My Nix project's cabal file defines a flag but leaves it disabled by default:
flag with-examples
description: Include examples and their dependencies
default: False
But when I run haskell-language-server in the nix-shell, it says:
Hidden: no
Range: 1:1-2:1
Source: cradle
Severity: DsError
Message:
Error when calling cabal exec -v0 -- ghc --print-libdir
cabal: Could not resolve dependencies:
[__0] trying: ema-0.7.2.0 (user goal)
[__1] rejecting: ema:-with-examples (constraint from config file, command line
flag, or user target requires opposite flag selection)
[__1] trying: ema:+with-examples
[__2] unknown package: fsnotify (dependency of ema +with-examples)
[__2] fail (backjumping, conflict set: ema, fsnotify, ema:with-examples)
After searching the rest of the dependency tree exhaustively, these were the
goals I've had most trouble fulfilling: ema, ema:with-examples, fsnotify
The error goes away after making the flag True by default, but this is a clearly undesired behavior. Is there a way to fix this behavior of HLS?
I tried adding a cabal.project file with flags: +with-examples but that makes no difference.
To reproduce this error:
git clone https://github.com/EmaApps/ema.git -b multisite
cd multisite && nix develop
nvim ema.cabal ## Make both the flags default: False
haskell-language-server
(edited to clarify this is unique to Nix)