OR Validation Operators in Go

Valgo provides Or() and OrElse() for expressing alternatives inside a validator chain. Both methods take no arguments and apply to the rules that surround them in the same chain.

Or

Or() groups adjacent rules into a logical OR expression. The group passes when any rule in it passes and fails only when every rule fails.

For example, accept a contact value that looks like either an email address or a phone number:

emailRe := regexp.MustCompile(`^.+@.+\..+$`)
phoneRe := regexp.MustCompile(`^\+?[0-9]{7,}$`)

val := v.Is(
  v.String(contact, "contact").
    MatchingTo(emailRe).
    Or().
    MatchingTo(phoneRe),
)

You can join more than two alternatives:

val := v.Is(
  v.Int(status, "status").
    EqualTo(1).
    Or().EqualTo(2).
    Or().EqualTo(3),
)

Precedence

An OR group is evaluated before the implicit AND that continues the chain:

v.String(value).
  MinLength(5).
  Or().EqualTo("test").
  Not().Blank()

This is evaluated as:

(MinLength(5) OR EqualTo("test")) AND Not().Blank()

Rules that fail before an OR group begins are not rescued by a later Or(). For example, A.B.Or().C is evaluated as A AND (B OR C).

Error messages

If every rule in an OR group fails, Valgo returns one message containing all the alternatives. The separator is localized for the validation session.

For example:

val := v.Is(
  v.Int(1, "status", "Status").
    EqualTo(2).
    Or().EqualTo(3),
)

Produces:

Status must be equal to "2" or Status must be equal to "3"

OrElse

OrElse() introduces an OR boundary with short-circuiting. If the rule or OR group to its left passes, the entire remainder of the validator chain is skipped. If the left side fails, validation continues on the right normally.

This is useful for optional values: accept an empty value immediately; otherwise, require every rule that follows it to pass.

val := v.Is(
  v.String(value, "value").
    Empty().
    OrElse().
    MinLength(5).
    EqualTo("test"),
)

This behaves as:

Empty() OR (MinLength(5) AND EqualTo("test"))

When Empty() passes, neither MinLength(5) nor EqualTo("test") is evaluated. When it fails, both rules on the right are evaluated using the normal Is() or Check() behavior.

OrElse() participates in an OR group like Or() and uses the same localized joined error format when all alternatives fail. It does not accept a custom message. To customize an error, pass a template to the relevant validation rule.