transformer

Overview ¶

Package transformer provides struct-field transformation for REST requests using go-playground/mold. It is the conform/sanitize counterpart to the validator package and exposes mold's two faculties:

• modifiers (`mod:` tags) mutate fields in place — trim, lcase, default, snake, … — and are meant to run before validation so dirty input is cleaned first.
• scrubbers (`scrub:` tags) redact sensitive fields — emails, name, … — so a request struct can be logged safely.

The canonical request flow is decode → Transform (conform) → validate. Scrubbing mutates in place, so use ScrubbedCopy when the original value must be preserved (e.g. for logging a request that the handler still needs).

Basic usage:

type User struct {
    Name  string `json:"name"  mod:"trim"        validate:"required"  scrub:"name"`
    Email string `json:"email" mod:"trim,lcase" validate:"required,email" scrub:"emails"`
}

t := transformer.DefaultRestTransformer()
_ = t.Transform(ctx, &user) // conform: "  A@B.com " -> "a@b.com"
// ... validate, handle ...
safe, _ := transformer.ScrubbedCopy(ctx, t, &user) // redacted copy for logging

Custom transformations can be registered via RegisterModifier / RegisterScrubber, or by reaching the underlying mold transformers in the Modifiers / Scrubbers fields.