lib: outputFileFromOpts now returns a maybe; cleanups

hledger/Hledger/Cli/CliOptions.hs

@@ -555,17 +555,19 @@ expandPathPreservingPrefix d prefixedf = do
     Just p  -> p ++ ":" ++ f'
     Nothing -> f'
 
--- | Get the expanded, absolute output file path from options,
--- or the default (-, meaning stdout).
-outputFileFromOpts :: CliOpts -> IO FilePath
+-- | Get the expanded, absolute output file path specified by an
+-- -o/--output-file options, or nothing, meaning stdout.
+outputFileFromOpts :: CliOpts -> IO (Maybe FilePath)
 outputFileFromOpts opts = do
   d <- getCurrentDirectory
   case output_file_ opts of
-    Just p  -> expandPath d p
-    Nothing -> return "-"
+    Nothing -> return Nothing
+    Just f  -> Just <$> expandPath d f
 
+defaultOutputFormat :: String
 defaultOutputFormat = "txt"
 
+outputFormats :: [String]
 outputFormats =
   [defaultOutputFormat] ++
   ["csv"

hledger/Hledger/Cli/Utils.hs

@@ -161,7 +161,7 @@ journalAddForecast CliOpts{inputopts_=iopts, reportspec_=rspec} j =
 writeOutput :: CliOpts -> String -> IO ()
 writeOutput opts s = do
   f <- outputFileFromOpts opts
-  (if f == "-" then putStr else writeFile f) s
+  (maybe putStr writeFile f) s
 
 -- | Write some output to stdout or to a file selected by --output-file.
 -- If the file exists it will be overwritten. This function operates on Lazy
@@ -169,7 +169,7 @@ writeOutput opts s = do
 writeOutputLazyText :: CliOpts -> TL.Text -> IO ()
 writeOutputLazyText opts s = do
   f <- outputFileFromOpts opts
-  (if f == "-" then TL.putStr else TL.writeFile f) s
+  (maybe TL.putStr TL.writeFile f) s
 
 -- -- | Get a journal from the given string and options, or throw an error.
 -- readJournal :: CliOpts -> String -> IO Journal