Derivation of Aeson instances using GHC generics.

generic-aeson

The structure of the generated JSON is meant to be close to idiomatic JSON. This means:

• Enumerations (data types containing constructors without fields) are converted to JSON strings.

• Record fields become JSON keys.

• Data types with one unlabeled field convert to just that field.

• Data types with multiple unlabeled fields become arrays.

• Multiple constructors are represented by keys.

• Maybe values are either an absent key, or the value.

• Leading and trailing underscores are removed from constructor names and record fields

See tests/Main.hs in json-schema for more examples.

How does generic-aeson compare to the TH/Generics already present in aeson?

generic-aeson contains more special cases for creating more concise and idiomatic json. If you're working with the JSON representation directly generic-aeson should feel more natural.

Will the generated format ever change?

Changing the format would incur a breaking change to every API that uses generic-aeson so we must keep it intact.

If we find a bug where the fix changes the format we need to create a new package or version the generation code.

Schemas

json-schema has generic derivation of schemas that match the generic-aeson format.