Add a way to remove duplicates from Bazel label lists, to e.g. avoid duplicate deps.

Test: Added unit tests, and also resolves bp2build error.
Change-Id: I6e01d9e233ec21dbb244e5682cbeebbc3a1ac0c4

bazel/Android.bp

@@ -12,6 +12,7 @@ bootstrap_go_package {
     ],
     testSrcs: [
         "aquery_test.go",
+        "properties_test.go",
     ],
     pluginFor: [
         "soong_build",

bazel/properties.go

@@ -14,7 +14,10 @@
 
 package bazel
 
-import "fmt"
+import (
+	"fmt"
+	"sort"
+)
 
 type bazelModuleProperties struct {
 	// The label of the Bazel target replacing this Soong module.
@@ -66,6 +69,28 @@ func (ll *LabelList) Append(other LabelList) {
 	}
 }
 
+func UniqueBazelLabels(originalLabels []Label) []Label {
+	uniqueLabelsSet := make(map[Label]bool)
+	for _, l := range originalLabels {
+		uniqueLabelsSet[l] = true
+	}
+	var uniqueLabels []Label
+	for l, _ := range uniqueLabelsSet {
+		uniqueLabels = append(uniqueLabels, l)
+	}
+	sort.SliceStable(uniqueLabels, func(i, j int) bool {
+		return uniqueLabels[i].Label < uniqueLabels[j].Label
+	})
+	return uniqueLabels
+}
+
+func UniqueBazelLabelList(originalLabelList LabelList) LabelList {
+	var uniqueLabelList LabelList
+	uniqueLabelList.Includes = UniqueBazelLabels(originalLabelList.Includes)
+	uniqueLabelList.Excludes = UniqueBazelLabels(originalLabelList.Excludes)
+	return uniqueLabelList
+}
+
 // StringListAttribute corresponds to the string_list Bazel attribute type with
 // support for additional metadata, like configurations.
 type StringListAttribute struct {

bazel/properties_test.go

@@ -0,0 +1,89 @@
+// Copyright 2021 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package bazel
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestUniqueBazelLabels(t *testing.T) {
+	testCases := []struct {
+		originalLabels       []Label
+		expectedUniqueLabels []Label
+	}{
+		{
+			originalLabels: []Label{
+				{Label: "a"},
+				{Label: "b"},
+				{Label: "a"},
+				{Label: "c"},
+			},
+			expectedUniqueLabels: []Label{
+				{Label: "a"},
+				{Label: "b"},
+				{Label: "c"},
+			},
+		},
+	}
+	for _, tc := range testCases {
+		actualUniqueLabels := UniqueBazelLabels(tc.originalLabels)
+		if !reflect.DeepEqual(tc.expectedUniqueLabels, actualUniqueLabels) {
+			t.Fatalf("Expected %v, got %v", tc.expectedUniqueLabels, actualUniqueLabels)
+		}
+	}
+}
+
+func TestUniqueBazelLabelList(t *testing.T) {
+	testCases := []struct {
+		originalLabelList       LabelList
+		expectedUniqueLabelList LabelList
+	}{
+		{
+			originalLabelList: LabelList{
+				Includes: []Label{
+					{Label: "a"},
+					{Label: "b"},
+					{Label: "a"},
+					{Label: "c"},
+				},
+				Excludes: []Label{
+					{Label: "x"},
+					{Label: "x"},
+					{Label: "y"},
+					{Label: "z"},
+				},
+			},
+			expectedUniqueLabelList: LabelList{
+				Includes: []Label{
+					{Label: "a"},
+					{Label: "b"},
+					{Label: "c"},
+				},
+				Excludes: []Label{
+					{Label: "x"},
+					{Label: "y"},
+					{Label: "z"},
+				},
+			},
+		},
+	}
+	for _, tc := range testCases {
+		actualUniqueLabelList := UniqueBazelLabelList(tc.originalLabelList)
+		if !reflect.DeepEqual(tc.expectedUniqueLabelList, actualUniqueLabelList) {
+			t.Fatalf("Expected %v, got %v", tc.expectedUniqueLabelList, actualUniqueLabelList)
+		}
+	}
+}