.5 stack version. I lurked for other solution but are too old or not resolved. Considering i can't upgrade stack what i need to do:

% stack exec -- yesod devel
Downloading lts-10.6 build plan ...
Downloaded lts-10.6 build plan.
AesonException "Error in $.packages.cassava.constraints.flags['bytestring--lt-0_10_4']: Invalid flag name: \"bytestring--lt-0_10_4\""
Type help for available commands. Press enter to force a rebuild.
quit
Yesod devel server. Enter 'quit' or hit Ctrl-C to quit.
Application can be accessed at:
http://localhost:3000
https://localhost:3443
If you wish to test https capabilities, you should set the following variable:
  export APPROOT=https://localhost:3443

% stack --version
Version 1.6.5, Git revision 24ab0d6ff07f28276e082c3ce74dfdeb1a2ca9e9 (5514 commits) x86_64 hpack-0.20.0

[tfausak]

Oh no, it's back!

I was not able to reproduce this problem with Stack 1.6.5 and LTS 10.6. I am not very familiar with yesod devel, but I'm guessing it shells out to stack. It's possible that the path is pointing to a different, older version of Stack. A quick peek at the code doesn't reveal anything obviously broken.

What does stack exec -- stack --version output?

[giuliods]

Nevermind, I resolved removing and reinstalling stack, removing .stack folder. Sorry for any concerns

[mgsloan]

Glad the workaround was effective for you!

🌿 🐛

[adhuliya]

FYI.
The error re-occurred for me, when I installed haskell-stack package form Ubuntu 18.04's updated repositories,

$ stack install hindent stylish-haskell
Writing implicit global project config file to: /home/codeman/.stack/global-project/stack.yaml
Note: You can change the snapshot via the resolver field there.
Using latest snapshot resolver: lts-12.10
Downloaded lts-12.10 build plan.    
AesonException "Error in $.packages.cassava.constraints.flags['bytestring--lt-0_10_4']: Invalid flag name: \"bytestring--lt-0_10_4\""

$ stack install hindent stylish-haskell
Downloaded lts-12.10 build plan.    
AesonException "Error in $.packages.cassava.constraints.flags['bytestring--lt-0_10_4']: Invalid flag name: \"bytestring--lt-0_10_4\""

However, after uninstalling haskell-stack and installing it with the command below, it worked.

curl -sSL https://get.haskellstack.org/ | sh

[JamesMcMahon]

Ubuntu 18.04 is using 1.5.1-1, which may have been affected by this bug.