validation

Overview ¶

Package validation provides a dependency-free, Laravel-FormRequest-grade request validator for structs and maps.

Two entry points cover most needs:

• Validate(v) walks a struct's `validate:"..."` tags and applies rules.
• Map(data, rules) validates a map[string]any (e.g. decoded JSON) against a programmatic Rules table — no struct required.

Field names in errors use the `json` tag when present, otherwise the struct field name.

Struct example:

type RegisterRequest struct {
    Name                 string `json:"name" validate:"required,max=255"`
    Email                string `json:"email" validate:"required,email"`
    Age                  int    `json:"age" validate:"gte=18,lte=120"`
    Password             string `json:"password" validate:"required,min=8"`
    PasswordConfirmation string `json:"password_confirmation"`
    Role                 string `json:"role" validate:"in=admin|user|guest"`
}

var req RegisterRequest
if err := validation.Validate(&req); err != nil {
    var ve validation.ValidationErrors
    if errors.As(err, &ve) {
        // c.JSON(422, validation.Response(ve))
    }
}

The "confirmed" rule pairs a field with "<Field>Confirmation" (or its json "<field>_confirmation"), matching Laravel's password/password_confirmation convention.

Map example (no struct):

data := map[string]any{"email": "bad", "age": 5}
err := validation.Map(data, validation.Rules{
    "email": {"required", "email"},
    "age":   {"required", "integer", "gte=18"},
})

Web integration. validation is a leaf package and never imports web, so to avoid an import cycle it exposes only the response *shape*. Callers wire it:

func (h *Handler) Store(c *web.Context) (any, error) {
    var req RegisterRequest
    if err := c.Bind(&req); err != nil {
        return nil, err
    }
    if err := validation.Validate(&req); err != nil {
        var ve validation.ValidationErrors
        if errors.As(err, &ve) {
            c.JSON(422, validation.Response(ve))
            return nil, nil
        }
        return nil, err
    }
    return req, nil
}