opt

Optionality is often implicitly represented by overloading the semantics of pointers or zeroness. This package exports the opt.T type and aliases for built-in types, to explicitly represent optional values.

Install

go get github.com/lukasngl/opt

Requires Go 1.22+.

Usage

type Query struct {
    OrderBy opt.T[OrderBy] `json:"orderBy,omitzero"`
    Limit   opt.Int        `json:"limit,omitzero"`
    Offset  opt.Int        `json:"offset,omitzero"`
}

value, ok := optional.Get()
if !ok {
    return fmt.Errorf("not present")
}

Features

• Concise: opt.T[V] and aliases like opt.Int keep declarations short.

• Idiomatic: Get() returns (value, ok), matching Go patterns like map lookup and type assertions.

• Compatible:

  • Pointers: Convert with FromPtr and ToPtr
  • Zero values: Convert with FromZeroable, honoring IsZero() methods
  • JSON: Implements json.Marshaler/Unmarshaler, with omitzero support (go1.24)
  • SQL: Implements driver.Valuer/sql.Scanner via sql.Null[V]
  • Iterators: All() returns iter.Seq[V] (Go 1.23+)

• Functional utilities: Map, FlatMap, Filter, Or, OrElseGet, IfPresent — for when you have a function ready to pass. Otherwise if v, ok := o.Get(); ok is usually cleaner.

Prior Art

There are loads of other optional type packages, but all of them had at least one of the following deal-breakers:

• Really long type names — the TypeScript folks just suffix a question mark, so why should we suffer?
• A slice-based approach — forces the value onto the heap and stores length and capacity, leading to unnecessary overhead.
• No IsZero() bool method for the omitzero tag.