add x/errors.Validation

HISTORY.md

@@ -23,6 +23,7 @@ Developers are not forced to upgrade if they don't really need it. Upgrade whene
 
 Changes apply to `main` branch.
 
+- Add `x/errors.Validation` package-level function to add one or more validations for the request payload before a service call of the below methods.
 - Add `x/errors.Handler`, `CreateHandler`, `NoContentHandler`, `NoContenetOrNotModifiedHandler` and `ListHandler` ready-to-use handlers for service method calls to Iris Handler.
 - Add `x/errors.List` package-level function to support `ListObjects(ctx context.Context, opts pagination.ListOptions, f Filter) ([]Object, int64, error)` type of service calls.
 - Simplify how validation errors on `/x/errors` package works. A new `x/errors/validation` sub-package added to make your life easier (using the powerful Generics feature).

_examples/routing/http-wire-errors/service/main.go

@@ -12,14 +12,35 @@ import (
 
 func main() {
 	app := iris.New()
+
+	/*
+		service := new(myService)
+
+		app.Post("/", createHandler(service))              // OR: errors.CreateHandler(service.Create)
+		app.Get("/", listAllHandler(service))              // OR errors.Handler(service.ListAll, errors.Value(ListRequest{}))
+		app.Post("/page", listHandler(service))            // OR: errors.ListHandler(service.ListPaginated)
+		app.Delete("/{id:string}", deleteHandler(service)) // OR: errors.NoContentOrNotModifiedHandler(service.DeleteWithFeedback, errors.PathParam[string]("id"))
+	*/
+
+	app.PartyConfigure("/", Party())
+	app.Listen(":8080")
+}
+
+func Party() *party {
+	return &party{}
+}
+
+type party struct{}
+
+func (p *party) Configure(r iris.Party) {
 	service := new(myService)
 
-	app.Post("/", createHandler(service))              // OR: errors.CreateHandler(service.Create)
-	app.Get("/", listAllHandler(service))              // OR errors.Handler(service.ListAll, errors.Value(ListRequest{}))
-	app.Post("/page", listHandler(service))            // OR: errors.ListHandler(service.ListPaginated)
-	app.Delete("/{id:string}", deleteHandler(service)) // OR: errors.NoContentOrNotModifiedHandler(service.DeleteWithFeedback, errors.PathParam[string]("id"))
+	r.Post("/", createHandler(service)) // OR: errors.CreateHandler(service.Create)
 
-	app.Listen(":8080")
+	// add a custom validation function for the CreateRequest struct.
+	r.Get("/", listAllHandler(service))              // OR errors.Handler(service.ListAll, errors.Value(ListRequest{}))
+	r.Post("/page", listHandler(service))            // OR: errors.ListHandler(service.ListPaginated)
+	r.Delete("/{id:string}", deleteHandler(service)) // OR: errors.NoContentOrNotModifiedHandler(service.DeleteWithFeedback, errors.PathParam[string]("id"))
 }
 
 func createHandler(service *myService) iris.Handler {
@@ -97,6 +118,18 @@ type (
 // It validates the request body and returns an error if the request body is invalid.
 // You can also alter the "r" CreateRequest before calling the service method,
 // e.g. give a default value to a field if it's empty or set an ID based on a path parameter.
+// OR
+// Custom function per route:
+//
+//	r.Post("/", errors.Validation(validateCreateRequest), createHandler(service))
+//	[more code here...]
+//	func validateCreateRequest(ctx iris.Context, r *CreateRequest) error {
+//		return validation.Join(
+//			validation.String("fullname", r.Fullname).NotEmpty().Fullname().Length(3, 50),
+//			validation.Number("age", r.Age).InRange(18, 130),
+//			validation.Slice("hobbies", r.Hobbies).Length(1, 10),
+//		)
+//	}
 func (r *CreateRequest) ValidateContext(ctx iris.Context) error {
 	// To pass custom validation functions:
 	// return validation.Join(

x/errors/handlers.go

@@ -117,22 +117,93 @@ type ResponseOnlyErrorFunc[T any] interface {
 	func(stdContext.Context, T) error
 }
 
+// ContextValidatorFunc is a function which takes a context and a generic type T and returns an error.
+// It is used to validate the context before calling a service function.
+//
+// See Validation package-level function.
+type ContextValidatorFunc[T any] func(*context.Context, T) error
+
+const contextValidatorFuncKey = "iris.errors.ContextValidatorFunc"
+
+// Validation adds a context validator function to the context.
+// It returns a middleware which can be used to validate the context before calling a service function.
+// It panics if the given validators are empty or nil.
+//
+// Example:
+//
+// r.Post("/", Validation(validateCreateRequest), createHandler(service))
+//
+//	func validateCreateRequest(ctx iris.Context, r *CreateRequest) error {
+//		return validation.Join(
+//			validation.String("fullname", r.Fullname).NotEmpty().Fullname().Length(3, 50),
+//			validation.Number("age", r.Age).InRange(18, 130),
+//			validation.Slice("hobbies", r.Hobbies).Length(1, 10),
+//		)
+//	}
+func Validation[T any](validators ...ContextValidatorFunc[T]) context.Handler {
+	validator := joinContextValidators[T](validators)
+
+	return func(ctx *context.Context) {
+		ctx.Values().Set(contextValidatorFuncKey, validator)
+		ctx.Next()
+	}
+}
+
+func joinContextValidators[T any](validators []ContextValidatorFunc[T]) ContextValidatorFunc[T] {
+	if len(validators) == 0 || validators[0] == nil {
+		panic("at least one validator is required")
+	}
+
+	if len(validators) == 1 {
+		return validators[0]
+	}
+
+	return func(ctx *context.Context, req T) error {
+		for _, validator := range validators {
+			if validator == nil {
+				continue
+			}
+
+			if err := validator(ctx, req); err != nil {
+				return err
+			}
+		}
+
+		return nil
+	}
+}
+
 // ContextValidator is an interface which can be implemented by a request payload struct
 // in order to validate the context before calling a service function.
 type ContextValidator interface {
 	ValidateContext(*context.Context) error
 }
 
-func validateContext(ctx *context.Context, req any) bool {
+func validateContext[T any](ctx *context.Context, req T) bool {
+	var err error
+
+	// Always run the request's validator first,
+	// so dynamic validators can be customized per path and method.
 	if contextValidator, ok := any(&req).(ContextValidator); ok {
-		err := contextValidator.ValidateContext(ctx)
-		if err != nil {
-			if HandleError(ctx, err) {
-				return false
+		err = contextValidator.ValidateContext(ctx)
+	}
+
+	if err == nil {
+		if v := ctx.Values().Get(contextValidatorFuncKey); v != nil {
+			if contextValidatorFunc, ok := v.(ContextValidatorFunc[T]); ok {
+				err = contextValidatorFunc(ctx, req)
+			} else if contextValidatorFunc, ok := v.(ContextValidatorFunc[*T]); ok { // or a pointer of T.
+				err = contextValidatorFunc(ctx, &req)
 			}
 		}
 	}
 
+	if err != nil {
+		if HandleError(ctx, err) {
+			return false
+		}
+	}
+
 	return true
 }