implement Problem Details for HTTP APIs #1335

Former-commit-id: ff789b6d535080c88e05c81ab3fb7d9689801ec7

_examples/routing/http-errors/main.go

@@ -7,12 +7,15 @@ import (
 func main() {
 	app := iris.New()
 
+	// Catch a specific error code.
 	app.OnErrorCode(iris.StatusInternalServerError, func(ctx iris.Context) {
 		ctx.HTML("Message: <b>" + ctx.Values().GetString("message") + "</b>")
 	})
 
+	// Catch all error codes [app.OnAnyErrorCode...]
+
 	app.Get("/", func(ctx iris.Context) {
-		ctx.HTML(`Click <a href="/my500">here</a> to fire the 500 status code`)
+		ctx.HTML(`Click <a href="/my500">here</a> to pretend an HTTP error`)
 	})
 
 	app.Get("/my500", func(ctx iris.Context) {
@@ -24,5 +27,60 @@ func main() {
 		ctx.Writef("Hello %s", ctx.Params().Get("firstname"))
 	})
 
+	app.Get("/product-problem", problemExample)
+
+	app.Get("/product-error", func(ctx iris.Context) {
+		ctx.Writef("explain the error")
+	})
+
+	// http://localhost:8080
+	// http://localhost:8080/my500
+	// http://localhost:8080/u/gerasimos
+	// http://localhost:8080/product-problem
 	app.Run(iris.Addr(":8080"))
 }
+
+func newProductProblem(productName, detail string) iris.Problem {
+	return iris.NewProblem().
+		// The type URI, if relative it automatically convert to absolute.
+		Type("/product-error").
+		// The title, if empty then it gets it from the status code.
+		Title("Product validation problem").
+		// Any optional details.
+		Detail(detail).
+		// The status error code, required.
+		Status(iris.StatusBadRequest).
+		// Any custom key-value pair.
+		Key("productName", productName)
+	// Optional cause of the problem, chain of Problems.
+	// Cause(iris.NewProblem().Type("/error").Title("cause of the problem").Status(400))
+}
+
+func problemExample(ctx iris.Context) {
+	/*
+		p := iris.NewProblem().
+			Type("/validation-error").
+			Title("Your request parameters didn't validate").
+			Detail("Optional details about the error.").
+			Status(iris.StatusBadRequest).
+		 	Key("customField1", customValue1)
+		 	Key("customField2", customValue2)
+		ctx.Problem(p)
+
+		// OR
+		ctx.Problem(iris.Problem{
+			"type":   "/validation-error",
+			"title":  "Your request parameters didn't validate",
+			"detail": "Optional details about the error.",
+			"status": iris.StatusBadRequest,
+		 	"customField1": customValue1,
+		 	"customField2": customValue2,
+		})
+
+		// OR
+	*/
+
+	// Response like JSON but with indent of "  " and
+	// content type of "application/problem+json"
+	ctx.Problem(newProductProblem("product name", "problem error details"))
+}