Major build interface refactor

bin/Snack.hs

@@ -18,6 +18,7 @@ import Control.Monad.IO.Class
 import Data.Aeson (FromJSON, (.:))
 import Data.FileEmbed (embedStringFile)
 import Data.List (intercalate)
+import Data.Maybe (mapMaybe)
 import Data.Semigroup ((<>))
 import Data.String.Interpolate
 import Shelly (Sh)
@@ -283,7 +284,6 @@ newtype ModuleName = ModuleName T.Text
 data BuildResult
   = BuiltLibrary LibraryBuild
   | BuiltExecutable ExecutableBuild
-  | BuiltMulti MultiBuild
   | BuiltGhci GhciBuild
   deriving Show
 
@@ -291,7 +291,6 @@ instance Aeson.FromJSON BuildResult where
     parseJSON v =
       BuiltLibrary <$> (guardBuildType "library" v)
       <|> BuiltExecutable <$> (guardBuildType "executable" v)
-      <|> BuiltMulti <$> (guardBuildType "multi" v)
       <|> BuiltGhci <$> (guardBuildType "ghci" v)
       where
         guardBuildType :: FromJSON a => T.Text -> Aeson.Value -> Aeson.Parser a
@@ -304,10 +303,7 @@ newtype GhciBuild = GhciBuild
   { ghciExePath :: NixPath
   }
     deriving stock Show
-
-instance FromJSON GhciBuild where
-  parseJSON = Aeson.withObject "ghci build" $ \o ->
-    GhciBuild <$> o .: "ghci_path"
+    deriving newtype FromJSON
 
 -- The kinds of builds: library, executable, or a mix of both (currently only
 -- for HPack)
@@ -322,17 +318,6 @@ instance FromJSON ExecutableBuild where
   parseJSON = Aeson.withObject "executable build" $ \o ->
     ExecutableBuild <$> o .: "exe_path"
 
-newtype MultiBuild = MultiBuild
-  { executableBuilds :: Map.Map T.Text ExecutableBuild
-  }
-  deriving stock Show
-
-instance Aeson.FromJSON MultiBuild where
-  parseJSON = Aeson.withObject "multi build" $ \o ->
-    MultiBuild <$> o .: "executables"
-
---- Type-helpers for passing arguments to Nix
-
 data NixArg = NixArg
   { argType :: NixArgType
   , argName :: T.Text
@@ -418,7 +403,7 @@ nixBuild snackCfg extraNixArgs nixExpr =
       : [ argName narg , argValue narg ]
     nixCfg = snackNixCfg snackCfg
 
-snackBuild :: SnackConfig -> PackageFile -> Sh BuildResult
+snackBuild :: SnackConfig -> PackageFile -> Sh [BuildResult]
 snackBuild snackCfg packageFile = do
     NixPath out <- nixBuild snackCfg
       [ NixArg
@@ -441,8 +426,9 @@ snackGhci snackCfg packageFile = do
       ]
       $ NixExpr "snack.inferGhci packageFile"
     liftIO (BS.readFile (T.unpack out)) >>= decodeOrFail >>= \case
-      BuiltGhci g -> pure g
-      b -> throwIO $ userError $ "Expected GHCi build, got " <> show b
+      -- TODO: shouldn't be dropping the tail
+      (BuiltGhci g):_ -> pure g
+      bs -> throwIO $ userError $ "Expected GHCi build, got " <> show bs
 
 runCommand :: SnackConfig -> PackageFile -> Command -> IO ()
 runCommand snackCfg packageFile = \case
@@ -455,13 +441,13 @@ runCommand snackCfg packageFile = \case
 noTest :: IO a
 noTest = fail "There is no test command for test suites"
 
-runBuildResult :: [String] -> BuildResult -> IO ()
-runBuildResult args = \case
-    BuiltExecutable (ExecutableBuild p) -> runExe p args
-    BuiltMulti b
-      | [ExecutableBuild exe] <- Map.elems (executableBuilds b) ->
-          runExe exe args
-    b -> fail $ "Unexpected build type: " <> show b
+runBuildResult :: [String] -> [BuildResult] -> IO ()
+runBuildResult args res =
+    case mapMaybe (\case {BuiltExecutable e -> Just e; _ -> Nothing}) res of
+      [ExecutableBuild p] -> runExe p args
+      -- TODO: be more graceful here
+      -- TODO: allow 'snack run my-exe -- ...'
+      _ -> fail $ "Expected exactly one executable, got: " <> show res
 
 runExe :: NixPath -> [String] -> IO ()
 runExe (NixPath fp) args = executeFile (T.unpack fp) True args Nothing

nix/overlay.nix

@@ -1,5 +1,4 @@
 _: pkgs: rec {
   snack-lib = pkgs.callPackage ../snack-lib/default.nix { };
-  snack-exe =
-    (snack-lib.buildAsExecutable (snack-lib.snackSpec ../bin/package.nix)).out;
+  snack-exe = snack-lib.executable ../bin/package.nix;
 }

snack-lib/default.nix

@@ -19,24 +19,106 @@ with (callPackage ./package-spec.nix {});
 with (callPackage ./hpack.nix {});
 
 let
+
+  # Derivation that creates a binary in a 'bin' folder.
+  executable = packageFile:
+    let
+      specs = specsFromPackageFile packageFile;
+      spec =
+        if pkgs.lib.length specs == 1
+        then pkgs.lib.head specs
+        else abort "'executable' can only be called on a single executable";
+      exe =
+        if spec.packageIsExe
+        then buildAsExecutable spec
+        else abort "'executable' called on a library";
+    in exe.out;
+
+
+  # Build a package spec as resp. a library and an executable
+
+  buildAsLibrary = pkgSpec:
+    buildLibrary ghcWith (libraryModSpecs pkgSpec);
+
+  buildAsExecutable = pkgSpec:
+    let drv = linkMainModule ghcWith (executableMainModSpec pkgSpec);
+    in
+      { out = drv.out;
+        exe_path = "${drv.out}/${drv.relExePath}";
+      };
+
   ghcWith = deps: ghcWithPackages
     (ps: map (p: ps.${p}) deps);
 
-  # Assumes the package description describes an executable
-  withMainModSpec = pkgDescr: act:
+  specsFromPackageFile = packageFile:
     let
-      mainModName = pkgDescr.packageMain;
-      mainModSpec =
+      basename = builtins.baseNameOf packageFile;
+      components = pkgs.lib.strings.splitString "." basename;
+      ext =
+        if pkgs.lib.length components <= 1
+        then abort ("File " ++ packageFile ++ " does not have an extension")
+        else pkgs.lib.last components;
+      fromNix = [(mkPackageSpec (import packageFile))];
+      fromHPack =
         let
-          fld = moduleSpecFold' modSpecs;
-          modSpecs = foldDAG fld [mainModName];
-        in modSpecs.${mainModName};
-      drv = linkMainModule ghcWith mainModSpec;
-    in
-      { out = drv.out;
-        outPath = "${drv.out}";
-        exePath = "${drv.out}/${drv.relExePath}";
-      };
+          descrs = pkgDescrsFromHPack packageFile;
+          executables =
+            builtins.map mkPackageSpec descrs.executables;
+          library = withAttr descrs "library" null
+              (comp: if builtins.isNull comp then null else mkPackageSpec comp);
+        in executables ++ (if builtins.isNull library then [] else [ library ]);
+      specs =
+        if ext == "nix" then fromNix
+        else if ext == "yaml" then fromHPack
+        else if ext == "yml" then fromHPack
+        else abort ("Unknown extension " ++ ext ++ " of file " ++ packageFile);
+    in specs;
+
+  # Normal build (libs, exes)
+
+  inferBuild = packageFile:
+    mkPackages (specsFromPackageFile packageFile);
+
+  mkPackages = pkgSpecs: writeText "build.json"
+    ( builtins.toJSON
+      ( builtins.map
+          (pkgSpec:
+            if pkgSpec.packageIsExe
+            then
+              { build_type = "executable";
+                result = buildAsExecutable pkgSpec;
+              }
+            else
+              { build_type = "library";
+                result = buildAsLibrary pkgSpec;
+              }
+          ) pkgSpecs
+      )
+    );
+
+  # GHCi build (libs, exes)
+
+  inferGhci = packageFile:
+    mkPackagesGhci (specsFromPackageFile packageFile);
+
+  mkPackagesGhci = pkgSpecs: writeText "hpack-ghci-json"
+    ( builtins.toJSON (
+        builtins.map
+          (pkgSpec:
+            let
+              drv =
+                if pkgSpec.packageIsExe
+                then ghciWithMain ghcWith (executableMainModSpec pkgSpec)
+                else ghciWithModules ghcWith (libraryModSpecs pkgSpec)
+                ;
+            in
+            { build_type = "ghci"; # TODO: need to record the name somewhere
+              result = "${drv.out}/bin/ghci-with-files";
+              }
+          ) pkgSpecs
+    ));
+
+  # How to build resp. libraries and executables
 
   libraryModSpecs = pkgSpec:
     let
@@ -58,143 +140,13 @@ let
         in modSpecs.${mainModName};
     in mainModSpec;
 
-  buildAsLibrary = pkgSpec:
-    buildLibrary ghcWith (libraryModSpecs pkgSpec);
-
-  buildAsExecutable = pkgSpec:
-    let drv = linkMainModule ghcWith (executableMainModSpec pkgSpec);
-    in
-      { out = drv.out;
-        exe_path = "${drv.out}/${drv.relExePath}";
-      };
-
-  # TODO: deduplicate extensions + update README with --package-file
-  inferBuild = packageFile:
-    let
-      basename = builtins.baseNameOf packageFile;
-      components = pkgs.lib.strings.splitString "." basename;
-      ext =
-        if pkgs.lib.length components <= 1
-        then abort ("File " ++ packageFile ++ " does not have an extension")
-        else pkgs.lib.last components;
-      build =
-        if ext == "nix" then inferSnackBuild
-        else if ext == "yaml" then inferHPackBuild
-        else if ext == "yml" then inferHPackBuild
-        else abort ("Unknown extension " ++ ext ++ " of file " ++ packageFile);
-    in build packageFile;
-
-  inferGhci = packageFile:
-    let
-      basename = builtins.baseNameOf packageFile;
-      components = pkgs.lib.strings.splitString "." basename;
-      ext =
-        if pkgs.lib.length components <= 1
-        then abort ("File " ++ packageFile ++ " does not have an extension")
-        else pkgs.lib.last components;
-      ghci =
-        if ext == "nix" then inferSnackGhci
-        else if ext == "yaml" then inferHPackGhci
-        else if ext == "yml" then inferHPackGhci
-        else abort ("Unknown extension " ++ ext ++ " of file " ++ packageFile);
-    in ghci packageFile;
-
-  inferSnackBuild = packageNix: mkPackage (import packageNix);
-
-  inferSnackGhci = packageNix: writeText "snack-ghci-json"
-    ( builtins.toJSON (
-    let
-      pkgSpec = mkPackageSpec (import packageNix);
-      drv =
-        if builtins.isNull pkgSpec.packageMain
-        then ghciWithModules ghcWith (libraryModSpecs pkgSpec)
-        else ghciWithMain ghcWith (executableMainModSpec pkgSpec);
-    in
-      { build_type = "ghci";
-        result = {
-            "ghci_path" = "${drv.out}/bin/ghci-with-files";
-          };
-      }
-    ));
-
-  inferHPackBuild = packageYaml: writeText "hpack-build-json"
-    ( builtins.toJSON (
-    let pkgSpecs = hpackSpecs packageYaml;
-    in
-      { build_type = "multi";
-        result =
-          { library =
-              if builtins.isNull pkgSpecs.library
-              then null
-              else buildAsLibrary (pkgSpecs.library);
-            executables = lib.attrsets.mapAttrs (k: v: buildAsExecutable v) pkgSpecs.executables;
-          };
-      }
-    ));
-
-  inferHPackGhci = packageYaml: writeText "hpack-ghci-json"
-    ( builtins.toJSON (
-    let
-      pkgSpecs = hpackSpecs packageYaml;
-      pkgSpec = mkPackageSpec (import packageNix);
-      drv =
-        let exeSpecs = builtins.attrValues pkgSpecs.executables;
-        in
-          if lib.lists.length exeSpecs == 1
-          then ghciWithMain ghcWith (executableMainModSpec (lib.lists.head exeSpecs))
-          else
-            if builtins.isNull pkgSpecs.library
-            then abort "GHCi: needs either a single executable or a library"
-            else ghciWithModules ghcWith (libraryModSpecs pkgSpecs.library);
-    in
-      { build_type = "ghci";
-        result = {
-            "ghci_path" = "${drv.out}/bin/ghci-with-files";
-          };
-      }
-    ));
-
-  snackSpec = packageNix: mkPackageSpec (import packageNix);
-  hpackSpecs = packageYaml:
-    let
-      descrs = pkgDescrsFromHPack packageYaml;
-    in
-      { library = withAttr descrs "library" null
-          (comp: if builtins.isNull comp then null else mkPackageSpec comp);
-        executables =
-          lib.attrsets.mapAttrs (k: v: mkPackageSpec v) descrs.executables;
-      };
-
-  mkPackage = snackNixExpr: writeText "snack-build-json"
-    ( builtins.toJSON (
-    let
-      pkgSpec = mkPackageSpec snackNixExpr;
-    in
-      if builtins.isNull pkgSpec.packageMain
-      then
-        { "build_type" = "library";
-          "result" = buildAsLibrary pkgSpec;
-        }
-      else
-        { "build_type" = "executable";
-          "result" = buildAsExecutable pkgSpec;
-        }
-    ));
-
 in
   {
     inherit
     inferBuild
     inferGhci
-    inferSnackBuild
-    inferSnackGhci
-    inferHPackBuild
-    inferHPackGhci
-    packageYaml
     buildAsExecutable
     buildAsLibrary
-    snackSpec
-    hpackSpecs
-    mkPackage
+    executable
     ;
   }

snack-lib/hpack.nix

@@ -52,9 +52,9 @@ in
           );
 
         exes =
-          withAttr package "executables" {} (lib.mapAttrs (k: v: mkExe v)) //
-          withAttr package "executable" {} (comp: { ${package.name} = mkExe comp; });
-        mkExe = component:
+          withAttr package "executables" [] (lib.mapAttrsToList (k: v: mkExe k v)) ++
+          withAttr package "executable" [] (comp: [(mkExe package.name comp)] );
+        mkExe = nn: component:
           let
             depOrPack =
               lib.lists.partition
@@ -62,8 +62,9 @@ in
                 (optAttr component "dependencies" []);
           in
             { main = fileToModule component.main;
+              name = nn;
               src =
-                let 
+                let
                   base = builtins.dirOf packageYaml;
                   source-dirs = optAttr component "source-dirs" ".";
                 in

snack-lib/package-spec.nix

@@ -8,7 +8,8 @@ rec {
 
   mkPackageSpec =
   packageDescr@
-    { src
+    { src ? []
+    , name ? null
     , main ? null
     , ghcOpts ? []
     , dependencies ? []
@@ -17,7 +18,9 @@ rec {
     , extra-directories ? []
     , packages ? []
     }:
-    { packageMain = main;
+    { packageIsExe = ! builtins.isNull main;
+      packageName = name;
+      packageMain = main;
       packageSourceDirs =
         if builtins.isList src
         then src

tests/library-2/test

@@ -6,7 +6,7 @@ set -euo pipefail
 test() {
   TMP_FILE=$(mktemp)
 
-  cat $($SNACK build) | jq -M '.result | keys' > $TMP_FILE
+  cat $($SNACK build) | jq -M '.[0] | .result | keys' > $TMP_FILE
 
   diff golden.jq $TMP_FILE
 

tests/library-3/test

@@ -6,7 +6,7 @@ set -euo pipefail
 test() {
   TMP_FILE=$(mktemp)
 
-  cat $($SNACK build) | jq -M '.result | keys' > $TMP_FILE
+  cat $($SNACK build) | jq -M '.[0] | .result | keys' > $TMP_FILE
 
   diff golden.jq $TMP_FILE
 

tests/swp/test

@@ -6,7 +6,7 @@ set -euo pipefail
 test() {
   TMP_FILE=$(mktemp)
 
-  cat $($SNACK build) | jq -M '.result | keys' > $TMP_FILE
+  cat $($SNACK build) | jq -M '.[0] | .result | keys' > $TMP_FILE
 
   diff golden.jq $TMP_FILE
 }

tests/trans-imp/test

@@ -6,7 +6,7 @@ set -euo pipefail
 test() {
   TMP_FILE=$(mktemp)
 
-  cat $($SNACK build) | jq -M '.result | keys' > $TMP_FILE
+  cat $($SNACK build) | jq -M '.[0] | .result | keys' > $TMP_FILE
 
   diff golden.jq $TMP_FILE