From 8bf10a4fc6f03a1aa6b62395908f0b684ec57d06 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?L=C3=A1szl=C3=B3=20Vask=C3=B3?= <laszlo.vasko@outlook.com>
Date: Wed, 19 Feb 2020 23:48:39 +0100
Subject: [PATCH] Updating sources using `niv` to track versions

It is nice tool for the job I have not yet known about
---
 default.nix      |  24 +++----
 derivations.json |  52 ----------------
 derivations.lock | 158 -----------------------------------------------
 nix/sources.json | 158 +++++++++++++++++++++++++++++++++++++++++++++++
 nix/sources.nix  | 128 ++++++++++++++++++++++++++++++++++++++
 5 files changed, 296 insertions(+), 224 deletions(-)
 delete mode 100644 derivations.json
 delete mode 100644 derivations.lock
 create mode 100644 nix/sources.json
 create mode 100644 nix/sources.nix

diff --git a/default.nix b/default.nix
index 201dcda..d9faa5b 100644
--- a/default.nix
+++ b/default.nix
@@ -53,12 +53,10 @@
 , writeTextDir }:
 
 let
-  lock = pkgs.callPackage
-    "${builtins.fetchTarball https://github.com/vlaci/nix-lock/archive/develop.tar.gz}/lock.nix" {
-      path = ./derivations.lock;
-      overrides = dependencyOverrides;
-    };
-
+  sources = import ./nix/sources.nix;
+  lock = p: if dependencyOverrides ? p
+            then dependencyOverrides.${p}
+            else sources.${p};
   # Packages we need to get the default doom configuration run
   overrides = self: super: {
     evil-escape = super.evil-escape.overrideAttrs (esuper: {
@@ -67,7 +65,7 @@ let
     straightBuild = { pname, ... }@args: self.trivialBuild ({
       ename = pname;
       version = "1";
-      src = lock.get pname;
+      src = lock pname;
       buildPhase = ":";
     } // args);
     doom-snippets = self.straightBuild {
@@ -105,19 +103,17 @@ let
       pname = "php-extras";
     };
     rotate-text = self.straightBuild {
-      pname = "rotate-text";
-      ename = "rotate-text.el";
+      pname = "rotate-text.el";
     };
     so-long = self.straightBuild {
-      pname = "so-long";
-      ename = "emacs-so-long";
+      pname = "emacs-so-long";
     };
   };
 
   # Stage 1: prepare source for byte-compilation
   doomSrc = stdenv.mkDerivation {
     name = "doom-src";
-    src = lock.get "doom-emacs";
+    src = lock "doom-emacs";
     phases = ["unpackPhase" "patchPhase" "installPhase"];
     patches = [
       (substituteAll {
@@ -132,12 +128,12 @@ let
   };
 
   # Bundled version of `emacs-overlay`
-  emacs-overlay = import (lock.get "emacs-overlay") pkgs pkgs;
+  emacs-overlay = import (lock "emacs-overlay") pkgs pkgs;
 
   # Stage 2: install dependencies and byte-compile prepared source
   doomLocal =
     let
-      straight-env = pkgs.callPackage (lock.get "nix-straight.el") {
+      straight-env = pkgs.callPackage (lock "nix-straight.el") {
         emacsPackages =
           if bundledPackages then
             let
diff --git a/derivations.json b/derivations.json
deleted file mode 100644
index 8e92675..0000000
--- a/derivations.json
+++ /dev/null
@@ -1,52 +0,0 @@
-{
-    "doom-emacs": {
-        "repo": "doom-emacs",
-        "owner": "hlissner",
-        "rev": "develop"
-    },
-    "nix-straight.el": {
-        "owner": "vlaci",
-        "repo": "nix-straight.el",
-        "rev": "v1.2.0"
-    },
-    "doom-snippets": {
-        "owner": "hlissner",
-        "repo": "doom-snippets"
-    },
-    "evil-markdown": {
-        "owner": "Somelauw",
-        "repo": "evil-markdown"
-    },
-    "evil-org-mode": {
-        "owner": "hlissner",
-        "repo": "evil-org-mode"
-    },
-    "evil-quick-diff": {
-        "owner": "rgrinberg",
-        "repo": "evil-quick-diff"
-    },
-    "org-mode": {
-        "owner": "emacs-straight",
-        "repo": "org-mode"
-    },
-    "org-yt": {
-        "owner": "TobiasZawada",
-        "repo": "org-yt"
-    },
-    "php-extras": {
-        "owner": "arnested",
-        "repo": "php-extras"
-    },
-    "rotate-text": {
-        "owner": "debug-ito",
-        "repo": "rotate-text.el"
-    },
-    "so-long": {
-        "owner": "hlissner",
-        "repo": "emacs-so-long"
-    },
-    "emacs-overlay": {
-        "owner": "nix-community",
-        "repo": "emacs-overlay"
-    }
-}
diff --git a/derivations.lock b/derivations.lock
deleted file mode 100644
index fb5d75d..0000000
--- a/derivations.lock
+++ /dev/null
@@ -1,158 +0,0 @@
-{
-    "doom-emacs": {
-        "fetcher": "fetchFromGitHub",
-        "args": {
-            "owner": "hlissner",
-            "repo": "doom-emacs",
-            "rev": "b0978a4526cfd78bb18e5279909c19bee97e9878",
-            "sha256": "0ydjzp87zcz4bfnqcqs0fyxdbv4273h21ir1sjny2lln3d3w7zzw"
-        },
-        "meta": {
-            "updated": "2020-02-15T09:39:33+00:00",
-            "rev": "b0978a4526cfd78bb18e5279909c19bee97e9878"
-        }
-    },
-    "nix-straight.el": {
-        "fetcher": "fetchFromGitHub",
-        "args": {
-            "owner": "vlaci",
-            "repo": "nix-straight.el",
-            "rev": "446f3d70f1816305130f307c0cf2bc8db77ed698",
-            "sha256": "1p4yp46kwhii8w9yf882fca9r3addn91wg6f4mv62wnkfm0i6q0f"
-        },
-        "meta": {
-            "updated": "2020-01-25T18:43:31+00:00",
-            "rev": "446f3d70f1816305130f307c0cf2bc8db77ed698"
-        }
-    },
-    "org-yt": {
-        "fetcher": "fetchFromGitHub",
-        "args": {
-            "owner": "TobiasZawada",
-            "repo": "org-yt",
-            "rev": "40cc1ac76d741055cbefa13860d9f070a7ade001",
-            "sha256": "0jsm3azb7lwikvc53z4p91av8qvda9s15wij153spkgjp83kld3p"
-        },
-        "meta": {
-            "updated": "2019-10-25T22:28:27+00:00",
-            "rev": "40cc1ac76d741055cbefa13860d9f070a7ade001"
-        }
-    },
-    "emacs-overlay": {
-        "fetcher": "fetchFromGitHub",
-        "args": {
-            "owner": "nix-community",
-            "repo": "emacs-overlay",
-            "rev": "af3182aa950a3c591df7d2007fedf658c6cbc687",
-            "sha256": "09yqs9h4zwcshhkvzdzlkixs1mprdrmknh05kqv7c3pq1ir0daiz"
-        },
-        "meta": {
-            "updated": "2020-02-15T09:39:40+00:00",
-            "rev": "af3182aa950a3c591df7d2007fedf658c6cbc687"
-        }
-    },
-    "evil-markdown": {
-        "fetcher": "fetchFromGitHub",
-        "args": {
-            "owner": "Somelauw",
-            "repo": "evil-markdown",
-            "rev": "46cd81b37991c4325fc24015a610f832b0ff995d",
-            "sha256": "0mad8sp5y9vyk28595qygspnyh8bfmb1fbxjlw70qwc1kdn822n4"
-        },
-        "meta": {
-            "updated": "2019-11-23T14:33:01+00:00",
-            "rev": "46cd81b37991c4325fc24015a610f832b0ff995d"
-        }
-    },
-    "php-extras": {
-        "fetcher": "fetchFromGitHub",
-        "args": {
-            "owner": "arnested",
-            "repo": "php-extras",
-            "rev": "81ebd7c1a8c8d02b2775d4cdbf73653feb608a7c",
-            "sha256": "181dg1z00qagwb9qd45fpcrya32mdgj8dnkpnfv52lqmi94vvzg0"
-        },
-        "meta": {
-            "updated": "2019-11-23T14:33:03+00:00",
-            "rev": "81ebd7c1a8c8d02b2775d4cdbf73653feb608a7c"
-        }
-    },
-    "so-long": {
-        "fetcher": "fetchFromGitHub",
-        "args": {
-            "owner": "hlissner",
-            "repo": "emacs-so-long",
-            "rev": "ed666b0716f60e8988c455804de24b55919e71ca",
-            "sha256": "0bc6nrdrvj422g15zqn00vs7ga9bq5c3hdg7ml1kls8rxp6bk1n4"
-        },
-        "meta": {
-            "updated": "2019-12-21T13:21:48+00:00",
-            "rev": "ed666b0716f60e8988c455804de24b55919e71ca"
-        }
-    },
-    "evil-quick-diff": {
-        "fetcher": "fetchFromGitHub",
-        "args": {
-            "owner": "rgrinberg",
-            "repo": "evil-quick-diff",
-            "rev": "69c883720b30a892c63bc89f49d4f0e8b8028908",
-            "sha256": "15cww264lhddxh0d2ca5qd5nq5pda8hs4nj8mcpb5xlnmkayav50"
-        },
-        "meta": {
-            "updated": "2019-12-01T14:49:48+00:00",
-            "rev": "69c883720b30a892c63bc89f49d4f0e8b8028908"
-        }
-    },
-    "evil-org-mode": {
-        "fetcher": "fetchFromGitHub",
-        "args": {
-            "owner": "hlissner",
-            "repo": "evil-org-mode",
-            "rev": "4d44e9bbdc3ae35d0050ca298886710f6531f434",
-            "sha256": "0kp19q58rqi2x31g5fqqy5rzw7ymxsa9iaxj3f9rya9zyyma6g59"
-        },
-        "meta": {
-            "updated": "2020-01-07T11:56:38+00:00",
-            "rev": "4d44e9bbdc3ae35d0050ca298886710f6531f434"
-        }
-    },
-    "org-mode": {
-        "fetcher": "fetchFromGitHub",
-        "args": {
-            "owner": "emacs-straight",
-            "repo": "org-mode",
-            "rev": "e361c640435af947fab201c1fe60f25843edb5e9",
-            "sha256": "15hbrsz45zhvh09qsijmw9x38zzaiymsmczafyfql68ar2s1slgj"
-        },
-        "meta": {
-            "updated": "2020-02-15T09:39:37+00:00",
-            "rev": "e361c640435af947fab201c1fe60f25843edb5e9"
-        }
-    },
-    "doom-snippets": {
-        "fetcher": "fetchFromGitHub",
-        "args": {
-            "owner": "hlissner",
-            "repo": "doom-snippets",
-            "rev": "4a0e675e1a4713dc8b3c020b30cad18ef4d7401d",
-            "sha256": "0b3vdwm9brnjgivxd3icz5znjhjhzqkd38nn9qamk4n09d7h2nd7"
-        },
-        "meta": {
-            "updated": "2020-02-15T09:48:50+00:00",
-            "rev": "4a0e675e1a4713dc8b3c020b30cad18ef4d7401d"
-        }
-    },
-    "rotate-text": {
-        "fetcher": "fetchFromGitHub",
-        "args": {
-            "owner": "debug-ito",
-            "repo": "rotate-text.el",
-            "rev": "48f193697db996855aee1ad2bc99b38c6646fe76",
-            "sha256": "02fkv45nbbqrv12czlinpr8qpsd7yjdhr628hl58n42w560qxrs8"
-        },
-        "meta": {
-            "updated": "2020-02-15T09:48:53+00:00",
-            "rev": "48f193697db996855aee1ad2bc99b38c6646fe76"
-        }
-    }
-}
diff --git a/nix/sources.json b/nix/sources.json
new file mode 100644
index 0000000..cc38ff4
--- /dev/null
+++ b/nix/sources.json
@@ -0,0 +1,158 @@
+{
+    "doom-emacs": {
+        "branch": "develop",
+        "description": "An Emacs configuration for the stubborn martian vimmer",
+        "homepage": "",
+        "owner": "hlissner",
+        "repo": "doom-emacs",
+        "rev": "f645675e4c03c613c76e36230594e4b0ea7fbaeb",
+        "sha256": "1payhw79x90ms3ahr09qkzagg0dg40js5fsdr8wwyf0si8nl9awr",
+        "type": "tarball",
+        "url": "https://github.com/hlissner/doom-emacs/archive/f645675e4c03c613c76e36230594e4b0ea7fbaeb.tar.gz",
+        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
+    },
+    "doom-snippets": {
+        "branch": "master",
+        "description": "The Doom Emacs snippets library",
+        "homepage": "",
+        "owner": "hlissner",
+        "repo": "doom-snippets",
+        "rev": "1449fdaf9a3755c16c6b5b7c0de36b9de520afed",
+        "sha256": "0mbjdgn602bgnx2mi5925m4ss4y95ywh7jk1qnka74zpa34dfgnq",
+        "type": "tarball",
+        "url": "https://github.com/hlissner/doom-snippets/archive/1449fdaf9a3755c16c6b5b7c0de36b9de520afed.tar.gz",
+        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
+    },
+    "emacs-overlay": {
+        "branch": "master",
+        "description": "Bleeding edge emacs overlay [maintainer=@adisbladis] ",
+        "homepage": "",
+        "owner": "nix-community",
+        "repo": "emacs-overlay",
+        "rev": "34b22694b4859416d5b84dbfc423e4444dc52a62",
+        "sha256": "0yawmp08md1mzzvixhyn9lkv7jkwya8xd76pskbp1k1czqlsn5p9",
+        "type": "tarball",
+        "url": "https://github.com/nix-community/emacs-overlay/archive/34b22694b4859416d5b84dbfc423e4444dc52a62.tar.gz",
+        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
+    },
+    "emacs-so-long": {
+        "branch": "master",
+        "description": "A mirror of the so-long package (until it's on ELPA)",
+        "homepage": "https://git.savannah.gnu.org/git/so-long.git/",
+        "owner": "hlissner",
+        "repo": "emacs-so-long",
+        "rev": "ed666b0716f60e8988c455804de24b55919e71ca",
+        "sha256": "0bc6nrdrvj422g15zqn00vs7ga9bq5c3hdg7ml1kls8rxp6bk1n4",
+        "type": "tarball",
+        "url": "https://github.com/hlissner/emacs-so-long/archive/ed666b0716f60e8988c455804de24b55919e71ca.tar.gz",
+        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
+    },
+    "evil-markdown": {
+        "branch": "master",
+        "description": "Integrates emacs evil and markdown",
+        "homepage": null,
+        "owner": "Somelauw",
+        "repo": "evil-markdown",
+        "rev": "46cd81b37991c4325fc24015a610f832b0ff995d",
+        "sha256": "0mad8sp5y9vyk28595qygspnyh8bfmb1fbxjlw70qwc1kdn822n4",
+        "type": "tarball",
+        "url": "https://github.com/Somelauw/evil-markdown/archive/46cd81b37991c4325fc24015a610f832b0ff995d.tar.gz",
+        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
+    },
+    "evil-org-mode": {
+        "branch": "master",
+        "description": "Supplemental evil-mode keybindings to emacs org-mode",
+        "homepage": null,
+        "owner": "hlissner",
+        "repo": "evil-org-mode",
+        "rev": "4d44e9bbdc3ae35d0050ca298886710f6531f434",
+        "sha256": "0kp19q58rqi2x31g5fqqy5rzw7ymxsa9iaxj3f9rya9zyyma6g59",
+        "type": "tarball",
+        "url": "https://github.com/hlissner/evil-org-mode/archive/4d44e9bbdc3ae35d0050ca298886710f6531f434.tar.gz",
+        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
+    },
+    "evil-quick-diff": {
+        "branch": "master",
+        "description": "linediff.vim for evil",
+        "homepage": null,
+        "owner": "rgrinberg",
+        "repo": "evil-quick-diff",
+        "rev": "69c883720b30a892c63bc89f49d4f0e8b8028908",
+        "sha256": "15cww264lhddxh0d2ca5qd5nq5pda8hs4nj8mcpb5xlnmkayav50",
+        "type": "tarball",
+        "url": "https://github.com/rgrinberg/evil-quick-diff/archive/69c883720b30a892c63bc89f49d4f0e8b8028908.tar.gz",
+        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
+    },
+    "nix-straight.el": {
+        "branch": "v1.2.0",
+        "description": null,
+        "homepage": null,
+        "owner": "vlaci",
+        "repo": "nix-straight.el",
+        "rev": "446f3d70f1816305130f307c0cf2bc8db77ed698",
+        "sha256": "1p4yp46kwhii8w9yf882fca9r3addn91wg6f4mv62wnkfm0i6q0f",
+        "type": "tarball",
+        "url": "https://github.com/vlaci/nix-straight.el/archive/446f3d70f1816305130f307c0cf2bc8db77ed698.tar.gz",
+        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
+    },
+    "nixpkgs": {
+        "branch": "nixos-19.09",
+        "description": "A read-only mirror of NixOS/nixpkgs tracking the released channels. Send issues and PRs to",
+        "homepage": "https://github.com/NixOS/nixpkgs",
+        "owner": "NixOS",
+        "repo": "nixpkgs-channels",
+        "rev": "8731aaaf8b30888bc24994096db830993090d7c4",
+        "sha256": "1hcc89rxi47nb0mpk05nl9rbbb04kfw97xfydhpmmgh57yrp3zqa",
+        "type": "tarball",
+        "url": "https://github.com/NixOS/nixpkgs-channels/archive/8731aaaf8b30888bc24994096db830993090d7c4.tar.gz",
+        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
+    },
+    "org-mode": {
+        "branch": "master",
+        "description": "Mirror of org-mode from orgmode.org",
+        "homepage": "https://code.orgmode.org/bzg/org-mode",
+        "owner": "emacs-straight",
+        "repo": "org-mode",
+        "rev": "bc75b75d9f15da387adf47b6d53a21fae09670b0",
+        "sha256": "1sjy57zv4638r0ysz58jrckslz3mc5myi3lvj9lzax2klxndrv6s",
+        "type": "tarball",
+        "url": "https://github.com/emacs-straight/org-mode/archive/bc75b75d9f15da387adf47b6d53a21fae09670b0.tar.gz",
+        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
+    },
+    "org-yt": {
+        "branch": "master",
+        "description": "Youtube links in org-mode, see  https://emacs.stackexchange.com/questions/38098/org-mode-custom-youtube-link-syntax",
+        "homepage": null,
+        "owner": "TobiasZawada",
+        "repo": "org-yt",
+        "rev": "40cc1ac76d741055cbefa13860d9f070a7ade001",
+        "sha256": "0jsm3azb7lwikvc53z4p91av8qvda9s15wij153spkgjp83kld3p",
+        "type": "tarball",
+        "url": "https://github.com/TobiasZawada/org-yt/archive/40cc1ac76d741055cbefa13860d9f070a7ade001.tar.gz",
+        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
+    },
+    "php-extras": {
+        "branch": "develop",
+        "description": "Extra features for Emacs `php-mode'.",
+        "homepage": "http://marmalade-repo.org/packages/php-extras",
+        "owner": "arnested",
+        "repo": "php-extras",
+        "rev": "d410c5af663c30c01d461ac476d1cbfbacb49367",
+        "sha256": "0mcgwisnqplav0ga8xqqw72523iv841wp2cyw7d4lkzgpiav51dg",
+        "type": "tarball",
+        "url": "https://github.com/arnested/php-extras/archive/d410c5af663c30c01d461ac476d1cbfbacb49367.tar.gz",
+        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
+    },
+    "rotate-text.el": {
+        "branch": "master",
+        "description": "Emacs: cycle through words, symbols and patterns",
+        "homepage": "http://nschum.de/src/emacs/rotate-text/",
+        "owner": "debug-ito",
+        "repo": "rotate-text.el",
+        "rev": "48f193697db996855aee1ad2bc99b38c6646fe76",
+        "sha256": "02fkv45nbbqrv12czlinpr8qpsd7yjdhr628hl58n42w560qxrs8",
+        "type": "tarball",
+        "url": "https://github.com/debug-ito/rotate-text.el/archive/48f193697db996855aee1ad2bc99b38c6646fe76.tar.gz",
+        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
+    }
+}
diff --git a/nix/sources.nix b/nix/sources.nix
new file mode 100644
index 0000000..4c0351c
--- /dev/null
+++ b/nix/sources.nix
@@ -0,0 +1,128 @@
+# This file has been generated by Niv.
+
+let
+
+  #
+  # The fetchers. fetch_<type> fetches specs of type <type>.
+  #
+
+  fetch_file = spec:
+    if spec.builtin or true then
+      builtins_fetchurl { inherit (spec) url sha256; }
+    else
+      pkgs.fetchurl { inherit (spec) url sha256; };
+
+  fetch_tarball = spec:
+    if spec.builtin or true then
+      builtins_fetchTarball { inherit (spec) url sha256; }
+    else
+      pkgs.fetchzip { inherit (spec) url sha256; };
+
+  fetch_git = spec:
+      builtins.fetchGit { url = spec.repo; inherit (spec) rev ref; };
+
+  fetch_builtin-tarball = spec:
+    builtins.trace
+      ''
+        WARNING:
+          The niv type "builtin-tarball" will soon be deprecated. You should
+          instead use `builtin = true`.
+
+          $ niv modify <package> -a type=tarball -a builtin=true
+      ''
+      builtins_fetchTarball { inherit (spec) url sha256; };
+
+  fetch_builtin-url = spec:
+    builtins.trace
+      ''
+        WARNING:
+          The niv type "builtin-url" will soon be deprecated. You should
+          instead use `builtin = true`.
+
+          $ niv modify <package> -a type=file -a builtin=true
+      ''
+      (builtins_fetchurl { inherit (spec) url sha256; });
+
+  #
+  # The sources to fetch.
+  #
+
+  sources = builtins.fromJSON (builtins.readFile ./sources.json);
+
+  #
+  # Various helpers
+  #
+
+  # The set of packages used when specs are fetched using non-builtins.
+  pkgs =
+    if hasNixpkgsPath
+    then
+      if hasThisAsNixpkgsPath
+      then import (builtins_fetchTarball { inherit (sources_nixpkgs) url sha256; }) {}
+      else import <nixpkgs> {}
+    else
+      import (builtins_fetchTarball { inherit (sources_nixpkgs) url sha256; }) {};
+
+  sources_nixpkgs =
+    if builtins.hasAttr "nixpkgs" sources
+    then sources.nixpkgs
+    else abort
+      ''
+        Please specify either <nixpkgs> (through -I or NIX_PATH=nixpkgs=...) or
+        add a package called "nixpkgs" to your sources.json.
+      '';
+
+  hasNixpkgsPath = (builtins.tryEval <nixpkgs>).success;
+  hasThisAsNixpkgsPath =
+    (builtins.tryEval <nixpkgs>).success && <nixpkgs> == ./.;
+
+  # The actual fetching function.
+  fetch = 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 spec
+    else if spec.type == "tarball" then fetch_tarball spec
+    else if spec.type == "git" then fetch_git spec
+    else if spec.type == "builtin-tarball" then fetch_builtin-tarball spec
+    else if spec.type == "builtin-url" then fetch_builtin-url spec
+    else
+      abort "ERROR: niv spec ${name} has unknown type ${builtins.toJSON spec.type}";
+
+  # Ports of functions for older nix versions
+
+  # a Nix version of mapAttrs if the built-in doesn't exist
+  mapAttrs = builtins.mapAttrs or (
+    f: set: with builtins;
+    listToAttrs (map (attr: { name = attr; value = f attr set.${attr}; }) (attrNames set))
+  );
+
+  # fetchTarball version that is compatible between all the versions of Nix
+  builtins_fetchTarball = { url, sha256 }@attrs:
+    let
+      inherit (builtins) lessThan nixVersion fetchTarball;
+    in
+      if lessThan nixVersion "1.12" then
+        fetchTarball { inherit url; }
+      else
+        fetchTarball attrs;
+
+  # fetchurl version that is compatible between all the versions of Nix
+  builtins_fetchurl = { url, sha256 }@attrs:
+    let
+      inherit (builtins) lessThan nixVersion fetchurl;
+    in
+      if lessThan nixVersion "1.12" then
+        fetchurl { inherit url; }
+      else
+        fetchurl attrs;
+
+in
+mapAttrs (
+  name: spec:
+    if builtins.hasAttr "outPath" spec
+    then abort
+      "The values in sources.json should not have an 'outPath' attribute"
+    else
+      spec // { outPath = fetch name spec; }
+) sources