download stack resolver if a sha256 is provided (#748)

This change allows a resolverSha256 to be passed to stackProject.
When provided the resolver found in the stack.yaml is fetched
using this sha256 and the uri string is replaced with the
path to the fetched version.

lib/call-stack-to-nix.nix

@@ -5,21 +5,26 @@
  *
  * see also `call-cabal-project-to-nix`!
  */
-{ runCommand, nix-tools, pkgs, mkCacheFile, materialize }:
+{ runCommand, nix-tools, pkgs, mkCacheFile, materialize, haskellLib }:
 { name ? src.name or null # optional name for better error messages
 , src
-, stackYaml ? null
+, stackYaml ? "stack.yaml"
 , ignorePackageYaml ? false
 , cache ? null
 , stack-sha256 ? null
+, resolverSha256 ? null
 , materialized ? null # Location of a materialized copy of the nix files
 , checkMaterialization ? null # If true the nix files will be generated used to check plan-sha256 and material
 , ... }:
 let
+  inherit (haskellLib.fetchResolver {
+      inherit src stackYaml resolverSha256;
+    }) resolver fetchedResolver;
+
   subDir' = src.origSubDir or "";
   stackToNixArgs = builtins.concatStringsSep " " [
     "--full"
-    "--stack-yaml=${src}/${if stackYaml == null then "stack.yaml" else stackYaml}"
+    "--stack-yaml=$SRC/${stackYaml}"
     (if ignorePackageYaml then "--ignore-package-yaml" else "")
     "-o ."
   ];
@@ -31,7 +36,7 @@ let
   } // pkgs.lib.optionalAttrs (checkMaterialization != null) {
     inherit checkMaterialization;
   }) (runCommand (if name == null then "stack-to-nix-pkgs" else name + "-stack-to-nix-pkgs") {
-    nativeBuildInputs = [ nix-tools pkgs.nix-prefetch-git pkgs.cacert ];
+    nativeBuildInputs = [ nix-tools pkgs.nix-prefetch-git pkgs.cacert pkgs.xorg.lndir ];
     # Needed or stack-to-nix will die on unicode inputs
     LOCALE_ARCHIVE = pkgs.lib.optionalString (pkgs.stdenv.hostPlatform.libc == "glibc") "${pkgs.glibcLocales}/lib/locale/locale-archive";
     LANG = "en_US.UTF-8";
@@ -39,15 +44,32 @@ let
     preferLocalBuild = false;
   } (''
     mkdir -p $out${subDir'}
-  '' + pkgs.lib.optionalString (cache != null) ''
-    cp ${mkCacheFile cache}/.stack-to-nix.cache* $out${subDir'}
-  '' + ''
+    ${
+    # If no resolver was fetched use the original stack.yaml
+    if fetchedResolver == null
+    then ''
+      SRC=${src}
+    ''
+    else
+      # Replace the resolver path in the stack.yaml with the fetched version
+      ''
+      SRC=$(mktemp -d)
+      cd $SRC
+      lndir -silent "${src}/." $SRC
+      rm ${stackYaml}
+      cp ${src}/${stackYaml} .
+      chmod +w ${stackYaml}
+      substituteInPlace ${stackYaml} --replace "${resolver}" "${fetchedResolver}"
+    ''}
+    ${pkgs.lib.optionalString (cache != null) ''
+      cp ${mkCacheFile cache}/.stack-to-nix.cache* $out${subDir'}
+    ''}
     (cd $out${subDir'} && stack-to-nix ${stackToNixArgs})
 
     # We need to strip out any references to $src, as those won't
     # be accessable in restricted mode.
     for nixf in $(find $out -name "*.nix" -type f); do
-      substituteInPlace $nixf --replace "${src}" "."
+      substituteInPlace $nixf --replace "$SRC" "."
     done
 
     # move pkgs.nix to default.nix ensure we can just nix `import` the result.

lib/default.nix

@@ -261,4 +261,9 @@ in {
     if lib.isAttrs versionOrArgs
       then versionOrArgs
       else { version = versionOrArgs; };
+
+  # Find the resolver in the stack.yaml file and fetch it if a sha256 value is provided
+  fetchResolver = import ./fetch-resolver.nix {
+    inherit (pkgs.evalPackages) pkgs;
+  }; 
 }

lib/fetch-resolver.nix

@@ -0,0 +1,33 @@
+# Find the resolver in the stack.yaml file and fetch it if a sha256 value is provided
+{ pkgs }:
+{ src
+, stackYaml ? "stack.yaml"
+, resolverSha256 ? null
+}:
+let
+    # Using origSrcSubDir bypasses any cleanSourceWith so that it will work when
+    # access to the store is restricted.  If origSrc was already in the store
+    # you can pass the project in as a string.
+    rawStackYaml = builtins.readFile ((src.origSrcSubDir or src) + ("/" + stackYaml));
+
+    # Determine the resolver as it may point to another file we need
+    # to look at.
+    resolver =
+      let
+        rs = pkgs.lib.lists.concatLists (
+          pkgs.lib.lists.filter (l: l != null)
+            (builtins.map (l: builtins.match "^resolver: *(.*)" l)
+              (pkgs.lib.splitString "\n" rawStackYaml)));
+      in
+        pkgs.lib.lists.head (rs ++ [ null ]);
+
+    # If we found a resolver andwe have a resolverSha256 then we should download it.
+    fetchedResolver =
+      if resolver != null && resolverSha256 != null
+        then pkgs.fetchurl {
+          url = resolver;
+          sha256 = resolverSha256;
+        }
+        else null;
+
+in { inherit resolver fetchedResolver; }

lib/stack-cache-generator.nix

@@ -13,6 +13,7 @@
   if sha256map != null
     then { location, tag, ...}: sha256map."${location}"."${tag}"
     else _: null
+, resolverSha256 ? null
 , ...
 }:
 let
@@ -20,21 +21,9 @@ let
     # we want to avoid recalculating the cache unless the stack.yaml file
     # changes.
 
-    # Using origSrcSubDir bypasses any cleanSourceWith so that it will work when
-    # access to the store is restricted.  If origSrc was already in the store
-    # you can pass the project in as a string.
-    rawStackYaml = builtins.readFile ((src.origSrcSubDir or src) + ("/" + stackYaml));
-
-    # Determine the resolver as it may point to another file we need
-    # to look at.
-    resolver =
-      let
-        rs = pkgs.lib.lists.concatLists (
-          pkgs.lib.lists.filter (l: l != null)
-            (builtins.map (l: builtins.match "^resolver: *(.*)" l)
-              (pkgs.lib.splitString "\n" rawStackYaml)));
-      in
-        pkgs.lib.lists.head (rs ++ [ null ]);
+    inherit (haskellLib.fetchResolver {
+        inherit src stackYaml resolverSha256;
+      }) resolver fetchedResolver;
 
     # Filter just the stack yaml file and any reolver yaml file it points to.
     maybeCleanedSource =
@@ -58,6 +47,9 @@ let
         cp -r "${maybeCleanedSource}/." $TMP
         chmod -R +w $TMP
         substituteInPlace ${stackYaml} --replace "# nix-sha256:" "nix-sha256:"
+        ${pkgs.lib.optionalString (fetchedResolver != null) ''
+          substituteInPlace ${stackYaml} --replace "${resolver}" "${fetchedResolver}"
+        ''}
         stack-repos --stack-yaml ${stackYaml}
         cp repos.json $out
       ''));

overlays/haskell.nix

@@ -260,7 +260,7 @@ final: prev: {
         callStackToNix = import ../lib/call-stack-to-nix.nix {
             pkgs = final.evalPackages.pkgs;
             inherit (final.evalPackages.pkgs) runCommand;
-            inherit (final.evalPackages.haskell-nix) nix-tools mkCacheFile materialize;
+            inherit (final.evalPackages.haskell-nix) nix-tools mkCacheFile materialize haskellLib;
         };
 
         # given a source location call `cabal-to-nix` (from nix-tools) on it

test/default.nix

@@ -159,6 +159,7 @@ let
     builder-haddock = callTest ./builder-haddock {};
     stack-simple = callTest ./stack-simple {};
     stack-local-resolver = callTest ./stack-local-resolver {};
+    stack-remote-resolver = callTest ./stack-remote-resolver {};
     snapshots = callTest ./snapshots {};
     shell-for = callTest ./shell-for {};
     shell-for-setup-deps = callTest ./shell-for-setup-deps {};

test/stack-remote-resolver/.gitignore

@@ -0,0 +1,2 @@
+/.stack-work/
+/*.cabal

test/stack-remote-resolver/default.nix

@@ -0,0 +1,15 @@
+{ project', recurseIntoAttrs, testSrc }:
+
+let
+  project = project' {
+    src = testSrc "stack-remote-resolver";
+    resolverSha256 = "1rldkqqsxd8zxybrkqhc25bcxinhz212kz45jcz8jinfihc91jl7";
+  };
+  packages = project.hsPkgs;
+
+in recurseIntoAttrs {
+  ifdInputs = {
+    inherit (project) stack-nix;
+  };
+  inherit (packages.stack-remote-resolver.components) library;
+}

test/stack-remote-resolver/package.yaml

@@ -0,0 +1,7 @@
+name: stack-remote-resolver
+
+dependencies:
+- base
+
+library:
+  source-dirs: src

test/stack-remote-resolver/src/Lib.hs

@@ -0,0 +1,6 @@
+module Lib
+    ( someFunc
+    ) where
+
+someFunc :: IO ()
+someFunc = putStrLn "someFunc"

test/stack-remote-resolver/stack.yaml

@@ -0,0 +1,4 @@
+resolver: https://raw.githubusercontent.com/input-output-hk/haskell.nix/master/test/stack-local-resolver/snapshot.yaml
+
+packages:
+- .