在 package.yaml 中的哪里添加标志？

Question

I have a package.yaml file like:

name: ...
version: ...

...

flags:
  strict: ...
    description: ...
    ...

dependencies:
  ...

...

Mostly typical package.yaml file. And one of the dependencies uses a library (so it's a transitive dependency) which has flags (one of them is use-pkg-config flag).

How to turn on this flag? I tried:

pkg-config-dependencies: that-library

Also I tried to add a GHC option:

...
ghc-options:
  ...
  -fuse-pkg-config

and to add flags: section to library: , it seems it does not work because I see in the compilation console output:

......... -f-use-pkg-config ....

and not -fuse-pkg-config , so I suppose it does not work. How to add a flag for such dependency (it's transitive - I don't know it matters or not) in package.yaml ?

Answer 1

Flags can be specified in project-level configuration files, stack.yaml or cabal.project .

-- cabal.project
package my-dependency
  flag: +use-pkg-config

# stack.yaml
flags:
  my-dependency:
    use-pkg-config: true

Documentation:

• cabal https://cabal.readthedocs.io/en/stable/cabal-project.html#cfg-field-flags

• stack https://docs.haskellstack.org/en/stable/yaml_configuration/#flags