Add tests for the shellFor function

Author: rvl

test/default.nix

@@ -15,6 +15,7 @@ in {
   with-packages = haskell.callPackage ./with-packages { inherit util; };
   builder-haddock = haskell.callPackage ./builder-haddock {};
   stack-simple = haskell.callPackage ./stack-simple {};
+  shell-for = haskell.callPackage ./shell-for { inherit util; };
 
   # Run unit tests with: nix-instantiate --eval --strict -A unit
   # An empty list means success.

test/shell-for/conduit.hs

@@ -0,0 +1,19 @@
+-- https://github.com/snoyberg/conduit#readme
+
+import Conduit
+import System.Directory (removeFile)
+
+main = do
+    -- Pure operations: summing numbers.
+    print $ runConduitPure $ yieldMany [1..10] .| sumC
+
+    -- Exception safe file access: copy a file.
+    writeFile "input.txt" "This is a test." -- create the source file
+    runConduitRes $ sourceFileBS "input.txt" .| sinkFile "output.txt" -- actual copying
+    readFile "output.txt" >>= putStrLn -- prove that it worked
+
+    -- Perform transformations.
+    print $ runConduitPure $ yieldMany [1..10] .| mapC (+ 1) .| sinkList
+
+    removeFile "input.txt"
+    removeFile "output.txt"

test/shell-for/default.nix

@@ -0,0 +1,48 @@
+{ stdenv, util, mkStackSnapshotPkgSet }:
+
+with stdenv.lib;
+with util;
+
+let
+  pkgSet = mkStackSnapshotPkgSet {
+    resolver = "lts-12.21";
+    # Work around a mismatch between stackage metadata and the
+    # libraries shipped with GHC.
+    # https://github.com/commercialhaskell/stackage/issues/4466
+    pkg-def-extras = [(hackage: {
+      packages = {
+        "transformers" = (((hackage.transformers)."0.5.6.2").revisions).default;
+        "process" = (((hackage.process)."1.6.5.0").revisions).default;
+      };
+    })];
+  };
+
+  env = pkgSet.config.hsPkgs.shellFor {
+    packages = ps: with ps; [ conduit conduit-extra resourcet ];
+    withHoogle = true;
+  };
+
+in
+  stdenv.mkDerivation {
+    name = "shell-for-test";
+
+    buildCommand = ''
+      ########################################################################
+      # test shell-for with an example program
+
+      printf "checking that the shell env has the dependencies...\n" >& 2
+      ${env.ghc}/bin/runghc ${./conduit.hs}
+
+      touch $out
+    '';
+
+    meta.platforms = platforms.all;
+    passthru = {
+      # Used for debugging with nix repl
+      inherit pkgSet;
+
+      # Used for testing externally with nix-shell (../tests.sh).
+      # This just adds cabal-install to the existing shell.
+      env = addCabalInstall env;
+    };
+}

test/tests.sh

@@ -54,4 +54,11 @@ nix-shell $NIX_BUILD_ARGS \
     --run 'cd cabal-simple && cabal new-build'
 echo >& 2
 
+printf "*** Checking shellFor works with a Stackage snapshot...\n" >& 2
+nix-shell $NIX_BUILD_ARGS \
+    --pure ./default.nix \
+    -A shell-for.env \
+    --run 'cd shell-for && runghc conduit.hs'
+echo >& 2
+
 printf "\n*** Finished successfully\n" >& 2