Refactor getOptions

changelog.d/5-internal/refactor-get-options

@@ -0,0 +1 @@
+Refactor getOptions

libs/types-common/src/Util/Options.hs

@@ -31,7 +31,6 @@ import Data.Yaml hiding (Parser)
 import Imports
 import Options.Applicative
 import Options.Applicative.Types
-import System.Exit (die)
 import URI.ByteString
 import Util.Options.Common
 
@@ -111,7 +110,14 @@ loadSecret (FilePathSecrets p) = do
     then over _Left show . decodeEither' <$> BS.readFile path
     else pure (Left "File doesn't exist")
 
+-- | Get configuration options from the command line or configuration file.
+--
+-- This uses the provided optparse-applicative parser, if given. In all cases,
+-- it prepends a `config-file` option to the parser that accepts a file name.
+-- When that option is found, the config file is used to get the options,
+-- instead of the command line.
 getOptions ::
+  forall a.
   FromJSON a =>
   -- | Program description
   String ->
@@ -120,46 +126,40 @@ getOptions ::
   -- | Default config path, can be overridden with @--config-file@
   FilePath ->
   IO a
-getOptions desc pars defaultPath = do
-  path <- parseConfigPath defaultPath mkDesc
-  file <- doesFileExist path
-  case (file, pars) of
-    -- Config exists, we can just take options from there
+getOptions desc mp defaultPath = do
+  (path, mOpts) <-
+    execParser $
+      info
+        (optsOrConfigFile <**> helper)
+        (header desc <> fullDesc)
+  exists <- doesFileExist path
+  case (exists, mOpts) of
+    -- config file exists, take options from there
     (True, _) -> do
-      configFile <- decodeFileEither path
-      case configFile of
+      decodeFileEither path >>= \case
         Left e ->
           fail $
             show e
               <> " while attempting to decode "
-              <> show path
+              <> path
         Right o -> pure o
-    -- Config doesn't exist but at least we have a CLI options parser
-    (False, Just p) -> do
-      execParser (info (helper <*> p) mkDesc)
-    -- No config, no parser :(
-    (False, Nothing) -> do
-      die $ "Config file at " ++ path ++ " does not exist. \n"
-  where
-    mkDesc :: InfoMod b
-    mkDesc = header desc <> fullDesc
-
-parseConfigPath :: FilePath -> InfoMod String -> IO String
-parseConfigPath defaultPath desc = do
-  args <- getArgs
-  let result =
-        getParseResult $
-          execParserPure defaultPrefs (info (helper <*> pathParser) desc) args
-  pure $ fromMaybe defaultPath result
+    -- config doesn't exist, take options from command line
+    (False, Just opts) -> pure opts
+    -- no config, no parser, just fail
+    (False, Nothing) ->
+      fail $ "Config file at " <> path <> " does not exist."
   where
-    pathParser :: Parser String
-    pathParser =
-      strOption $
-        long "config-file"
-          <> short 'c'
-          <> help "Config file to load"
-          <> showDefault
-          <> value defaultPath
+    optsOrConfigFile :: Parser (FilePath, Maybe a)
+    optsOrConfigFile =
+      (,)
+        <$> strOption
+          ( long "config-file"
+              <> short 'c'
+              <> help "Config file to load"
+              <> showDefault
+              <> value defaultPath
+          )
+        <*> sequenceA mp
 
 parseAWSEndpoint :: ReadM AWSEndpoint
 parseAWSEndpoint = readerAsk >>= maybe (error "Could not parse AWS endpoint") pure . fromByteString . fromString