1 files changed, 64 insertions, 10 deletions

diff --git a/bazel/properties.go b/bazel/properties.go
index b370bbfb2..76be0581b 100644
--- a/bazel/properties.go
+++ b/bazel/properties.go
@@ -107,6 +107,14 @@ func (ll *LabelList) uniqueParentDirectories() []string {
 	return dirs
 }
 
+// Add inserts the label Label at the end of the LabelList.
+func (ll *LabelList) Add(label *Label) {
+	if label == nil {
+		return
+	}
+	ll.Includes = append(ll.Includes, *label)
+}
+
 // Append appends the fields of other labelList to the corresponding fields of ll.
 func (ll *LabelList) Append(other LabelList) {
 	if len(ll.Includes) > 0 || len(other.Includes) > 0 {
@@ -366,9 +374,23 @@ func (ba *BoolAttribute) SortedConfigurationAxes() []ConfigurationAxis {
 // labelListSelectValues supports config-specific label_list typed Bazel attribute values.
 type labelListSelectValues map[string]LabelList
 
-func (ll labelListSelectValues) appendSelects(other labelListSelectValues) {
+func (ll labelListSelectValues) addSelects(label labelSelectValues) {
+	for k, v := range label {
+		if label == nil {
+			continue
+		}
+		l := ll[k]
+		(&l).Add(v)
+		ll[k] = l
+	}
+}
+
+func (ll labelListSelectValues) appendSelects(other labelListSelectValues, forceSpecifyEmptyList bool) {
 	for k, v := range other {
 		l := ll[k]
+		if forceSpecifyEmptyList && l.IsNil() && !v.IsNil() {
+			l.Includes = []Label{}
+		}
 		(&l).Append(v)
 		ll[k] = l
 	}
@@ -424,17 +446,22 @@ func (cll configurableLabelLists) setValueForAxis(axis ConfigurationAxis, config
 	cll[axis][config] = list
 }
 
-func (cll configurableLabelLists) Append(other configurableLabelLists) {
+func (cll configurableLabelLists) Append(other configurableLabelLists, forceSpecifyEmptyList bool) {
 	for axis, otherSelects := range other {
 		selects := cll[axis]
 		if selects == nil {
 			selects = make(labelListSelectValues, len(otherSelects))
 		}
-		selects.appendSelects(otherSelects)
+		selects.appendSelects(otherSelects, forceSpecifyEmptyList)
 		cll[axis] = selects
 	}
 }
 
+func (lla *LabelListAttribute) Clone() *LabelListAttribute {
+	result := &LabelListAttribute{ForceSpecifyEmptyList: lla.ForceSpecifyEmptyList}
+	return result.Append(*lla)
+}
+
 // MakeLabelListAttribute initializes a LabelListAttribute with the non-arch specific value.
 func MakeLabelListAttribute(value LabelList) LabelListAttribute {
 	return LabelListAttribute{
@@ -488,16 +515,37 @@ func (lla *LabelListAttribute) SortedConfigurationAxes() []ConfigurationAxis {
 }
 
 // Append all values, including os and arch specific ones, from another
-// LabelListAttribute to this LabelListAttribute.
-func (lla *LabelListAttribute) Append(other LabelListAttribute) {
-	if lla.ForceSpecifyEmptyList && !other.Value.IsNil() {
+// LabelListAttribute to this LabelListAttribute. Returns this LabelListAttribute.
+func (lla *LabelListAttribute) Append(other LabelListAttribute) *LabelListAttribute {
+	forceSpecifyEmptyList := lla.ForceSpecifyEmptyList || other.ForceSpecifyEmptyList
+	if forceSpecifyEmptyList && lla.Value.IsNil() && !other.Value.IsNil() {
 		lla.Value.Includes = []Label{}
 	}
 	lla.Value.Append(other.Value)
 	if lla.ConfigurableValues == nil {
 		lla.ConfigurableValues = make(configurableLabelLists)
 	}
-	lla.ConfigurableValues.Append(other.ConfigurableValues)
+	lla.ConfigurableValues.Append(other.ConfigurableValues, forceSpecifyEmptyList)
+	return lla
+}
+
+// Add inserts the labels for each axis of LabelAttribute at the end of corresponding axis's
+// LabelList within the LabelListAttribute
+func (lla *LabelListAttribute) Add(label *LabelAttribute) {
+	if label == nil {
+		return
+	}
+
+	lla.Value.Add(label.Value)
+	if lla.ConfigurableValues == nil && label.ConfigurableValues != nil {
+		lla.ConfigurableValues = make(configurableLabelLists)
+	}
+	for axis, _ := range label.ConfigurableValues {
+		if _, exists := lla.ConfigurableValues[axis]; !exists {
+			lla.ConfigurableValues[axis] = make(labelListSelectValues)
+		}
+		lla.ConfigurableValues[axis].addSelects(label.ConfigurableValues[axis])
+	}
 }
 
 // HasConfigurableValues returns true if the attribute contains axis-specific label list values.
@@ -566,7 +614,7 @@ type OtherModuleContext interface {
 
 // LabelMapper is a function that takes a OtherModuleContext and returns a (potentially changed)
 // label and whether it was changed.
-type LabelMapper func(OtherModuleContext, string) (string, bool)
+type LabelMapper func(OtherModuleContext, Label) (string, bool)
 
 // LabelPartition contains descriptions of a partition for labels
 type LabelPartition struct {
@@ -588,7 +636,7 @@ type LabelPartitions map[string]LabelPartition
 // not.
 func (lf LabelPartition) filter(ctx OtherModuleContext, label Label) *Label {
 	if lf.LabelMapper != nil {
-		if newLabel, changed := lf.LabelMapper(ctx, label.Label); changed {
+		if newLabel, changed := lf.LabelMapper(ctx, label); changed {
 			return &Label{newLabel, label.OriginalModuleName}
 		}
 	}
@@ -757,12 +805,18 @@ func (sla StringListAttribute) HasConfigurableValues() bool {
 
 // Append appends all values, including os and arch specific ones, from another
 // StringListAttribute to this StringListAttribute
-func (sla *StringListAttribute) Append(other StringListAttribute) {
+func (sla *StringListAttribute) Append(other StringListAttribute) *StringListAttribute {
 	sla.Value = append(sla.Value, other.Value...)
 	if sla.ConfigurableValues == nil {
 		sla.ConfigurableValues = make(configurableStringLists)
 	}
 	sla.ConfigurableValues.Append(other.ConfigurableValues)
+	return sla
+}
+
+func (sla *StringListAttribute) Clone() *StringListAttribute {
+	result := &StringListAttribute{}
+	return result.Append(*sla)
 }
 
 // SetSelectValue set a value for a bazel select for the given axis, config and value.