Generates OpenAPI 3.0 schema specifications directly from polytropos open records and variants.

Architectural Overview & Rationale

Schema Shape

• A record declares an anonymous object schema whose properties carry one entry per field (reified from the row symbols) and whose required list contains every field: a row-typed record is total, so all fields are required.
• A variant declares an anonymous oneOf schema with one entry per constructor, each a single-member tagged object {"ctor": fields} — the same wire shape Polytropos.Aeson uses, so REST APIs documented by these schemas round-trip seamlessly.

Eliminating Generic Schema Blow-up

Standard ToSchema deriving walks a GHC.Generics tree, which causes severe slowdowns on large schema models (50+ fields). polytropos-openapi3 synthesizes the schema by directly traversing the row type—one Declare step per field—with zero generic overhead.

When to Use This Module

• When documenting REST APIs, Swagger / OpenAPI endpoints that produce or consume polytropos records and variants.

Worked Example

{-# LANGUAGE DataKinds #-}
{-# LANGUAGE TypeApplications #-}
{-# OPTIONS_GHC -fplugin=Polytropos.Plugin #-}

import Data.OpenApi (toSchema, Schema)
import Data.Proxy (Proxy (..))
import Polytropos
import Polytropos.OpenApi

type User = Record '["id" ':= Int, "name" ':= String]

-- A conforming record value:
userVal :: User
userVal = REC { id = 1, name = "Alice" }

-- Generated OpenAPI schema with properties and required list in row order:
userSchema :: Schema
userSchema = toSchema (Proxy @User)