Create Haskell playground template

This commit is contained in:
Félix Baylac-Jacqué 2021-02-06 19:35:50 +01:00
commit 1dff0fd75b
Signed by: picnoir
GPG Key ID: EFD315F31848DBA4
8 changed files with 271 additions and 0 deletions

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CHANGELOG.md Normal file
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# Revision history for haskell-playground
## 0.1.0.0 -- YYYY-mm-dd
* First version. Released on an unsuspecting world.

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Main.hs Normal file
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module Main where
main :: IO ()
main = putStrLn "Hello, Haskell!"

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Setup.hs Normal file
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import Distribution.Simple
main = defaultMain

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default.nix Normal file
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let
sources = import ./nix/sources.nix;
pkgs = import sources.nixpkgs {};
ghcVersion = "ghc865";
haskellPackages = pkgs.haskell.packages."${ghcVersion}";
hlib = pkgs.haskell.lib;
in haskellPackages.developPackage {
name = "haskell-playground";
root = ./.;
modifier = drv: hlib.overrideCabal drv (attrs: {
buildTools = (attrs.buildTools or []) ++ [
haskellPackages.cabal-install
];
});
}

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cabal-version: >=1.10
-- Initial package description 'haskell-playground.cabal' generated by
-- 'cabal init'. For further documentation, see
-- http://haskell.org/cabal/users-guide/
name: haskell-playground
version: 0.1.0.0
-- synopsis:
-- description:
-- bug-reports:
-- license:
license-file: LICENSE
author: Félix Baylac-Jacqué
maintainer: felix@alternativebit.fr
-- copyright:
-- category:
build-type: Simple
extra-source-files: CHANGELOG.md, readme.md
executable haskell-playground
main-is: Main.hs
-- other-modules:
-- other-extensions:
build-depends: base,
relude,
attoparsec,
megaparsec,
extra
-- hs-source-dirs:
default-language: Haskell2010

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{
"niv": {
"branch": "master",
"description": "Easy dependency management for Nix projects",
"homepage": "https://github.com/nmattia/niv",
"owner": "nmattia",
"repo": "niv",
"rev": "af958e8057f345ee1aca714c1247ef3ba1c15f5e",
"sha256": "1qjavxabbrsh73yck5dcq8jggvh3r2jkbr6b5nlz5d9yrqm9255n",
"type": "tarball",
"url": "https://github.com/nmattia/niv/archive/af958e8057f345ee1aca714c1247ef3ba1c15f5e.tar.gz",
"url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
},
"nixpkgs": {
"branch": "release-20.03",
"description": "Nix Packages collection",
"homepage": "",
"owner": "NixOS",
"repo": "nixpkgs",
"rev": "929768261a3ede470eafb58d5b819e1a848aa8bf",
"sha256": "0zi54vbfi6i6i5hdd4v0l144y1c8rg6hq6818jjbbcnm182ygyfa",
"type": "tarball",
"url": "https://github.com/NixOS/nixpkgs/archive/929768261a3ede470eafb58d5b819e1a848aa8bf.tar.gz",
"url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
}
}

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nix/sources.nix Normal file
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# This file has been generated by Niv.
let
#
# The fetchers. fetch_<type> fetches specs of type <type>.
#
fetch_file = pkgs: name: spec:
let
name' = sanitizeName name + "-src";
in
if spec.builtin or true then
builtins_fetchurl { inherit (spec) url sha256; name = name'; }
else
pkgs.fetchurl { inherit (spec) url sha256; name = name'; };
fetch_tarball = pkgs: name: spec:
let
name' = sanitizeName name + "-src";
in
if spec.builtin or true then
builtins_fetchTarball { name = name'; inherit (spec) url sha256; }
else
pkgs.fetchzip { name = name'; inherit (spec) url sha256; };
fetch_git = name: spec:
let
ref =
if spec ? ref then spec.ref else
if spec ? branch then "refs/heads/${spec.branch}" else
if spec ? tag then "refs/tags/${spec.tag}" else
abort "In git source '${name}': Please specify `ref`, `tag` or `branch`!";
in
builtins.fetchGit { url = spec.repo; inherit (spec) rev; inherit ref; };
fetch_local = spec: spec.path;
fetch_builtin-tarball = name: throw
''[${name}] The niv type "builtin-tarball" is deprecated. You should instead use `builtin = true`.
$ niv modify ${name} -a type=tarball -a builtin=true'';
fetch_builtin-url = name: throw
''[${name}] The niv type "builtin-url" will soon be deprecated. You should instead use `builtin = true`.
$ niv modify ${name} -a type=file -a builtin=true'';
#
# Various helpers
#
# https://github.com/NixOS/nixpkgs/pull/83241/files#diff-c6f540a4f3bfa4b0e8b6bafd4cd54e8bR695
sanitizeName = name:
(
concatMapStrings (s: if builtins.isList s then "-" else s)
(
builtins.split "[^[:alnum:]+._?=-]+"
((x: builtins.elemAt (builtins.match "\\.*(.*)" x) 0) name)
)
);
# The set of packages used when specs are fetched using non-builtins.
mkPkgs = sources: system:
let
sourcesNixpkgs =
import (builtins_fetchTarball { inherit (sources.nixpkgs) url sha256; }) { inherit system; };
hasNixpkgsPath = builtins.any (x: x.prefix == "nixpkgs") builtins.nixPath;
hasThisAsNixpkgsPath = <nixpkgs> == ./.;
in
if builtins.hasAttr "nixpkgs" sources
then sourcesNixpkgs
else if hasNixpkgsPath && ! hasThisAsNixpkgsPath then
import <nixpkgs> {}
else
abort
''
Please specify either <nixpkgs> (through -I or NIX_PATH=nixpkgs=...) or
add a package called "nixpkgs" to your sources.json.
'';
# The actual fetching function.
fetch = pkgs: name: spec:
if ! builtins.hasAttr "type" spec then
abort "ERROR: niv spec ${name} does not have a 'type' attribute"
else if spec.type == "file" then fetch_file pkgs name spec
else if spec.type == "tarball" then fetch_tarball pkgs name spec
else if spec.type == "git" then fetch_git name spec
else if spec.type == "local" then fetch_local spec
else if spec.type == "builtin-tarball" then fetch_builtin-tarball name
else if spec.type == "builtin-url" then fetch_builtin-url name
else
abort "ERROR: niv spec ${name} has unknown type ${builtins.toJSON spec.type}";
# If the environment variable NIV_OVERRIDE_${name} is set, then use
# the path directly as opposed to the fetched source.
replace = name: drv:
let
saneName = stringAsChars (c: if isNull (builtins.match "[a-zA-Z0-9]" c) then "_" else c) name;
ersatz = builtins.getEnv "NIV_OVERRIDE_${saneName}";
in
if ersatz == "" then drv else
# this turns the string into an actual Nix path (for both absolute and
# relative paths)
if builtins.substring 0 1 ersatz == "/" then /. + ersatz else /. + builtins.getEnv "PWD" + "/${ersatz}";
# Ports of functions for older nix versions
# a Nix version of mapAttrs if the built-in doesn't exist
mapAttrs = builtins.mapAttrs or (
f: set: with builtins;
listToAttrs (map (attr: { name = attr; value = f attr set.${attr}; }) (attrNames set))
);
# https://github.com/NixOS/nixpkgs/blob/0258808f5744ca980b9a1f24fe0b1e6f0fecee9c/lib/lists.nix#L295
range = first: last: if first > last then [] else builtins.genList (n: first + n) (last - first + 1);
# https://github.com/NixOS/nixpkgs/blob/0258808f5744ca980b9a1f24fe0b1e6f0fecee9c/lib/strings.nix#L257
stringToCharacters = s: map (p: builtins.substring p 1 s) (range 0 (builtins.stringLength s - 1));
# https://github.com/NixOS/nixpkgs/blob/0258808f5744ca980b9a1f24fe0b1e6f0fecee9c/lib/strings.nix#L269
stringAsChars = f: s: concatStrings (map f (stringToCharacters s));
concatMapStrings = f: list: concatStrings (map f list);
concatStrings = builtins.concatStringsSep "";
# https://github.com/NixOS/nixpkgs/blob/8a9f58a375c401b96da862d969f66429def1d118/lib/attrsets.nix#L331
optionalAttrs = cond: as: if cond then as else {};
# fetchTarball version that is compatible between all the versions of Nix
builtins_fetchTarball = { url, name ? null, sha256 }@attrs:
let
inherit (builtins) lessThan nixVersion fetchTarball;
in
if lessThan nixVersion "1.12" then
fetchTarball ({ inherit url; } // (optionalAttrs (!isNull name) { inherit name; }))
else
fetchTarball attrs;
# fetchurl version that is compatible between all the versions of Nix
builtins_fetchurl = { url, name ? null, sha256 }@attrs:
let
inherit (builtins) lessThan nixVersion fetchurl;
in
if lessThan nixVersion "1.12" then
fetchurl ({ inherit url; } // (optionalAttrs (!isNull name) { inherit name; }))
else
fetchurl attrs;
# Create the final "sources" from the config
mkSources = config:
mapAttrs (
name: spec:
if builtins.hasAttr "outPath" spec
then abort
"The values in sources.json should not have an 'outPath' attribute"
else
spec // { outPath = replace name (fetch config.pkgs name spec); }
) config.sources;
# The "config" used by the fetchers
mkConfig =
{ sourcesFile ? if builtins.pathExists ./sources.json then ./sources.json else null
, sources ? if isNull sourcesFile then {} else builtins.fromJSON (builtins.readFile sourcesFile)
, system ? builtins.currentSystem
, pkgs ? mkPkgs sources system
}: rec {
# The sources, i.e. the attribute set of spec name to spec
inherit sources;
# The "pkgs" (evaluated nixpkgs) to use for e.g. non-builtin fetchers
inherit pkgs;
};
in
mkSources (mkConfig {}) // { __functor = _: settings: mkSources (mkConfig settings); }

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# Haskell Playground
I use this project to quickly bootstrap a GHCi repl populated with all
the necessary dependencies to have fun with.
This playground relies on the Haskell Nixpkgs infrastructure to
bootstrap the env, allowing us to download the dependencies from the
NixOS binary cache instead of having to build them by ourselves.
You can bootstrap the env by via:
```
» nix-shell --pure
» ghci
```