More extensible way of doing validations

[v4n]

Any thoughts or plans or making custom validations more powerful such as allowing sql queries to be executed during the validation?

For example this is how to check if a record is unique in the database (using a ozzo-validation before c5ea90):

// UniqueRecord checks that a value is unique value in the database.
func UniqueRecord(statement string, bindvars ...interface{}) *uniqueRecord {
    return &uniqueRecord{
        message:   "Value is not unique.",
        statement: statement,
        bindvars:  bindvars,
    }
}

type uniqueRecord struct {
    message   string
    statement string
    bindvars  []interface{}
}

func (v *uniqueRecord) Validate(value interface{}, context interface{}) error {
    var exists bool
    statement := "SELECT EXISTS(" + v.statement + ")"
    err := database.SQL.Get(&exists, statement, v.bindvars...)
    if err != nil || exists {
        return errors.New(v.message)
    }
    return nil
}

To validate:

Add("Email", validation.Required, is.Email,     UniqueRecord(
  "SELECT 1 FROM email WHERE email=$1", invitation.Email)
)

This is no longer possible with the updates. It would be great being able to more than data-type validations and handle SQL queries validation and more complex struct validation such as check if two struct keys are not equal.

[v4n]

Actually never mind, I just realized that we don't depend on context anymore to do the SQL validation.