`Only [Field] -> `Only (N.NonEmpty Field)`

2 files changed, 11 insertions, 6 deletions

diff --git a/app/Main.hs b/app/Main.hs
index 23f2c9e..3cb3b79 100644
--- a/app/Main.hs
+++ b/app/Main.hs
@@ -1,17 +1,20 @@
 {-# LANGUAGE BlockArguments #-}
 {-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE ViewPatterns #-}
 {-# OPTIONS_GHC -fno-warn-name-shadowing #-}
 
 module Main where
 
 import Control.Exception (Exception, throw)
 import Control.Monad (void)
+import Control.Monad.Combinators.NonEmpty qualified as PN
 import Data.Aeson qualified as J
 import Data.Aeson.Key qualified as JK
 import Data.Aeson.KeyMap qualified as JM
 import Data.ByteString.Lazy.Char8 qualified as LB
 import Data.Char (isSpace)
 import Data.List (foldl', intercalate, isSuffixOf)
+import Data.List.NonEmpty qualified as N
 import Data.Maybe (catMaybes, fromMaybe, mapMaybe)
 import Data.Set qualified as S
 import Data.String (IsString (fromString))
@@ -65,7 +68,8 @@ instance Show Query where
         ]
     where
       showFieldSelector All = "*"
-      showFieldSelector (Only fs) = intercalate ", " (map showField fs)
+      showFieldSelector (Only (N.toList -> fs)) =
+        intercalate ", " (map showField fs)
       showField (Qualified c k) = c <> "." <> T.unpack k
       showField (Unqualified k) = T.unpack k
       showCollection c = c
@@ -104,7 +108,7 @@ instance Show Query where
 
 data FieldSelector
   = All
-  | Only [Field]
+  | Only (N.NonEmpty Field)
   deriving (Show)
 
 data Field
@@ -224,7 +228,7 @@ instance IsString Query where
               void $ lexeme $ P.string "*"
               pure All,
             do
-              Only <$> P.sepBy1 field comma
+              Only <$> PN.sepBy1 field comma
           ]
 
       field :: P.Parsec Void String Field
@@ -369,10 +373,10 @@ select (Only fs) vs =
               Qualified c k -> Just $ J.Object $ JM.singleton (JK.fromText (T.pack c <> "." <> k)) J.Null
               Unqualified k -> Just $ J.Object $ JM.singleton (JK.fromText k) J.Null
           )
-          fs
+          (N.toList fs)
 
-select' :: [Field] -> Record J.Value -> Record J.Value
-select' fs (Record c (J.Object kvs)) =
+select' :: N.NonEmpty Field -> Record J.Value -> Record J.Value
+select' (N.toList -> fs) (Record c (J.Object kvs)) =
   Record c . J.Object $
     JM.fromList . mapMaybe match . JM.toList $
       kvs
diff --git a/json2sql.cabal b/json2sql.cabal
index 3a39f88..5851d0e 100644
--- a/json2sql.cabal
+++ b/json2sql.cabal
@@ -33,6 +33,7 @@ executable json2sql
       gitlib-libgit2,
       megaparsec,
       mtl,
+      parser-combinators,
       tagged,
       text,
       unliftio,