nix: pin nixpkgs

Use `niv` to pin nixpkgs. Use the unstable branch because pythonPackage.dockerfile-parse isn't available in a release yet.
ChimeHH · Jul 19, 2019 · 79c6556 · 79c6556
1 parent 3ba1bb5
commit 79c6556
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diff --git a/nix/sources.json b/nix/sources.json
@@ -0,0 +1,13 @@
+{
+    "nixpkgs": {
+        "url": "https://github.com/NixOS/nixpkgs-channels/archive/362be9608c3e0dc5216e9d1d5f5c1a5643b7f7b1.tar.gz",
+        "owner": "NixOS",
+        "branch": "nixos-unstable",
+        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz",
+        "repo": "nixpkgs-channels",
+        "type": "tarball",
+        "sha256": "0934rhanamsnhawg15gg6cy9ird3c47hsqn5s46lq2n5kzl6v7ly",
+        "description": "Nixpkgs/NixOS branches that track the Nixpkgs/NixOS channels",
+        "rev": "362be9608c3e0dc5216e9d1d5f5c1a5643b7f7b1"
+    }
+}
diff --git a/nix/sources.nix b/nix/sources.nix
@@ -0,0 +1,67 @@
+# This file has been generated by Niv.
+
+# A record, from name to path, of the third-party packages
+with rec
+{
+  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.
+    '';
+
+  builtins_fetchTarball =
+      # fetchTarball version that is compatible between all the versions of
+      # Nix
+      { url, sha256 }@attrs:
+      let
+        inherit (builtins) lessThan nixVersion fetchTarball;
+      in
+        if lessThan nixVersion "1.12" then
+          fetchTarball { inherit url; }
+        else
+          fetchTarball attrs;
+
+  hasNixpkgsPath = (builtins.tryEval <nixpkgs>).success;
+  hasThisAsNixpkgsPath =
+    (builtins.tryEval <nixpkgs>).success && <nixpkgs> == ./.;
+
+  sources = builtins.fromJSON (builtins.readFile ./sources.json);
+
+  mapAttrs = builtins.mapAttrs or
+    (f: set: with builtins;
+      listToAttrs (map (attr: { name = attr; value = f attr set.${attr}; }) (attrNames set)));
+
+  getFetcher = spec:
+    let fetcherName =
+      if builtins.hasAttr "type" spec
+      then builtins.getAttr "type" spec
+      else "tarball";
+    in builtins.getAttr fetcherName {
+      "tarball" = pkgs.fetchzip;
+      "file" = pkgs.fetchurl;
+    };
+};
+# NOTE: spec must _not_ have an "outPath" attribute
+mapAttrs (_: spec:
+  if builtins.hasAttr "outPath" spec
+  then abort
+    "The values in sources.json should not have an 'outPath' attribute"
+  else
+    if builtins.hasAttr "url" spec && builtins.hasAttr "sha256" spec
+    then
+      spec //
+      { outPath = getFetcher spec { inherit (spec) url sha256; } ; }
+    else spec
+  ) sources
diff --git a/shell.nix b/shell.nix
@@ -1,5 +1,9 @@
 let
-  pkgs = import <nixpkgs> {};
+  # Use `niv update` to update nixpkgs.
+  # See https://github.com/nmattia/niv/
+  sources = import ./nix/sources.nix;
+
+  pkgs = import sources.nixpkgs { config = {}; overlays = []; };
 
   my-python = pkgs.python3.withPackages (p: with p; [
     defusedxml