Nix Haskell Library Functions and `cabal2nix` Integration

environment is missing the dependencies necessary for compiling the benchmark component. `dontBenchmark drv` : Set `doBenchmark` to `false` for `drv`. `setBuildTargets drv list` : Sets the `buildTarget` argument for `drv` so that the targets specified in `list` are built. `doCoverage drv` : Sets the `doCoverage` argument to `true` for `drv`. `dontCoverage drv` : Sets the `doCoverage` argument to `false` for `drv`. `enableExecutableProfiling drv` : Sets the `enableExecutableProfiling` argument to `true` for `drv`. `disableExecutableProfiling drv` : Sets the `enableExecutableProfiling` argument to `false` for `drv`. `enableLibraryProfiling drv` : Sets the `enableLibraryProfiling` argument to `true` for `drv`. `disableLibraryProfiling drv` : Sets the `enableLibraryProfiling` argument to `false` for `drv`. `disableParallelBuilding drv` : Sets the `enableParallelBuilding` argument to `false` for `drv`. #### Library functions in the Haskell package sets {#haskell-package-set-lib-functions} Some library functions depend on packages from the Haskell package sets. Thus they are exposed from those instead of from `haskell.lib.compose` which can only access what is passed directly to it. When using the functions below, make sure that you are obtaining them from the same package set (`haskellPackages`, `haskell.packages.ghc944` etc.) as the packages you are working with or – even better – from the `self`/`final` fix point of your overlay to `haskellPackages`. Note: Some functions like `shellFor` that are not intended for overriding per se, are omitted in this section.  `cabalSdist { src, name ? ... }` : Generates the Cabal sdist tarball for `src`, suitable for uploading to Hackage. Contrary to `haskell.lib.compose.sdistTarball`, it uses `cabal-install` over `Setup.hs`, so it is usually faster: No build dependencies need to be downloaded, and we can skip compiling `Setup.hs`. `buildFromCabalSdist drv` : Build `drv`, but run its `src` attribute through `cabalSdist` first. Useful for catching files necessary for compilation that are missing from the sdist. `generateOptparseApplicativeCompletions list drv` : Generate and install shell completion files for the installed executables whose names are given via `list`. The executables need to be using `optparse-applicative` for [this to work][optparse-applicative-completions]. Note that this feature is automatically disabled when cross-compiling, since it requires executing the binaries in question. ## Import-from-Derivation helpers {#haskell-import-from-derivation} ### cabal2nix {#haskell-cabal2nix} [`cabal2nix`][cabal2nix] can generate Nix package definitions for arbitrary Haskell packages using [import from derivation][import-from-derivation]. `cabal2nix` will generate Nix expressions that look like this: ```nix # cabal get mtl-2.2.1 && cd mtl-2.2.1 && cabal2nix . { mkDerivation, base, lib, transformers, }: mkDerivation { pname = "mtl"; version = "2.2.1"; src = ./.; libraryHaskellDepends = [ base transformers ]; homepage = "http://github.com/ekmett/mtl"; description = "Monad classes, using functional dependencies"; license = lib.licenses.bsd3; } ``` This expression should be called with `haskellPackages.callPackage`, which will supply [`haskellPackages.mkDerivation`](#haskell-mkderivation) and the Haskell dependencies as arguments. `callCabal2nix name src args` : Create a package named `name` from the source derivation `src` using `cabal2nix`. `args` are extra arguments provided to `haskellPackages.callPackage`. `callCabal2nixWithOptions name src opts args` : Create a package named `name` from the source derivation `src` using `cabal2nix`. `opts` are extra options for calling `cabal2nix`. If `opts` is a string, it will be used as extra command line arguments for `cabal2nix`, e.g. `--subpath path/to/dir/containing/cabal-file`. Otherwise, `opts` should be an AttrSet which can contain the following attributes:

This chunk concludes the list of Nix Haskell helper functions, covering build controls like benchmarking, build targets, code coverage, profiling, and parallel building. It then introduces 'Library functions in the Haskell package sets,' including `cabalSdist` for efficient Cabal source distribution generation, `buildFromCabalSdist`, and `generateOptparseApplicativeCompletions` for shell completions. The document transitions to 'Import-from-Derivation helpers', detailing `cabal2nix`. It explains how `cabal2nix` generates Nix package definitions from Haskell projects, providing an output example. Finally, it describes `callCabal2nix` for creating packages from source with `cabal2nix` and additional `callPackage` arguments, along with `callCabal2nixWithOptions` for passing extra `cabal2nix` command-line or attribute set options.