it works

app/Main.hs

@@ -1,17 +1,26 @@
+{-# LANGUAGE MultiWayIf #-}
+
 module Main where
 
+import Control.Monad
 import Data.Attoparsec.Text
+import qualified Data.Text as T
 import qualified Data.Text.IO as T
 import Hie.Cabal.Parser
 import Hie.Yaml
-import System.Environment
+import System.Directory
+import System.FilePath.Posix
 
 main :: IO ()
 main = do
-  args <- getArgs
-  file <- T.readFile $ head args
+  files <- listDirectory =<< getCurrentDirectory
+  let path = filter ((".cabal" ==) . takeExtension) files
+      sOrC =
+        if  | any ((".stack-work" ==) . takeFileName) files -> stackHieYaml
+            | any (("dist-newstyle" ==) . takeFileName) files -> cabalHieYaml
+            | otherwise -> stackHieYaml
+  when (null path) $ error "No .cabal file found!\n You may need to run stack build."
+  file <- T.readFile $ head path
   case parseOnly parseSec file of
-    Right r -> do
-      T.putStr $ cabalHieYaml r
-      T.putStr $ stackHieYaml r
+    Right r -> T.writeFile "hie.yaml" $ sOrC r
     _ -> error "Could not parse *.cabal file"

hie.yaml

@@ -1,8 +1,8 @@
 cradle:
   stack:
-      - path: ./src
-        component: "implicit-hie:lib"
-      - path: ./app
-        component: "implicit-hie:exe:implicit-hie-exe"
-      - path: ./test
-        component: "implicit-hie:test:implicit-hie-test"
+    - path: "src"
+      component: "implicit-hie:lib"
+    - path: "app"
+      component: "implicit-hie:exe:implicit-hie-exe"
+    - path: "test"
+      component: "implicit-hie:test:implicit-hie-test"

implicit-hie.cabal

@@ -4,7 +4,7 @@ cabal-version: 1.12
 --
 -- see: https://github.com/sol/hpack
 --
--- hash: bc348cef928e75313b689d7626632633e11398ad278358aea4933e83a9564985
+-- hash: f941332727b491b78a5ecc8465f43d3597766e4d3363a1d76d459e4a84515b5f
 
 name:           implicit-hie
 version:        0.1.0.0
@@ -51,6 +51,8 @@ executable implicit-hie-exe
   build-depends:
       attoparsec
     , base >=4.7 && <5
+    , directory
+    , filepath
     , implicit-hie
     , text
     , yaml

package.yaml

@@ -51,6 +51,8 @@ executables:
     - -with-rtsopts=-N
     dependencies:
     - implicit-hie
+    - directory
+    - filepath
 
 tests:
   implicit-hie-test:

src/Hie/Yaml.hs

@@ -29,8 +29,8 @@ cabalComponent _ (Test p cn) = component p $ "test:" <> cn
 
 stackComponent :: Name -> Component -> T.Text
 stackComponent n (Lib p) = component p $ n <> ":lib"
-stackComponent n (Exe p cn) = component p $ n <> ":exe:" <> cn
-stackComponent n (Test p cn) = component p $ n <> ":test:" <> cn
+stackComponent n (Exe cn p) = component p $ n <> ":exe:" <> cn
+stackComponent n (Test cn p) = component p $ n <> ":test:" <> cn
 
 component :: T.Text -> T.Text -> T.Text
 component p c =

test/Spec.hs

@@ -1,8 +1,10 @@
 {-# LANGUAGE OverloadedStrings #-}
 
+import Data.Attoparsec.Text
 import qualified Data.Text as T
 import Data.Text (Text)
 import Hie.Cabal.Parser
+import Hie.Yaml
 import Test.Hspec
 import Test.Hspec.Attoparsec
 
@@ -25,20 +27,25 @@ spec = do
       `shouldParse` Lib "src"
   describe "Should Succeed"
     $ it "successfully parses library section"
-    $ ("name: implicit-hie\n" <> exeSection <> testSection <> libSection)
-      ~> parseSec
-        `shouldParse` Package
-          "implicit-hie"
-          [ Exe "implicit-hie-exe" "app",
-            Test "implicit-hie-test" "test",
-            Lib "src"
-          ]
+    $ fullFile ~> parseSec
+      `shouldParse` Package
+        "implicit-hie"
+        [ Lib "src",
+          Exe "implicit-hie-exe" "app",
+          Test "implicit-hie-test" "test"
+        ]
   describe "Should Succeed"
     $ it
       "successfully parses library section"
     $ let r = "test\n"
        in (libSection <> r) ~?> parseLib 0
             `leavesUnconsumed` r
+  describe "Should Succeed"
+    $ it "successfully generates stack hie.yaml"
+    $ (stackHieYaml <$> parseOnly parseSec fullFile) `shouldBe` Right stackHie
+
+fullFile :: Text
+fullFile = "name: implicit-hie\n" <> libSection <> exeSection <> testSection
 
 exeSection :: Text
 exeSection =
@@ -85,3 +92,15 @@ libSection =
   \  , text\n\
   \  default-language: Haskell2010\n\
   \"
+
+stackHie :: Text
+stackHie =
+  "cradle:\n\
+  \  stack:\n\
+  \    - path: \"src\"\n\
+  \      component: \"implicit-hie:lib\"\n\
+  \    - path: \"app\"\n\
+  \      component: \"implicit-hie:exe:implicit-hie-exe\"\n\
+  \    - path: \"test\"\n\
+  \      component: \"implicit-hie:test:implicit-hie-test\"\n\
+  \"