flake-parts

`perSystem.haskellProjects.<name>.basePackages`

Which Haskell package set / compiler to use.

You can effectively select the GHC version here.

To get the appropriate value, run:

nix-env -f "<nixpkgs>" -qaP -A haskell.compiler

And then, use that in pkgs.haskell.packages.ghc<version>

Type: attribute set of raw value

Default: pkgs.haskellPackages

Example: "pkgs.haskell.packages.ghc924"

Declared by:

`perSystem.haskellProjects.<name>.debug`

Whether to enable verbose trace output from haskell-flake.

Useful for debugging.

Type: boolean

Default: false

Declared by:

`perSystem.haskellProjects.<name>.defaults.enable`

Whether to enable haskell-flake’s default settings for this project.

Type: boolean

Default: true

Declared by:

`perSystem.haskellProjects.<name>.defaults.packages`

Local packages scanned from projectRoot

Type: lazy attribute set of module

Default: If you have a cabal.project file (under projectRoot), those packages are automatically discovered. Otherwise, the top-level .cabal file is used to discover the only local package.

haskell-flake currently supports a limited range of syntax for cabal.project. Specifically it requires an explicit list of package directories under the “packages” option.

Declared by:

`perSystem.haskellProjects.<name>.defaults.devShell.tools`

Build tools always included in devShell

Type: function that evaluates to a(n) attribute set of (null or package)

Default: <function>

Declared by:

`perSystem.haskellProjects.<name>.defaults.projectModules.output`

A haskell-flake project module that exports the packages and settings options to the consuming flake. This enables the use of this flake’s Haskell package as a dependency, re-using its overrides.

Type: module

Default: a generated module

Declared by:

`perSystem.haskellProjects.<name>.defaults.settings.default`

Default settings for all packages in packages option.

Type: module

Default:

'' Speed up builds by disabling haddock and library profiling.

This uses local.toDefinedProject option to determine which packages to override. Thus, it applies to both local packages as well as transitively imported packags that are local to that flake (managed by haskell-flake). The goal being to use the same configuration consistently for all packages using haskell-flake. ''

Declared by:

haskell-flake/nix/modules/project/hls-check.nix, haskell-flake/nix/modules/project/devshell.nix

`perSystem.haskellProjects.<name>.devShell`

Development shell configuration

Type: submodule

Default: { }

Declared by:

`perSystem.haskellProjects.<name>.devShell.enable`

Whether to enable a development shell for the project.

Type: boolean

Default: true

Declared by:

`perSystem.haskellProjects.<name>.devShell.benchmark`

Whether to include benchmark dependencies in the development shell. The value of this option will set the corresponding doBenchmark flag in the shellFor derivation.

Type: boolean

Default: false

Declared by:

`perSystem.haskellProjects.<name>.devShell.extraLibraries`

Extra Haskell libraries available in the shell’s environment. These can be used in the shell’s runghc and ghci for instance.

The argument is the Haskell package set.

The return type is an attribute set for overridability and syntax, as only the values are used.

Type: function that evaluates to a(n) attribute set of (null or package)

Default: hp: { }

Example: hp: { inherit (hp) releaser; }

Declared by:

`perSystem.haskellProjects.<name>.devShell.hlsCheck`

A check to make sure that your IDE will work.

Type: submodule

Default: { }

Declared by:

`perSystem.haskellProjects.<name>.devShell.hlsCheck.enable`

Whether to enable a flake check to verify that HLS works.

This is equivalent to nix develop -i -c haskell-language-server.

Note that, HLS will try to access the network through Cabal (see https://github.com/haskell/haskell-language-server/issues/3128), therefore sandboxing must be disabled when evaluating this check.

Type: boolean

Default: false

Declared by:

`perSystem.haskellProjects.<name>.devShell.hlsCheck.drv`

The hlsCheck derivation generated for this project.

Type: package (read only)

Declared by:

`perSystem.haskellProjects.<name>.devShell.hoogle`

Whether to include Hoogle in the development shell. The value of this option will set the corresponding withHoogle flag in the shellFor derivation.

Type: boolean

Default: true

Declared by:

`perSystem.haskellProjects.<name>.devShell.mkShellArgs`

Extra arguments to pass to pkgs.mkShell.

Type: attribute set of raw value

Default: { }

Example:

''
  {
    shellHook = \'\'
      # Re-generate .cabal files so HLS will work (per hie.yaml)
      ''${pkgs.findutils}/bin/find -name package.yaml -exec hpack {} \;
    \'\';
  };
''

Declared by:

`perSystem.haskellProjects.<name>.devShell.tools`

Build tools for developing the Haskell project.

These tools are merged with the haskell-flake defaults defined in the defaults.devShell.tools option. Set the value to null to remove that default tool.

Type: function that evaluates to a(n) attribute set of (null or package)

Default: <function>

Declared by:

haskell-flake/nix/modules/project/hls-check.nix, haskell-flake/nix/modules/project/outputs.nix, haskell-flake/nix/modules/project/devshell.nix

`perSystem.haskellProjects.<name>.outputs`

The flake outputs generated for this project.

This is an internal option, not meant to be set by the user.

Type: submodule

Declared by:

`perSystem.haskellProjects.<name>.outputs.packages`

Package information for all local packages. Contains the following keys:

package: The Haskell package derivation
exes: Attrset of executables found in the .cabal file

Type: attribute set of (submodule) (read only)

Declared by:

`perSystem.haskellProjects.<name>.outputs.packages.<name>.package`

The local package derivation.

Type: package

Declared by:

`perSystem.haskellProjects.<name>.outputs.packages.<name>.exes`

Attrset of executables from .cabal file.

If the associated Haskell project has a separate bin output (cf. enableSeparateBinOutput), then this exe will refer only to the bin output.

NOTE: Evaluating up to this option will involve IFD.

Type: attribute set of (submodule)

Declared by:

`perSystem.haskellProjects.<name>.outputs.packages.<name>.exes.<name>.program`

A path to an executable or a derivation with meta.mainProgram.

Type: string or package convertible to it

Declared by:

`perSystem.haskellProjects.<name>.outputs.packages.<name>.exes.<name>.type`

A type tag for apps consumers.

Type: value “app” (singular enum)

Default: "app"

Declared by:

`perSystem.haskellProjects.<name>.outputs.apps`

Flake apps for each Cabal executable in the project.

Type: attribute set of (submodule) (read only)

Declared by:

`perSystem.haskellProjects.<name>.outputs.apps.<name>.program`

A path to an executable or a derivation with meta.mainProgram.

Type: string or package convertible to it

Declared by:

`perSystem.haskellProjects.<name>.outputs.apps.<name>.type`

A type tag for apps consumers.

Type: value “app” (singular enum)

Default: "app"

Declared by:

`perSystem.haskellProjects.<name>.outputs.checks`

The flake checks generated for this project.

Type: lazy attribute set of package (read only)

Declared by:

`perSystem.haskellProjects.<name>.outputs.devShell`

The development shell derivation generated for this project.

Type: package (read only)

Declared by:

`perSystem.haskellProjects.<name>.outputs.finalPackages`

The final Haskell package set including local packages and any overrides, on top of basePackages.

Type: attribute set of raw value (read only)

Declared by:

`perSystem.haskellProjects.<name>.projectFlakeName`

A descriptive name for the flake in which this project resides.

If unspecified, the Nix store path’s basename will be used.

Type: null or string

Default: null

Declared by:

`perSystem.haskellProjects.<name>.projectRoot`

Path to the root of the project directory.

Chaning this affects certain functionality, like where to look for the ‘cabal.project’ file.

Type: path

Default: "Top-level directory of the flake"

Declared by: