A small package containing helpful addititions to aeson.
It provides eitherDecodeV and decodeV functions (analogous to eitherDecode and decode in aeson) that can be used to parse atomic JSON values at the top level. This is not strictly valid JSON, only objects and arrays are allowed at the top level in the specification, but aeson's encode allows this already. This gives us the nice property decodeV . encode = Just.
The package also contains the .=? operator that you can use to optionally construct object pairs:
object (
[ "a" .= foo
, "b" .= bar
] ++ catMaybes
[ "c" .=? mBaz
, "d" .=? mQux
])Finally it has a parseNumber function that converts a scientific into Either Integer Double in case you want to distinguish between integrals and fractionals.
aeson-utils is available on hackage
cabal install aeson-utils