q.Ok and q.OkE

The comma-ok bubble — for map lookups, type assertions, channel receives, any API that returns (T, bool).

Signatures

func Ok[T any](v T, ok bool) T
func OkE[T any](v T, ok bool) OkResult[T]

var ErrNotOk = errors.New("q: not ok")

Bare q.Ok bubbles q.ErrNotOk — a package-level sentinel usable via errors.Is. q.OkE produces a richer error through the chain.

What q.Ok does

Two call-argument shapes are accepted. Single-call form — Go's f(g()) rule spreads the tuple:

v := q.Ok(lookup(key))            // lookup returns (T, bool)

Two-arg form — already destructured:

v, ok := table[key]
return q.Ok(v, ok), nil

Both rewrite to:

v, _qOk1 := <inner>
if !_qOk1 {
    return /* zeros */, q.ErrNotOk
}

Chain methods on q.OkE

There is no source error on the not-ok branch, so .ErrF takes a thunk, and .Wrap / .Wrapf build a fresh error (no %w).

Method	Bubbled error
.Err(replacement error)	replacement
.ErrF(fn func() error)	fn()
.Wrap(msg string)	errors.New(msg)
.Wrapf(format string, args ...any)	fmt.Errorf(format, args...)
.Catch(fn func() (T, error))	Recover with (v, nil) or bubble (_, err)

v := q.OkE(users[id]).Err(ErrNotFound)
v := q.OkE(users[id]).Wrapf("no user %d", id)
v := q.OkE(users[id]).Catch(func() (User, error) { return backfill(id) })

Statement forms

Same five positions as q.Try — define, assign, discard, return-position, hoist.

See also

• q.Recv — same pattern, specialised to channel receives.
• q.As — same pattern, specialised to type assertions.
• q.NotNil — the pointer-nil cousin, same vocabulary.