From: Cameron Ball <cameron@moodle.com>
Date: Thu, 25 Jul 2019 07:22:07 +0000 (+0800)
Subject: Use Either for config errors instead of Maybe
X-Git-Url: http://cameron1729.xyz/?p=xyz.git;a=commitdiff_plain;h=b91e0acb3a2477f2b41e9d822dde3eb3bd7ceb2e

Use Either for config errors instead of Maybe
---

diff --git a/app/Main.hs b/app/Main.hs
index 6e38fcb..43b6039 100644
--- a/app/Main.hs
+++ b/app/Main.hs
@@ -45,16 +45,16 @@ getGlobalProjectConfig =  getGlobalProjectConfigPath >>= (\path -> doesFileExist
 getLocalProjectConfig :: IO (Maybe LocalConfig)
 getLocalProjectConfig = doesFileExist "xyz.json" >>= bool (return Nothing) (BL.readFile "xyz.json" >>= return . decode)
 
-resolveProjectConfig :: IO (Maybe ProjectConfig)
+resolveProjectConfig :: IO (Either Text ProjectConfig)
 resolveProjectConfig = do
   l <- getLocalProjectConfig
   g <- getGlobalProjectConfig
 
-  case (l, g) of
-    (Just l, Just g) -> return . Just $ getProjectConfig g l
-    (Just _, Nothing) -> fail "Busted global config"
-    (Nothing, Just _) -> fail "Busted local config"
-    _ -> fail "All configs are busted"
+  return $ case (l, g) of
+    (Just l, Just g) -> Right $ getProjectConfig g l
+    (Just _, Nothing) -> Left "Busted global config"
+    (Nothing, Just _) -> Left "Busted local config"
+    _ -> Left "All configs are busted"
 
 continueIfInvalidProject :: IO () -> IO ()
 continueIfInvalidProject next = doesFileExist "xyz.json" >>= bool next (putStrLn "Project already initialised")
@@ -85,7 +85,7 @@ init = do
   config <- resolveProjectConfig
 
   case config of
-    Just projectConfig -> do
+    Right projectConfig -> do
       createDirectory "entries"
 
       case (commitCommand (projectConfig :: ProjectConfig), gitRemote (projectConfig :: ProjectConfig)) of
@@ -94,8 +94,8 @@ init = do
         (_, _) -> return()
 
       putStrLn "\nInitialised empty project"
-    Nothing -> do
-      putStrLn "\nSomething went real wrong"
+    Left error -> do
+      putStrLn $ "\n" +++ error
 
 build :: ProjectConfig -> IO ()
 build config = allFilesIn "entries" >>= (writeOutProject config) >> putStrLn "Build successful"
@@ -149,10 +149,10 @@ usage =  putStr . ununlines $ [
                        ]
   ]
 
-gogogo :: (ProjectConfig -> IO ()) -> Maybe ProjectConfig -> IO ()
+gogogo :: (ProjectConfig -> IO ()) -> Either Text ProjectConfig -> IO ()
 gogogo next projectConfig = case projectConfig of
-  Just config -> next config
-  _ -> fail "This does not appear to be a vailid project directory" -- Never executes, the cases in resolveProjectConfig will fail first.
+  Right config -> next config
+  Left error -> putStrLn $ "This does not appear to be a vailid project directory: " +++ error -- Never executes, the cases in resolveProjectConfig will fail first.
 
 parse ["init"] =  initGlobalIfNeeded (continueIfInvalidProject init) >> exitSuccess
 parse ["build"] = resolveProjectConfig >>= (gogogo build) >> exitSuccess