Data.Aeson.Compat

Compatibility notices

• decode etc. work as in aeson >=0.9
• but it is generalised to work in any MonadThrow (that is extra)
• .:? works as in aeson <0.10
• .:! works as .:? in aeson ==0.10
• Orphan instances FromJSON Day and FromJSON LocalTime for aeson <0.10

Generic decoding functions

decode :: (FromJSON a, MonadThrow m) => ByteString -> m a

Like original decode but in arbitrary MonadThrow.

Parse a top-level JSON value, i.e. also strings, numbers etc.

decode' :: (FromJSON a, MonadThrow m) => ByteString -> m a

Like original decode' but in arbitrary MonadThrow.

decodeStrict :: (FromJSON a, MonadThrow m) => ByteString -> m a

Like original decodeStrict but in arbitrary MonadThrow.

decodeStrict' :: (FromJSON a, MonadThrow m) => ByteString -> m a

Like original decodeStrict' but in arbitrary MonadThrow.

newtype AesonException

Exception thrown by decode - family of functions in this module.

Constructors

AesonException String

Instances

Show AesonException

Methods

showsPrec :: Int -> AesonException -> ShowS

show :: AesonException -> String

showList :: [AesonException] -> ShowS

Exception AesonException

Methods

toException :: AesonException -> SomeException

fromException :: SomeException -> Maybe AesonException

displayException :: AesonException -> String

Either decoding functions

eitherDecode :: FromJSON a => ByteString -> Either String a

Like decode but returns an error message when decoding fails.

eitherDecode' :: FromJSON a => ByteString -> Either String a

Like decode' but returns an error message when decoding fails.

eitherDecodeStrict :: FromJSON a => ByteString -> Either String a

Like decodeStrict but returns an error message when decoding fails.

eitherDecodeStrict' :: FromJSON a => ByteString -> Either String a

Like decodeStrict' but returns an error message when decoding fails.

Operators

(.:?) :: FromJSON a => Object -> Text -> Parser (Maybe a)

Retrieve the value associated with the given key of an Object. The result is Nothing if the key is not present, or empty if the value cannot be converted to the desired type.

This accessor is most useful if the key and value can be absent from an object without affecting its validity. If the key and value are mandatory, use .: instead.

This operator is consistent in aeson >=0.7 && <0.11

(.:!) :: FromJSON a => Object -> Text -> Parser (Maybe a)

Like .:?, but the resulting parser will fail, if the key is present but is Null.

Re-exports

Original .:? operator is not re-exported

module Data.Aeson