Don't use absolute paths for executables (#639)

Author: f-f

package.yaml

@@ -83,7 +83,7 @@ library:
   - bytestring
   - Cabal
   - containers
-  - dhall >= 1.29.0
+  - dhall >= 1.31.1
   - directory >= 1.3.4.0
   - either
   - exceptions
@@ -104,7 +104,7 @@ library:
   - prettyprinter
   - process
   - retry
-  - rio
+  - rio >= 0.1.13.0
   - rio-orphans
   - safe
   - semver-range

src/Spago/Prelude.hs

@@ -228,6 +228,9 @@ pretty = PrettyText.renderStrict
 --   or die trying
 findExecutableOrDie :: HasLogFunc env => String -> RIO env Text
 findExecutableOrDie cmd = do
-  Directory.findExecutable cmd >>= \case 
+  Directory.findExecutable cmd >>= \case
     Nothing -> die [ "Executable was not found in path: " <> displayShow cmd ]
-    Just path -> pure $ Text.pack path
+    -- Note: we ignore the path and just return the input because the one we get
+    -- here is absolute, and Windows doesn't seem to be able to deal with that.
+    -- See: https://github.com/purescript/spago/issues/635
+    Just _path -> pure $ Text.pack cmd

src/Spago/RunEnv.hs

@@ -3,6 +3,7 @@ module Spago.RunEnv where
 import Spago.Prelude
 import Spago.Env
 
+import qualified Data.Text as Text
 import qualified System.Environment  as Env
 import qualified Distribution.System as OS
 import qualified Turtle
@@ -120,14 +121,13 @@ getPurs usePsa = do
     UsePsa -> findExecutable "psa" >>= \case
       Just _  -> pure "psa"
       Nothing -> pure "purs"
-  try (findExecutableOrDie pursCandidate) >>= \case
-    Right p -> pure p
-    -- one last try for Windows
-    Left (err :: SomeException) -> case OS.buildOS of
-      OS.Windows -> do
-        logDebug $ displayShow err
-        findExecutableOrDie (pursCandidate <> ".cmd")
-      _ -> throwIO err
+  -- We first try this for Windows
+  case OS.buildOS of
+    OS.Windows -> do
+      findExecutable (pursCandidate <> ".cmd") >>= \case
+        Just _ -> pure (Text.pack pursCandidate <> ".cmd")
+        Nothing -> findExecutableOrDie pursCandidate
+    _ -> findExecutableOrDie pursCandidate
 
 getPackageSet :: (HasLogFunc env, HasConfigPath env) => RIO env PackageSet
 getPackageSet = do