Fix evaluation on Hydra (#153)

* Fix eval on Hydra

* Bump nixpkgs to latest 19.03

* Change unit tests into a derivation

Prevents Hydra from complaining about them.

* Add unpacked source pins to Hydra jobset

So that they are cached.

default.nix

@@ -43,18 +43,20 @@ let
   cleanSourceHaskell = pkgs.callPackage ./lib/clean-source-haskell.nix {};
 
   # All packages from Hackage as Nix expressions
-  hackage = import (fetchExternal {
+  hackageSrc = fetchExternal {
     name     = "hackage-exprs-source";
     specJSON = hackageSourceJSON;
     override = "hackage";
-  });
+  };
+  hackage = import hackageSrc;
 
   # The set of all Stackage snapshots
-  stackage = import (fetchExternal {
+  stackageSrc = fetchExternal {
     name     = "stackage-snapshot-source";
     specJSON = stackageSourceJSON;
     override = "stackage";
-  });
+  };
+  stackage = import stackageSrc;
 
   packages = self: ({
     # Utility functions for working with the component builder.
@@ -196,6 +198,11 @@ let
       inherit (pkgs.haskellPackages) hpack;
       inherit (self) nix-tools;
     };
+
+    # References to the unpacked sources, for caching in a Hydra jobset.
+    source-pins = self.callPackage ./lib/make-source-pins.nix {
+      sources = [ hackageSrc stackageSrc pkgs.path ];
+    };
   });
 
 in

lib/make-source-pins.nix

@@ -0,0 +1,11 @@
+# Writes the store paths of a list of sources into a file.
+# If this derivation is built by Hydra, then the sources will
+# be kept and will be available to download from the binary cache.
+{ lib, writeTextFile
+, sources # A list of paths
+}:
+
+writeTextFile {
+  name = "haskell.nix-source-pins";
+  text = lib.concatMapStringsSep "\n" toString sources;
+}

nixpkgs/default.nix

@@ -2,5 +2,9 @@ let
   fetch = jsonFile:
     with builtins;
     let spec = fromJSON (readFile jsonFile);
-    in fetchTarball { inherit (spec) sha256; url = "${spec.url}/archive/${spec.rev}.tar.gz"; };
+    in fetchTarball {
+      name = "nixpkgs";
+      inherit (spec) sha256;
+      url = "${spec.url}/archive/${spec.rev}.tar.gz";
+    };
 in import (fetch ./github.json)

nixpkgs/github.json

@@ -1,7 +1,7 @@
 {
-  "url": "https://github.com/nixos/nixpkgs",
-  "rev": "db85ded4aae63508934dc42064c7fbff16e0ec21",
+  "url": "https://github.com/NixOS/nixpkgs",
+  "rev": "0728c3e026e3ac2542a9673d57533829e552e218",
   "date": "2019-05-17T15:35:26+02:00",
-  "sha256": "0b91n0s5zaamxh9842ns11s40678sv4pbpxaxdqnrnkrkp8pn9gy",
+  "sha256": "0sp8giack8na9hdm8ivk969mpwfcavqrfy7kncx0a1hs1ykw15hy",
   "fetchSubmodules": false
 }

release.nix

@@ -1,6 +1,7 @@
 let
   haskell = import ./default.nix {};
 in {
-  inherit (haskell) nix-tools;
+  inherit (haskell) nix-tools source-pins;
+
   tests = import ./test { inherit haskell; };
 }

test/default.nix

@@ -18,12 +18,16 @@ in {
   stack-simple = haskell.callPackage ./stack-simple {};
   snapshots = haskell.callPackage ./snapshots {};
   shell-for = haskell.callPackage ./shell-for {};
-  callStackToNix = haskell.callPackage ./callStackToNix {};
-  callCabalProjectToNix = haskell.callPackage ./call-cabal-project-to-nix {};
+  # callStackToNix = haskell.callPackage ./callStackToNix {};
+  # callCabalProjectToNix = haskell.callPackage ./call-cabal-project-to-nix {};
 
-  # Run unit tests with: nix-instantiate --eval --strict -A unit
+  # Run unit tests with: nix-instantiate --eval --strict -A unit.tests
   # An empty list means success.
-  unit = haskell.callPackage ./unit.nix {};
+  unit = let
+    tests = haskell.callPackage ./unit.nix {};
+  in runCommand "unit-tests" { passthru = { inherit tests; }; }
+     (lib.concatMapStringsSep "\n" (t: "echo ${t.name} failed") tests +
+      (if builtins.length tests == 0 then "\ntouch $out" else "\nexit 1"));
 }
 
 ## more possible test cases

test/tests.sh

@@ -16,7 +16,7 @@ nix build $NIX_BUILD_ARGS --no-link --keep-going -f ./default.nix
 echo >& 2
 
 printf "*** Running the unit tests... " >& 2
-res=$(nix-instantiate --eval --json --strict ./default.nix -A unit)
+res=$(nix-instantiate --eval --json --strict ./default.nix -A unit.tests)
 num_failed=$(jq length <<< "$res")
 if [ $num_failed -eq 0 ]; then
   printf "PASSED\n" >& 2