refactor(core): re-add handlers (#21575)

core/appmodule/v2/handlers.go

@@ -2,6 +2,7 @@ package appmodulev2
 
 import (
 	"context"
+	"fmt"
 
 	transaction "cosmossdk.io/core/transaction"
 )
@@ -16,47 +17,152 @@ type (
 	PostMsgHandler = func(ctx context.Context, msg, msgResp transaction.Msg) error
 )
 
-// msg handler
-
+// PreMsgRouter is a router that allows you to register PreMsgHandlers for specific message types.
 type PreMsgRouter interface {
 	// RegisterPreHandler will register a specific message handler hooking into the message with
 	// the provided name.
-	RegisterPreHandler(msgName string, handler PreMsgHandler)
+	RegisterPreMsgHandler(msgName string, handler PreMsgHandler)
 	// RegisterGlobalPreHandler will register a global message handler hooking into any message
 	// being executed.
-	RegisterGlobalPreHandler(handler PreMsgHandler)
+	RegisterGlobalPreMsgHandler(handler PreMsgHandler)
 }
 
+// HasPreMsgHandlers is an interface that modules must implement if they want to register PreMsgHandlers.
 type HasPreMsgHandlers interface {
 	RegisterPreMsgHandlers(router PreMsgRouter)
 }
 
-type MsgRouter interface {
-	Register(msgName string, handler Handler)
-}
+// RegisterMsgPreHandler is a helper function that modules can use to not lose type safety when registering PreMsgHandler to the
+// PreMsgRouter. Example usage:
+// ```go
+//
+//	func (h Handlers) BeforeSend(ctx context.Context, req *types.MsgSend) error {
+//	      ... before send logic ...
+//	}
+//
+//	func (m Module) RegisterPreMsgHandlers(router appmodule.PreMsgRouter) {
+//		handlers := keeper.NewHandlers(m.keeper)
+//	    appmodule.RegisterMsgPreHandler(router, gogoproto.MessageName(types.MsgSend{}), handlers.BeforeSend)
+//	}
+//
+// ```
+func RegisterMsgPreHandler[Req transaction.Msg](
+	router PreMsgRouter,
+	msgName string,
+	handler func(ctx context.Context, msg Req) error,
+) {
+	untypedHandler := func(ctx context.Context, m transaction.Msg) error {
+		typed, ok := m.(Req)
+		if !ok {
+			return fmt.Errorf("unexpected type %T, wanted: %T", m, *new(Req))
+		}
+		return handler(ctx, typed)
+	}
 
-type HasMsgHandlers interface {
-	RegisterMsgHandlers(router MsgRouter)
+	router.RegisterPreMsgHandler(msgName, untypedHandler)
 }
 
+// PostMsgRouter is a router that allows you to register PostMsgHandlers for specific message types.
 type PostMsgRouter interface {
 	// RegisterPostHandler will register a specific message handler hooking after the execution of message with
 	// the provided name.
-	RegisterPostHandler(msgName string, handler PostMsgHandler)
+	RegisterPostMsgHandler(msgName string, handler PostMsgHandler)
 	// RegisterGlobalPostHandler will register a global message handler hooking after the execution of any message.
-	RegisterGlobalPostHandler(handler PostMsgHandler)
+	RegisterGlobalPostMsgHandler(handler PostMsgHandler)
 }
 
+// HasPostMsgHandlers is an interface that modules must implement if they want to register PostMsgHandlers.
 type HasPostMsgHandlers interface {
 	RegisterPostMsgHandlers(router PostMsgRouter)
 }
 
-// query handler
+// RegisterPostHandler is a helper function that modules can use to not lose type safety when registering handlers to the
+// PostMsgRouter. Example usage:
+// ```go
+//
+//	func (h Handlers) AfterSend(ctx context.Context, req *types.MsgSend, resp *types.MsgSendResponse) error {
+//	      ... query logic ...
+//	}
+//
+//	func (m Module) RegisterPostMsgHandlers(router appmodule.PostMsgRouter) {
+//		handlers := keeper.NewHandlers(m.keeper)
+//	    appmodule.RegisterPostMsgHandler(router, gogoproto.MessageName(types.MsgSend{}), handlers.AfterSend)
+//	}
+//
+// ```
+func RegisterPostMsgHandler[Req, Resp transaction.Msg](
+	router PostMsgRouter,
+	msgName string,
+	handler func(ctx context.Context, msg Req, msgResp Resp) error,
+) {
+	untypedHandler := func(ctx context.Context, m, mResp transaction.Msg) error {
+		typed, ok := m.(Req)
+		if !ok {
+			return fmt.Errorf("unexpected type %T, wanted: %T", m, *new(Req))
+		}
+		typedResp, ok := mResp.(Resp)
+		if !ok {
+			return fmt.Errorf("unexpected type %T, wanted: %T", m, *new(Resp))
+		}
+		return handler(ctx, typed, typedResp)
+	}
 
-type QueryRouter interface {
-	Register(queryName string, handler Handler)
+	router.RegisterPostMsgHandler(msgName, untypedHandler)
 }
 
+// MsgRouter is a router that allows you to register Handlers for specific message types.
+type MsgRouter = interface {
+	RegisterHandler(msgName string, handler Handler) error
+}
+
+// HasMsgHandlers is an interface that modules must implement if they want to register Handlers.
+type HasMsgHandlers interface {
+	RegisterMsgHandlers(router MsgRouter)
+}
+
+// QueryRouter is a router that allows you to register QueryHandlers for specific query types.
+type QueryRouter = MsgRouter
+
+// HasQueryHandlers is an interface that modules must implement if they want to register QueryHandlers.
 type HasQueryHandlers interface {
 	RegisterQueryHandlers(router QueryRouter)
 }
+
+// RegisterMsgHandler is a helper function that modules can use to not lose type safety when registering handlers to the MsgRouter and Query Router.
+// Example usage:
+// ```go
+//
+//	func (h Handlers) Mint(ctx context.Context, req *types.MsgMint) (*types.MsgMintResponse, error) {
+//	      ... msg logic ...
+//	}
+//
+//	func (h Handlers) QueryBalance(ctx context.Context, req *types.QueryBalanceRequest) (*types.QueryBalanceResponse, error) {
+//	      ... query logic ...
+//	}
+//
+//	func (m Module) RegisterMsgHandlers(router appmodule.MsgRouter) {
+//		handlers := keeper.NewHandlers(m.keeper)
+//	    err := appmodule.RegisterHandler(router, gogoproto.MessageName(types.MsgMint{}), handlers.MsgMint)
+//	}
+//
+//	func (m Module) RegisterQueryHandlers(router appmodule.QueryRouter) {
+//		handlers := keeper.NewHandlers(m.keeper)
+//	    err := appmodule.RegisterHandler(router, gogoproto.MessageName(types.QueryBalanceRequest{}), handlers.QueryBalance)
+//	}
+//
+// ```
+func RegisterHandler[Req, Resp transaction.Msg](
+	router MsgRouter,
+	msgName string,
+	handler func(ctx context.Context, msg Req) (msgResp Resp, err error),
+) error {
+	untypedHandler := func(ctx context.Context, m transaction.Msg) (transaction.Msg, error) {
+		typed, ok := m.(Req)
+		if !ok {
+			return nil, fmt.Errorf("unexpected type %T, wanted: %T", m, *new(Req))
+		}
+		return handler(ctx, typed)
+	}
+
+	return router.RegisterHandler(msgName, untypedHandler)
+}