stack resolver lts-10.0 error: AesonException

[rimbaudcode]

When I start a new project, I get an AesonException:

$ stack new hello
Downloading template "new-template" to create project "hello" in hello/ ...
Looking for .cabal or package.yaml files to use to init the project.
Using cabal packages:
- hello/hello.cabal

Selecting the best among 12 snapshots...

Downloaded lts-10.0 build plan.
AesonException "Error in $.packages.cassava.constraints.flags: failed to parse field packages: failed to parse field constraints: failed to parse field flags: Invalid flag name: \"bytestring--lt-0_10_4\""

I'm using:

• stack Version 1.2.0 x86_64 hpack-0.14.0
• stack installed using Mac's homebrew
• ghc version 8.2.2
• macOS High Sierra 10.13.2 (17C88)

Cheers!

[kadoban]

Thanks for the report.

This is actually due to using an old version of stack. 1.2.0 is a few versions back. You'll have to upgrade unfortunately. stack upgrade is usually the easiest way.

[decentral1se]

Should we add a warning for this issue? A lot of tickets are being raised. A warning for < 1.6?

[rimbaudcode]

Great! Upgrading stack fixed the problem. I'm now running Version 1.6.1.1 x86_64 hpack-0.20.0 and the AesonException is gone.

However, I should point out that, before opening the current issue (#3686), I tried first stack update, with no change. Then, I uninstalled stack (and related files) and installed stack back, with no change either:

$ brew uninstall stack
$ trash ~/.stack ~/.cabal ~/.ghc
$ brew update && brew upgrade && brew cleanup && brew prune
$ brew install stack
$ stack new hello
Downloading template "new-template" to create project "hello" in hello/ ...
Looking for .cabal or package.yaml files to use to init the project.
Using cabal packages:
- hello/hello.cabal

Selecting the best among 12 snapshots...

Downloaded lts-10.0 build plan.
AesonException "Error in $.packages.cassava.constraints.flags: failed to parse field packages: failed to parse field constraints: failed to parse field flags: Invalid flag name: \"bytestring--lt-0_10_4\""

Maybe, the problem is due to an old version being of stack served by homebrew.

[decentral1se]

Yep - brew probably puts it in /usr/bin and stack puts executables in ~/.local/bin. A stack upgrade should have warned about not having ~/.local/bin on your $PATH if that was the case - otherwise, I think the original executable would take precedence?

[rimbaudcode]

I think you're right. Homebrew puts stuff in /usr/local/bin (https://docs.brew.sh/FAQ.html). In my $PATH, that dir is before stack's ~/.local/bin. So the original executable was being called. However, stack upgrade, and not a path change, fixed the AesonException. Maybe upgrading also solves other related issues?

[mgsloan]

Sounds like the overall issue here is resolved, so closing.

I'm not sure if 1.2.0 was recent enough, but at some point a warning was added to upgrade in the case that the destination location is not on your PATH.