buildx/util/buildflags/utils.go

package buildflags

import (
	"github.com/zclconf/go-cty/cty"
	"github.com/zclconf/go-cty/cty/gocty"
)

type comparable[E any] interface {
	Equal(other E) bool
}

func removeDupes[E comparable[E]](s []E) []E {
	// Move backwards through the slice.
	// For each element, any elements after the current element are unique.
	// If we find our current element conflicts with an existing element,
	// then we swap the offender with the end of the slice and chop it off.

	// Start at the second to last element.
	// The last element is always unique.
	for i := len(s) - 2; i >= 0; i-- {
		elem := s[i]
		// Check for duplicates after our current element.
		for j := i + 1; j < len(s); j++ {
			if elem.Equal(s[j]) {
				// Found a duplicate, exchange the
				// duplicate with the last element.
				s[j], s[len(s)-1] = s[len(s)-1], s[j]
				s = s[:len(s)-1]
				break
			}
		}
	}
	return s
}

func getAndDelete(m map[string]cty.Value, attr string, gv any) error {
	if v, ok := m[attr]; ok && v.IsKnown() {
		delete(m, attr)
		return gocty.FromCtyValue(v, gv)
	}
	return nil
}

func asMap(m map[string]cty.Value) map[string]string {
	out := make(map[string]string, len(m))
	for k, v := range m {
		if v.IsKnown() {
			out[k] = v.AsString()
		}
	}
	return out
}

func isEmptyOrUnknown(v cty.Value) bool {
	return !v.IsKnown() || (v.Type() == cty.String && v.AsString() == "")
}

// Seq is a temporary definition of iter.Seq until we are able to migrate
// to using go1.23 as our minimum version. This can be removed when go1.24
// is released and usages can be changed to use rangefunc.
type Seq[V any] func(yield func(V) bool)

func eachElement(in cty.Value) Seq[cty.Value] {
	return func(yield func(v cty.Value) bool) {
		for elem := in.ElementIterator(); elem.Next(); {
			_, value := elem.Element()
			if isEmptyOrUnknown(value) {
				continue
			}

			if !yield(value) {
				return
			}
		}
	}
}