Add FromField Integer

README.md

@@ -67,3 +67,5 @@ getScoreByAge conn = do
 - [ ] Implement JSON decoding
 - [ ] Implement `ByteString` decoding (`bytea`)
   - Can we make the fromField instance choose whether it wants binary or text?
+- [ ] Implement (anonymous) composite types
+  - It seems that in order to decode these, we'd need to use binary mode. In order to avoid writing everything twice it would be wise to move the whole `FromField` machinery to decoding from binary first

lib/Database/PostgreSQL/Opium/FromField.hs

@@ -41,22 +41,28 @@ class FromField a where
 
 -- | See https://www.postgresql.org/docs/current/datatype-character.html.
 instance FromField Text where
-  validOid _ = Oid.text \/ Oid.character \/ Oid.characterVarying
+  validOid Proxy = Oid.text \/ Oid.character \/ Oid.characterVarying
   parseField = takeText
 
 -- | See https://www.postgresql.org/docs/current/datatype-character.html.
 instance FromField String where
-  validOid _ = validOid @Text Proxy
+  validOid Proxy = validOid @Text Proxy
   parseField = Text.unpack <$> parseField
 
 -- | See https://www.postgresql.org/docs/current/datatype-character.html.
 -- This instance accepts all character types but fails to decode fields that are not exactly one character.
 instance FromField Char where
-  validOid _ = validOid @Text Proxy
+  validOid Proxy = validOid @Text Proxy
   parseField = anyChar
 
+-- | See https://www.postgresql.org/docs/current/datatype-numeric.html.
 instance FromField Int where
-  validOid _ = Oid.smallint \/ Oid.integer \/ Oid.bigint
+  validOid Proxy = Oid.smallint \/ Oid.integer \/ Oid.bigint
+  parseField = signed decimal
+
+-- | See https://www.postgresql.org/docs/current/datatype-numeric.html.
+instance FromField Integer where
+  validOid Proxy = Oid.smallint \/ Oid.integer \/ Oid.bigint
   parseField = signed decimal
 
 doubleParser :: Parser Double
@@ -70,11 +76,11 @@ doubleParser = choice
     infinity = 1 / 0
 
 instance FromField Float where
-  validOid _ = Oid.real
+  validOid Proxy = Oid.real
   parseField = fmap double2Float doubleParser
 
 instance FromField Double where
-  validOid _ = Oid.real \/ Oid.doublePrecision
+  validOid Proxy = Oid.real \/ Oid.doublePrecision
   parseField = doubleParser
 
 boolParser :: Parser Bool
@@ -85,5 +91,5 @@ boolParser = choice
 
 -- | See https://www.postgresql.org/docs/current/datatype-boolean.html.
 instance FromField Bool where
-  validOid _ = Oid.boolean
+  validOid Proxy = Oid.boolean
   parseField = boolParser

test/Database/PostgreSQL/Opium/FromFieldSpec.hs

@@ -18,6 +18,12 @@ newtype AnInt = AnInt
 
 instance FromRow AnInt where
 
+newtype AnInteger = AnInteger
+  { integer :: Integer
+  } deriving (Eq, Generic, Show)
+
+instance FromRow AnInteger where
+
 newtype AText = AText
   { text :: Text
   } deriving (Eq, Generic, Show)
@@ -72,7 +78,17 @@ spec = do
       shouldFetch conn "SELECT 42::INTEGER AS int" [AnInt 42]
 
     it "Decodes bigint" $ \conn -> do
-      shouldFetch conn "SELECT 42::BIGINT AS int" [AnInt 42]
+      shouldFetch conn "SELECT pow(2, 48)::BIGINT AS int" [AnInt $ (2 :: Int) ^ (48 :: Int)]
+
+  describe "FromField Integer" $ do
+    it "Decodes smallint" $ \conn -> do
+      shouldFetch conn "SELECT 42::SMALLINT AS integer" [AnInteger 42]
+
+    it "Decodes integer" $ \conn -> do
+      shouldFetch conn "SELECT pow(2, 20)::INTEGER AS integer" [AnInteger $ (2 :: Integer) ^ (20 :: Integer)]
+
+    it "Decodes bigint" $ \conn -> do
+      shouldFetch conn "SELECT pow(2, 48)::BIGINT AS integer" [AnInteger $ (2 :: Integer) ^ (48 :: Integer)]
 
   describe "FromField Text" $ do
     it "Decodes text" $ \conn -> do