func sorted()

in starlark/library.go [1000:1044]

• 40 lines of code
• 8 McCabe index (conditional complexity)

func sorted(thread *Thread, _ *Builtin, args Tuple, kwargs []Tuple) (Value, error) {
	// Oddly, Python's sorted permits all arguments to be positional, thus so do we.
	var iterable Iterable
	var key Callable
	var reverse bool
	if err := UnpackArgs("sorted", args, kwargs,
		"iterable", &iterable,
		"key?", &key,
		"reverse?", &reverse,
	); err != nil {
		return nil, err
	}

	iter := iterable.Iterate()
	defer iter.Done()
	var values []Value
	if n := Len(iterable); n > 0 {
		values = make(Tuple, 0, n) // preallocate if length is known
	}
	var x Value
	for iter.Next(&x) {
		values = append(values, x)
	}

	// Derive keys from values by applying key function.
	var keys []Value
	if key != nil {
		keys = make([]Value, len(values))
		for i, v := range values {
			k, err := Call(thread, key, Tuple{v}, nil)
			if err != nil {
				return nil, err // to preserve backtrace, don't modify error
			}
			keys[i] = k
		}
	}

	slice := &sortSlice{keys: keys, values: values}
	if reverse {
		sort.Stable(sort.Reverse(slice))
	} else {
		sort.Stable(slice)
	}
	return NewList(slice.values), slice.err
}