Zog v0.15 with support for validating schemas directly (without parsing) to be released this week

[Oudwins]

Hey everyone!

I wanted to have gotten this feature out before the end of the holidays but I didn't end up having enough time. But this week I powered through and have it built! Zog 0.15 will come with a new Validate schema method which will recursively validate a value (struct, slice, etc). Without the need for parsing!

You'll now be able to do:

	type TestStruct struct {
		Somefield string
	}
	schema := Struct(Schema{
		"somefield": String().Required(),
	})
	test := TestStruct{
		Somefield: "someValue",
	}
	errs := schema.Validate(&test)

Validate Will support all existing tests, pretransforms, posttransforms, etc. And should be much faster than Parse

Limitations

There two main limitations with the Validate method:
1 No support for type coercion. For obvious reasons. So if you need to coerce a data string to a time.Time you will still need to use Parse or coerce the data manually before validation.

2 When Executing a Validation the required test will cause an error if the value is the zero value for its type
The main reason for this is that there is no way for Zog to know if that value was defined or not. And I did not want to add yet another test like NotZero() to check that the value is not a zero value as that might lead to schemas like z.String().Required().NotZero() if you are using both parse and validate.

If you are using validate and want to have a required value that accepts the zero value for its type you can do it like this:

type User struct {
   Age *int
}
userSchema := z.Struct(z.Schema{
"age": z.Ptr(z.Int()).NotNil()
})
// now if you unmarshal json into a User the age property will be nill if it is not found in the json and the schema will generate an error message