Error handling in MVC mapper functions

[pantonov]

Consider the following example:

func (c *TodoController) BeforeActivation(b mvc.BeforeActivation) {
    b.Dependencies().Add(func(ctx iris.Context) (items []todo.Item) {
        ctx.ReadJSON(&items)
        return
    })
}

There is no way to process e.g. JSON conversion errors here. What about supporting second error return argument (or int HTTP error code), just like in normal mapped MVC methods, e.g.:

func (c *TodoController) BeforeActivation(b mvc.BeforeActivation) {
    b.Dependencies().Add(func(ctx iris.Context) (items []todo.Item, err error) {
        err = ctx.ReadJSON(&items)
        return
    })
}

when err != nil, status code 400 (+ err.Error() as body) should be sent as HTTP response and MVC method(s) not called.

[kataras]

@pantonov , I've just added support for second output of error type for the dynamic dependencies ^ for the upcoming v11.2 . Although you could already do that by:

	b.Dependencies().Add(func(ctx iris.Context) (v testCustomStruct) {
		err := ctx.ReadJSON(&v)
		if err != nil {
			ctx.StatusCode(iris.StatusBadRequest)
			ctx.WriteString(err.Error())
                        ctx.StopExecution() // this will stop the execution of a controller's method.
		}
		return
	})

[pantonov]

@kataras, that was a first thing I've tried, but ctx.StopExecution() by some reason did not work for me in this context. Controller function was called anyway despite ctx.StopExecution(). So I the only options were to pass error in context (or unexported field of testCustomStruct) and check it later in controller method.

[kataras]

Yes, this will work on the new version so you should be fine, if you don't mind you could try out the upcoming release by installing the v11.2.0 branch and give me more feedback if needed ( I added a _test for that case though)