tagged-json

tagged-json helps you derive aeson and openapi3 instances with a flat, explicitly-tagged JSON representation.

It is built around DerivingVia and one exported module: Deriving.TaggedJson.

What it provides

• Deriving via GTaggedJSON for:
  • ToJSON
  • FromJSON
  • ToSchema
  • ToKeyMap (helper class used by the generic JSON encoder)
• Flat object encoding (no extra wrapper nesting for constructors/newtypes)
• Explicit sum tags (tagKey) for unambiguous sum decoding
• Configurable field/constructor/datatype name modifiers
• Optional omission of Nothing fields during encoding
• Schema customization via SchemaDetails

Development

To run the tests, run:

cabal test

Formatting:

fourmolu -i .
cabal-fmt -i tagged-json.cabal

Linting:

hlint -j .

Usage example

See the runnable example in:

• example/Main.hs
• example/DerivingVia.hs

Run the example with:

cabal run tagged-json-example

Notes

• If a datatype has multiple constructors, tagKey must be set.
• If two types with the same name co-exist in the same OpenApi schema, their definitions will conflict.