Use num of cores as jobs by default

bin/Snack.hs

@@ -171,18 +171,28 @@ discoverPackageFile = do
 
 -- | How to call @nix-build@
 newtype NixConfig = NixConfig
-  { nixNJobs :: Int }
+  { nixNJobs :: NJobs }
+
+data NJobs = NJobs Int | NJobsAuto
+
+nJobsValue :: NJobs -> String
+nJobsValue = \case
+  NJobs n -> show n
+  NJobsAuto -> "auto"
 
 parseNixConfig :: Opts.Parser NixConfig
 parseNixConfig =
-    (NixConfig <$>
-        Opts.option Opts.auto
+    NixConfig <$>
+    (
+      (NJobs <$> Opts.option Opts.auto
         (Opts.long "jobs"
         <> Opts.short 'j'
-        <> Opts.value 1
         <> Opts.metavar "INT"
-        <> Opts.help "How many jobs to run concurrently")
-        )
+        <> Opts.help "How many jobs to run concurrently (default: number of available cores)")
+        ) <|>
+      pure NJobsAuto
+    )
+
 
 --- Snack configuration (unrelated to packages)
 
@@ -391,7 +401,7 @@ nixBuild snackCfg extraNixArgs nixExpr =
       [ "-" -- read expression from stdin
       , "--no-out-link" -- no need for roots
       -- how many jobs to run concurrently (-j)
-      , "--max-jobs", T.pack (show (nixNJobs nixCfg))
+      , "--max-jobs", T.pack (nJobsValue (nixNJobs nixCfg))
       ] <> (concatMap toCliArgs nixArgs)
     funArgs :: [String]
     funArgs = toFunArg <$> nixArgs

tests/any-paths/test

@@ -8,6 +8,6 @@ test() {
   $SNACK run
 }
 
-SNACK="snack -j4 --package-file ./package.nix" test
-SNACK="snack -j4 --package-file ./package.nix -l ../../snack-lib" test
-SNACK="snack -j4 --package-file ./package.yaml" test
+SNACK="snack --package-file ./package.nix" test
+SNACK="snack --package-file ./package.nix -l ../../snack-lib" test
+SNACK="snack --package-file ./package.yaml" test

tests/cpp-2/test

@@ -15,4 +15,4 @@ test() {
   rm $TMP_FILE
 }
 
-SNACK="snack -j4" test
+SNACK="snack" test

tests/cpp/test

@@ -15,4 +15,4 @@ test() {
   rm $TMP_FILE
 }
 
-SNACK="snack -j4" test
+SNACK="snack" test

tests/extended-config/test

@@ -16,5 +16,5 @@ test() {
   rm $TMP_FILE
 }
 
-SNACK="snack -j4 --snack-nix snack.nix --package-file package.yaml" test
-SNACK="snack -j4" test
+SNACK="snack --snack-nix snack.nix --package-file package.yaml" test
+SNACK="snack" test

tests/extensions/test

@@ -15,6 +15,6 @@ test() {
   rm $TMP_FILE
 }
 
-SNACK="snack -j4 --package-file ./package.nix" test
-SNACK="snack -j4 --package-file ./package.nix -l ../../snack-lib" test
-SNACK="snack -j4 --package-file ./package.yaml" test
+SNACK="snack --package-file ./package.nix" test
+SNACK="snack --package-file ./package.nix -l ../../snack-lib" test
+SNACK="snack --package-file ./package.yaml" test

tests/hpack/test

@@ -9,7 +9,7 @@ git clone http://github.com/nmattia/pboy.git $TMP_DIR
 git -C $TMP_DIR reset --hard a2458d6984930a33a3b1972cb6d5c167d2511b06
 
 pushd $TMP_DIR
-snack -j4 build
+snack build
 popd
 
 rm -rf $TMP_DIR

tests/library-2/test

@@ -15,7 +15,7 @@ test() {
   rm $TMP_FILE
 }
 
-SNACK="snack -j4" test
-SNACK="snack -j4 --package-file ./package.nix" test
-SNACK="snack -j4 --package-file ./package.nix -l ../../snack-lib" test
+SNACK="snack" test
+SNACK="snack --package-file ./package.nix" test
+SNACK="snack --package-file ./package.nix -l ../../snack-lib" test
 # Note: no HPack test, because HPack doesn't support multi library

tests/library-3/test

@@ -17,5 +17,5 @@ test() {
 
 SNACK="snack" test
 SNACK="snack --package-file ./package.nix" test
-SNACK="snack -j4 --package-file ./package.nix -l ../../snack-lib" test
+SNACK="snack --package-file ./package.nix -l ../../snack-lib" test
 # Note: no HPack test, because HPack doesn't support multi library

tests/library/test

@@ -15,5 +15,5 @@ test() {
   rm $TMP_FILE
 }
 
-SNACK="snack -j4 --package-file ./package.nix" test
-SNACK="snack -j4 --package-file ./package.yaml" test
+SNACK="snack --package-file ./package.nix" test
+SNACK="snack --package-file ./package.yaml" test

tests/magichash/test

@@ -15,5 +15,5 @@ test() {
   rm $TMP_FILE
 }
 
-SNACK="snack -j4 --package-file ./package.nix" test
-SNACK="snack -j4 --package-file ./package.yaml" test
+SNACK="snack --package-file ./package.nix" test
+SNACK="snack --package-file ./package.yaml" test

tests/nested/test

@@ -16,5 +16,5 @@ test() {
   rm $TMP_FILE
 }
 
-SNACK="snack -j4 --package-file ./package.nix" test
-SNACK="snack -j4 --package-file ./package.yaml" test
+SNACK="snack --package-file ./package.nix" test
+SNACK="snack --package-file ./package.yaml" test

tests/packages/test

@@ -16,5 +16,5 @@ test() {
   rm $TMP_FILE
 }
 
-SNACK="snack -j4 --package-file ./package.nix" test
-SNACK="snack -j4 --package-file ./package.yaml" test
+SNACK="snack --package-file ./package.nix" test
+SNACK="snack --package-file ./package.yaml" test

tests/readme/test

@@ -8,6 +8,6 @@ test() {
   $SNACK run
 }
 
-SNACK="snack -j4 --package-file ./package.nix" test
-SNACK="snack -j4 --package-file ./package.nix -l ../../snack-lib" test
-SNACK="snack -j4 --package-file ./package.yaml" test
+SNACK="snack --package-file ./package.nix" test
+SNACK="snack --package-file ./package.nix -l ../../snack-lib" test
+SNACK="snack --package-file ./package.yaml" test

tests/run-args/test

@@ -8,4 +8,4 @@ test() {
   $SNACK run -- hello 'this is' 'the answer' bye | diff golden -
 }
 
-SNACK="snack -j4" test
+SNACK="snack" test

tests/single-main/test

@@ -8,4 +8,4 @@ test() {
   $SNACK run
 }
 
-SNACK="snack -j4" test
+SNACK="snack" test

tests/source-dirs/test

@@ -16,5 +16,5 @@ test() {
 }
 
 
-SNACK="snack -j4 -p ./package.nix" test
-SNACK="snack -j4 -p ./package.yaml" test
+SNACK="snack -p ./package.nix" test
+SNACK="snack -p ./package.yaml" test

tests/strips-versions/test

@@ -15,5 +15,5 @@ test() {
   rm $TMP_FILE
 }
 
-SNACK="snack -j4 --package-file ./package.nix" test
-SNACK="snack -j4 --package-file ./package.yaml" test
+SNACK="snack --package-file ./package.nix" test
+SNACK="snack --package-file ./package.yaml" test

tests/swp/test

@@ -11,4 +11,4 @@ test() {
   diff golden.jq $TMP_FILE
 }
 
-SNACK="snack -j4" test
+SNACK="snack" test

tests/template-haskell-2/test

@@ -3,12 +3,12 @@
 
 set -euo pipefail
 
-snack -j4 build --package-file code/package.nix
-snack -j4 run --package-file code/package.nix | diff golden -
+snack build --package-file code/package.nix
+snack run --package-file code/package.nix | diff golden -
 
 TMP_FILE=$(mktemp)
 
-capture_io "$TMP_FILE" main | snack -j4 --package-file code/package.nix ghci
+capture_io "$TMP_FILE" main | snack --package-file code/package.nix ghci
 
 diff golden $TMP_FILE
 rm $TMP_FILE

tests/template-haskell-3/test

@@ -3,12 +3,12 @@
 
 set -euo pipefail
 
-snack -j4 build
-snack -j4 run | diff golden -
+snack build
+snack run | diff golden -
 
 TMP_FILE=$(mktemp)
 
-capture_io "$TMP_FILE" main | snack -j4 ghci
+capture_io "$TMP_FILE" main | snack ghci
 
 diff golden $TMP_FILE
 rm $TMP_FILE

tests/template-haskell-4/test

@@ -3,12 +3,12 @@
 
 set -euo pipefail
 
-snack -j4 build
-snack -j4 run | diff golden -
+snack build
+snack run | diff golden -
 
 TMP_FILE=$(mktemp)
 
-capture_io "$TMP_FILE" main | snack -j4 ghci
+capture_io "$TMP_FILE" main | snack ghci
 
 diff golden $TMP_FILE
 rm $TMP_FILE

tests/template-haskell/test

@@ -3,12 +3,12 @@
 
 set -euo pipefail
 
-snack -j4 build
-snack -j4 run | diff golden -
+snack build
+snack run | diff golden -
 
 TMP_FILE=$(mktemp)
 
-capture_io "$TMP_FILE" main | snack -j4 ghci
+capture_io "$TMP_FILE" main | snack ghci
 
 diff golden $TMP_FILE
 rm $TMP_FILE

tests/trans-imp/test

@@ -15,6 +15,6 @@ test() {
   rm $TMP_FILE
 }
 
-SNACK="snack -j4" test
-SNACK="snack -j4 --package-file ./package.nix" test
+SNACK="snack" test
+SNACK="snack --package-file ./package.nix" test
 # Note: no HPack test, because HPack doesn't support multi library