OneofInstances.hs

{-# LANGUAGE TemplateHaskell #-}
{-# OPTIONS_GHC -Wno-orphans #-}

{- | Splice site for the oneof end-to-end regression. Loading
@test\/data\/oneof_regression.proto@ exercises the bridge\'s
@FKOneof@ path through 'Proto.TH.loadProto':

1. 'Proto.TH.mkOneofDataDecs' synthesises the @Envelope'Choice@
   sum type with one constructor per oneof arm.
2. 'Proto.TH.fieldSpecToProtoField' translates the @FSOneof@
   'FieldSpec' into a 'Proto.TH.Derive.Internal.FKOneof'
   'OneofVariant' list so the bridge can emit codecs.
3. 'messageCodecsViaBridge' produces @MessageEncode@ \/
   @MessageSize@ \/ @MessageDecode@ instances that pattern-
   match on the sum and dispatch on the variant tags.

The actual round-trip + variant-overwrite assertions live in
'Test.Proto.Derive.Oneof'.
-}
module Test.Proto.Derive.OneofInstances (
  -- * loadProto-generated types
  Envelope (..),
  Inner (..),
  Envelope'EnvelopeChoice (..),
  defaultEnvelope,
  defaultInner,
) where

import Data.Int (Int32)
import Data.Reflection (Given (..))
import Data.Text qualified as T
import Data.Vector qualified as V
import Proto.Internal.JSON.Extension (ExtensionRegistry, emptyExtensionRegistry)
import Proto.TH (loadProto)

-- TH-generated JSON instances carry a 'Given ExtensionRegistry' constraint
-- for proto2 extensions; this test target has none, so satisfy it with
-- the empty registry.
instance Given ExtensionRegistry where
  given = emptyExtensionRegistry


-- Keep the imports the loadProto splice transitively needs from
-- being optimised away.
_unused :: (V.Vector Int, T.Text, Int32)
_unused = (V.empty, T.empty, 0)


-- The splice creates: @Envelope@, @Inner@, @Envelope'EnvelopeChoice@
-- (the oneof sum), default values, and the wire-codec instance
-- triple via 'messageCodecsViaBridge'.
$(loadProto "test/data/oneof_regression.proto")