termonad-4.4.0.0: .nix-helpers/nixpkgs.nix

# This file pins the version of nixpkgs to a known good version. The nixpkgs is
# imported with an overlay adding Termonad. It is imported from various other
# files.

{ # A path to nixpkgs.  This will be imported.  If null, use a known-working
  # nixpkgs version.
  nixpkgs ? null
, # Additional overlays to apply when importing nixpkgs.
  additionalOverlays ? []
, # String representing a GHC version to use.  Normally something like
  # "ghc865".  If null, then use a known-working GHC version.
  compiler ? null
, # Build all the examples bundled with termonad.  Normally this is only used
  # in CI for testing that the examples all still compile.
  buildExamples ? false
, # Enable SIXEL support in VTE.
  #
  # Setting this to true builds the VTE library with SIXEL enabled. Note that
  # this uses a special version of VTE that may still have issues.  This is
  # necessary because VTE doesn't yet support SIXEL by default in their release
  # versions. See https://github.com/cdepillabout/termonad/pull/221 and
  # https://github.com/cdepillabout/termonad/pull/219 for more information and
  # examples of what SIXEL looks like in Termonad.
  #
  # Also, see https://gitlab.gnome.org/GNOME/vte/-/issues/253 which seems to be
  # the upstream VTE issue for the SIXEL implementation.
  #
  # TODO: Remove this option when the upstream VTE releases officially support
  # SIXEL.
  enableSixelSupport ? false
, # This is only used for `termonadShell`.
  #
  # If this is `true`, Hoogle will also index the Termonad libraries,
  # however this will mean the environment will need to be rebuilt every
  # time the termonad source changes.
  indexTermonad ? false
, # Extra Haskell packages that will be visible by Termonad when it compiles
  # itself.  See ./termonad-with-packages.nix for an example of how to use
  # this.
  extraHaskellPackages ? null
}:

let
  flake-lock = builtins.fromJSON (builtins.readFile ../flake.lock);

  nixpkgsSrc =
    if isNull nixpkgs
      then
        builtins.fetchTarball {
          url = "https://github.com/NixOS/nixpkgs/archive/${flake-lock.nodes.nixpkgs.locked.rev}.tar.gz";
          sha256 = flake-lock.nodes.nixpkgs.locked.narHash;
        }
      else nixpkgs;

  haskellPackagesOverlays = import ./overlays.nix;

  # This overlay sets some of the options use we at development time. This
  # overlay is basically an easy way to pass options to `./overlays.nix`
  # without having to do it explicitly.
  termonadOptionsOverlay = self: super: {
    termonadCompilerVersion =
      if isNull compiler then super.termonadCompilerVersion else compiler;

    termonadBuildExamples = buildExamples;

    termonadIndexTermonad = indexTermonad;

    termonadExtraHaskellPackages =
      if isNull extraHaskellPackages then super.termonadExtraHaskellPackages else extraHaskellPackages;

    termonadEnableSixelSupport = enableSixelSupport;
  };

in

import nixpkgsSrc {
  overlays =
    haskellPackagesOverlays ++ [ termonadOptionsOverlay ] ++ additionalOverlays;
}