Proposal: Produce efficient errors instead raw panic message

[ilgooz]

I always like to check my form fields to see if their values are convertible to needed types and if not then inform the user about invalid fields. form produces *errors.errorString and this is not useful when generating error responses for this purpose.

What about defining a new error type such as below to give more control over them

e.g.

type Error []Field

func (e Error) Error() string {
  return "todo"
}

type Field struct {
  Name string // tag name e.g. time from form:"time"
  Message string // original error message 
  Type reflect.Type // point out the expected type so we can generate even more graceful error messages by checking this e.g. "time must be a UTC date"
  SliceIndex int // point out the index if an invalid Type placed in a slice except []byte
}

A dummy usage:

type Post struct {
  Time time.Time `form:"time"`
}

var p Post
err := form.DecodeValues(&p, url.Values{"time", []string{"AnInvalidDate"}})
if (err.(form.Error))[0].Type == form.TimeType {
 // so I can response a nice error message to user like:
 // HTTP 400
 // {"message": "Invalid Form Data", fields: {"time": "must be UTC formatted"}}
}

I'd like to implement this if you'll consider accepting the PR

[ajg]

@ilgooz Sorry for the late response. I would not mind extending the error returned by form in the manner you propose, if you'd like to implement it. Feel free to open a PR and assign it to me.

[ajg]

(I'm closing this issue due to inactivity for more than a year. Please re-open if it's still relevant. Thank you.)