Nix-writers

Nix-writers are a way to write other programming languages inline in nix-code. They are like writeScript/writeScriptBin but for other languages.

Every writer has a ...Bin variant which can be used inside environment.systemPackages. Most of the writers take an attrributeset where one can add libraries.

These are declared in /pkgs/build-support/writers/scripts.nix.

Languages

bash

This is basically writeScript but with the shebang to bash already included.

pkgs.writers.writeBash "hello_world" ''
  echo 'hello world!'
''

dash

pkgs.writers.writeDash "hello_world" ''
  echo 'hello world!'
''

Haskell

writeHaskell "missiles" {
  libraries = [ pkgs.haskellPackages.acme-missiles ];
} ''
  import Acme.Missiles

  main = launchMissiles
''

JavaScript

writeJS "example" {
  libraries = [ pkgs.nodePackages.uglify-js ];
} ''
  var UglifyJS = require("uglify-js");
  var code = "function add(first, second) { return first + second; }";
  var result = UglifyJS.minify(code);
  console.log(result.code);
''

Perl

writePerl "example" {
  libraries = [ pkgs.perlPackages.boolean ];
} ''
  use boolean;
  print "Howdy!\n" if true;
''

Python2

writePython2 "test_python2" {
  deps = [ pkgs.python2Packages.enum ];
} ''
  from enum import Enum

  class Test(Enum):
      a = "success"

  print Test.a
''

Python3

writePython3 "test_python3" {
  libraries = [ pkgs.python3Packages.pyyaml ];
} ''
  import yaml

  y = yaml.load("""
    - test: success
  """)
  print(y[0]['test'])
''

To disable errors use 'flakeIgnore' like this:

writePython3 "test_python3" {
  libraries = [ pkgs.python3Packages.pyyaml ];
  flakeIgnore = [ "E265" "E225" ];
} ''
  import yaml

  y = yaml.load("""
    - test: success
  """)
  print(y[0]['test'])
''