Add --print-type to exe:dhall-to-cabal

See #22

dhall-to-cabal.cabal

@@ -5,7 +5,6 @@ build-type: Simple
 license: MIT
 homepage: https://github.com/ocharles/dhall-to-cabal
 bug-reports: https://github.com/ocharles/dhall-to-cabal/issues
-tested-with: GHC ==8.2.2 GHC ==8.4.1
 
 source-repository head
     type: git
@@ -15,16 +14,16 @@ library
     exposed-modules:
         Distribution.Package.Dhall
     build-depends:
-        base ^>=4.10,
         Cabal ^>=2.0,
-        dhall ^>=1.9,
-        text ^>=1.2,
+        base ^>=4.10,
         bytestring ^>=0.10,
         containers ^>=0.5,
-        vector ^>=0.12,
-        trifecta ^>=1.7,
+        dhall ^>=1.9,
+        text ^>=1.2,
         text-format ^>=0.3,
-        transformers ^>=0.5.2
+        transformers ^>=0.5.2,
+        trifecta ^>=1.7,
+        vector ^>=0.12
     other-extensions: ApplicativeDo GADTs GeneralizedNewtypeDeriving
                       LambdaCase OverloadedStrings RecordWildCards TypeApplications
     hs-source-dirs: lib
@@ -36,27 +35,28 @@ executable  dhall-to-cabal
     main-is: Main.hs
     scope: public
     build-depends:
+        Cabal ^>=2.0,
         base ^>=4.10,
+        dhall ^>=1.9,
         dhall-to-cabal -any,
         optparse-applicative ^>=0.13.2 || ^>=0.14,
-        text ^>=1.2,
-        dhall ^>=1.9,
-        Cabal ^>=2.0
+        prettyprinter ^>=1.1.1,
+        text ^>=1.2
     other-extensions: NamedFieldPuns
     hs-source-dirs: exe
 
 test-suite  golden-tests
     type: exitcode-stdio-1.0
     main-is: GoldenTests.hs
     build-depends:
-        bytestring ^>=0.10,
         base ^>=4.10,
         Cabal ^>=2.0,
-        text ^>=1.2,
-        tasty ^>=0.11,
-        filepath ^>=1.4,
+        Diff ^>=0.3.4,
+        bytestring ^>=0.10,
         dhall-to-cabal -any,
+        filepath ^>=1.4,
+        tasty ^>=0.11,
         tasty-golden ^>=2.3,
-        Diff ^>=0.3.4
+        text ^>=1.2
     hs-source-dirs: golden-tests
 

dhall-to-cabal.dhall

@@ -47,6 +47,8 @@ in  let deps =
                 (majorBoundVersion (v "0.13.2"))
                 (majorBoundVersion (v "0.14"))
               )
+          , prettyprinter =
+              package "prettyprinter" (majorBoundVersion (v "1.1.1"))
           , tasty =
               package "tasty" (majorBoundVersion (v "0.11"))
           , tasty-golden =
@@ -113,6 +115,7 @@ in    gitHub-project { owner = "ocharles", repo = "dhall-to-cabal" }
                     , deps.dhall
                     , deps.dhall-to-cabal
                     , deps.optparse-applicative
+                    , deps.prettyprinter
                     , deps.text
                     ]
                 , hs-source-dirs =

exe/Main.hs

@@ -2,40 +2,95 @@
 
 module Main (main) where
 
+import Data.Foldable ( asum )
 import Data.Function ( (&) )
 import System.Environment ( getArgs )
 
 import Distribution.Package.Dhall
 
 import qualified Data.Text.Lazy.IO as LazyText
+import qualified Data.Text.Prettyprint.Doc as Pretty
+import qualified Data.Text.Prettyprint.Doc.Render.Text as Pretty
 import qualified Dhall
 import qualified Distribution.PackageDescription.PrettyPrint as Cabal
 import qualified Options.Applicative as OptParse
+import qualified System.IO
 
 
 
-data Options = Options { dhallFilePath :: String }
+data Command
+  = RunDhallToCabal DhallToCabalOptions
+  | PrintType
 
 
 
-run :: Options -> IO ()
-run Options { dhallFilePath } =
+data DhallToCabalOptions = DhallToCabalOptions
+  { dhallFilePath :: String }
+
+
+
+dhallToCabalOptionsParser :: OptParse.Parser DhallToCabalOptions
+dhallToCabalOptionsParser =
+  DhallToCabalOptions
+    <$> OptParse.argument
+          OptParse.str ( OptParse.metavar "<dhall input file>" )
+
+
+
+printTypeParser :: OptParse.Parser ()
+printTypeParser =
+  OptParse.flag' () ( OptParse.long "print-type" )
+
+
+
+runDhallToCabal :: DhallToCabalOptions -> IO ()
+runDhallToCabal DhallToCabalOptions { dhallFilePath } =
   dhallFileToCabal dhallFilePath
     & fmap Cabal.showGenericPackageDescription
     >>= putStrLn
 
 
 
 main :: IO ()
-main =
-  OptParse.execParser opts >>= run
+main = do
+  command <-
+    OptParse.execParser opts
+
+  case command of
+    RunDhallToCabal options ->
+      runDhallToCabal options
+
+    PrintType ->
+      printType
 
   where
 
   parser =
-    Options
-      <$> OptParse.argument
-            OptParse.str ( OptParse.metavar "<dhall input file>" )
+    asum
+      [ RunDhallToCabal <$> dhallToCabalOptionsParser
+      , PrintType <$ printTypeParser
+      ]
 
   opts =
     OptParse.info parser mempty
+
+
+
+-- Shamelessly taken from dhall-format
+
+opts :: Pretty.LayoutOptions
+opts =
+  Pretty.defaultLayoutOptions
+    { Pretty.layoutPageWidth = Pretty.AvailablePerLine 80 1.0 }
+
+
+
+printType :: IO ()
+printType = do
+  Pretty.renderIO
+    System.IO.stdout
+    ( Pretty.layoutSmart opts
+        ( Pretty.pretty ( Dhall.expected genericPackageDescription ) )
+    )
+
+  putStrLn ""