System.Directory.listDir

This function is what users want 99.9% of time.

libs/base/System/Directory.idr

@@ -118,3 +118,20 @@ dirEntry d = do r <- nextDirEntry d
                          Left e         => Left e
                          Right (Just n) => Right n
                          Right Nothing  => Left FileNotFound
+
+collectDir : HasIO io => Directory -> io (Either FileError (List String))
+collectDir d
+    = liftIO $ do let (>>=) : (IO . Either e) a -> (a -> (IO . Either e) b) -> (IO . Either e) b
+                      (>>=) = Prelude.(>>=) @{Monad.Compose {m = IO} {t = Either e}}
+                  Just n <- nextDirEntry d
+                    | Nothing => pure $ Right []
+                  ns <- assert_total $ collectDir d
+                  pure $ Right (n :: ns)
+
+export
+listDir : HasIO io => String -> io (Either FileError (List String))
+listDir name = do Right d <- openDir name
+                    | Left e => pure $ Left e
+                  ns <- collectDir d
+                  ignore <- closeDir d
+                  pure $ ns

tests/base/system_directory/ReadDir.idr

@@ -5,16 +5,8 @@ panic : String -> IO a
 panic s = do putStrLn s
              exitFailure
 
-collectEntries : Directory -> IO (List String)
-collectEntries d = do Right (Just n) <- nextDirEntry d
-                        | Right Nothing => pure []
-                        | Left e        => panic (show e)
-                      ns <- collectEntries d
-                      pure (n :: ns)
-
 main : IO ()
-main = do Right d <- openDir "dir"
+main = do Right ["a"] <- listDir "dir"
             | Left e => panic (show e)
-          ["a"] <- collectEntries d
-            | x => panic ("wrong entries: " ++ (show x))
+            | Right x => panic ("wrong entries: " ++ (show x))
           pure ()