Merge pull request #874 from haskell/unit-proxy-deserialize

Accept all values in FromJSON () and FromJSON (Proxy tag)

Author: phadej

changelog.md

@@ -18,6 +18,8 @@ For the latest version of this document, please see [https://github.com/haskell/
 * `Double` and `Float` infinities are encoded as `"+inf"` and `"-inf"`.
   Change `To/FromJSONKey` instances to use `"+inf"` and `"-inf"` too.
 
+* `FromJSON ()` and `FromJSON (Proxy tag)` accept any JSON value.
+
 ### 1.5.6.0
 * Make `Show Value` instance print object keys in lexicographic order.
 

src/Data/Aeson/Types/FromJSON.hs

@@ -1527,10 +1527,7 @@ instance FromJSON Ordering where
                   " (expected \"LT\", \"EQ\", or \"GT\")"
 
 instance FromJSON () where
-    parseJSON = withArray "()" $ \v ->
-                  if V.null v
-                    then pure ()
-                    else prependContext "()" $ fail "expected an empty array"
+    parseJSON _ = pure ()
 
 instance FromJSON Char where
     parseJSON = withText "Char" parseChar
@@ -2283,10 +2280,10 @@ instance FromJSON1 S.Maybe where
 -------------------------------------------------------------------------------
 
 instance FromJSON1 Proxy where
-    liftParseJSON _ _ = fromNull "Proxy" Proxy
+    liftParseJSON _ _ _ = pure Proxy
 
 instance FromJSON (Proxy a) where
-    parseJSON = fromNull "Proxy" Proxy
+    parseJSON _ = pure Proxy
 
 fromNull :: String -> a -> Value -> Parser a
 fromNull _ a Null = pure a