bake: skip empty attributes

bake/bake.go

@@ -1582,6 +1582,9 @@ type arrValue[B any] interface {
 func parseArrValue[T any, PT arrValue[T]](s []string) ([]*T, error) {
 	outputs := make([]*T, 0, len(s))
 	for _, text := range s {
+		if text == "" {
+			continue
+		}
 		output := new(T)
 		if err := PT(output).UnmarshalText([]byte(text)); err != nil {
 			return nil, err
@@ -1594,7 +1597,9 @@ func parseArrValue[T any, PT arrValue[T]](s []string) ([]*T, error) {
 func parseCacheArrValues(s []string) ([]*buildflags.CacheOptionsEntry, error) {
 	outs := make([]*buildflags.CacheOptionsEntry, 0, len(s))
 	for _, in := range s {
-		if !strings.Contains(in, "=") {
+		if in == "" {
+			continue
+		} else if !strings.Contains(in, "=") {
 			// This is ref only format. Each field in the CSV is its own entry.
 			fields, err := csvvalue.Fields(in, nil)
 			if err != nil {

bake/bake_test.go

@@ -2019,6 +2019,26 @@
 	})
 }
 
+// https://github.com/docker/buildx/pull/428
+// https://github.com/docker/buildx/issues/2822
+func TestEmptyAttribute(t *testing.T) {
+	fp := File{
+		Name: "docker-bake.hcl",
+		Data: []byte(`
+target "app" {
+  output = [""]
+}
+`),
+	}
+
+	ctx := context.TODO()
+
+	m, _, err := ReadTargets(ctx, []File{fp}, []string{"app"}, nil, nil)
+	require.Equal(t, 1, len(m))
+	require.Len(t, m["app"].Outputs, 0)
+	require.NoError(t, err)
+}
+
 func stringify[V fmt.Stringer](values []V) []string {
 	s := make([]string, len(values))
 	for i, v := range values {

util/buildflags/attests.go

@@ -21,9 +21,12 @@ func CanonicalizeAttest(attestType string, in string) string {
 }
 
 func ParseAttests(in []string) ([]*controllerapi.Attest, error) {
-	out := []*controllerapi.Attest{}
+	var out []*controllerapi.Attest
 	found := map[string]struct{}{}
 	for _, in := range in {
+		if in == "" {
+			continue
+		}
 		in := in
 		attest, err := ParseAttest(in)
 		if err != nil {

util/buildflags/cache.go

@@ -140,8 +140,11 @@ func (e *CacheOptionsEntry) validate(gv interface{}) error {
 }
 
 func ParseCacheEntry(in []string) ([]*controllerapi.CacheOptionsEntry, error) {
-	outs := make([]*controllerapi.CacheOptionsEntry, 0, len(in))
+	var outs []*controllerapi.CacheOptionsEntry
 	for _, in := range in {
+		if in == "" {
+			continue
+		}
 		var out CacheOptionsEntry
 		if err := out.UnmarshalText([]byte(in)); err != nil {
 			return nil, err

util/buildflags/context.go

@@ -13,6 +13,9 @@ func ParseContextNames(values []string) (map[string]string, error) {
 	}
 	result := make(map[string]string, len(values))
 	for _, value := range values {
+		if value == "" {
+			continue
+		}
 		kv := strings.SplitN(value, "=", 2)
 		if len(kv) != 2 {
 			return nil, errors.Errorf("invalid context value: %s, expected key=value", value)

util/buildflags/cty.go

@@ -179,5 +179,9 @@ func unmarshalTextFallback[V encoding.TextUnmarshaler](in cty.Value, v V, inErr
 
 	// Conversion was successful. Use UnmarshalText on the string and return any
 	// errors associated with that.
-	return v.UnmarshalText([]byte(conv.AsString()))
+	convstr := conv.AsString()
+	if convstr == "" {
+		return nil
+	}
+	return v.UnmarshalText([]byte(convstr))
 }

util/buildflags/entitlements.go

@@ -5,6 +5,9 @@ import "github.com/moby/buildkit/util/entitlements"
 func ParseEntitlements(in []string) ([]entitlements.Entitlement, error) {
 	out := make([]entitlements.Entitlement, 0, len(in))
 	for _, v := range in {
+		if v == "" {
+			continue
+		}
 		e, err := entitlements.Parse(v)
 		if err != nil {
 			return nil, err

util/buildflags/export.go

@@ -136,6 +136,9 @@ func ParseExports(inp []string) ([]*controllerapi.ExportEntry, error) {
 		return nil, nil
 	}
 	for _, s := range inp {
+		if s == "" {
+			continue
+		}
 		var out ExportEntry
 		if err := out.UnmarshalText([]byte(s)); err != nil {
 			return nil, err
@@ -153,6 +156,9 @@ func ParseAnnotations(inp []string) (map[exptypes.AnnotationKey]string, error) {
 
 	annotations := make(map[exptypes.AnnotationKey]string)
 	for _, inp := range inp {
+		if inp == "" {
+			continue
+		}
 		k, v, ok := strings.Cut(inp, "=")
 		if !ok {
 			return nil, errors.Errorf("invalid annotation %q, expected key=value", inp)

util/buildflags/secrets.go

@@ -85,6 +85,9 @@ func (s *Secret) UnmarshalText(text []byte) error {
 func ParseSecretSpecs(sl []string) ([]*controllerapi.Secret, error) {
 	fs := make([]*controllerapi.Secret, 0, len(sl))
 	for _, v := range sl {
+		if v == "" {
+			continue
+		}
 		s, err := parseSecret(v)
 		if err != nil {
 			return nil, err

util/buildflags/ssh.go

@@ -62,6 +62,9 @@ func ParseSSHSpecs(sl []string) ([]*controllerapi.SSH, error) {
 	}
 
 	for _, s := range sl {
+		if s == "" {
+			continue
+		}
 		var out SSH
 		if err := out.UnmarshalText([]byte(s)); err != nil {
 			return nil, err