From b7e1a48376e80feb5501fae0f6ec97001e111b74 Mon Sep 17 00:00:00 2001
From: Jihoon Kang <jihoonkang@google.com>
Date: Wed, 26 Jun 2024 22:11:02 +0000
Subject: [PATCH] Add util method HasIntersection(...)

Introduces a util method `HasIntersection(...)`, which returns true if
the two input lists have non-empty intersection.

Test: m nothing --no-skip-soong-tests
Bug: 338660802
Change-Id: I861a60e1973c92a773c127dfc595ad7514d7972f
---
 android/util.go      |  6 ++++++
 android/util_test.go | 49 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 55 insertions(+)

diff --git a/android/util.go b/android/util.go
index e21e66b88..3c0af2f38 100644
--- a/android/util.go
+++ b/android/util.go
@@ -201,6 +201,12 @@ func ListSetDifference[T comparable](l1, l2 []T) (bool, []T, []T) {
 	return listsDiffer, diff1, diff2
 }
 
+// Returns true if the two lists have common elements.
+func HasIntersection[T comparable](l1, l2 []T) bool {
+	_, a, b := ListSetDifference(l1, l2)
+	return len(a)+len(b) < len(setFromList(l1))+len(setFromList(l2))
+}
+
 // Returns true if the given string s is prefixed with any string in the given prefix list.
 func HasAnyPrefix(s string, prefixList []string) bool {
 	for _, prefix := range prefixList {
diff --git a/android/util_test.go b/android/util_test.go
index 8e73d835c..6537d69b9 100644
--- a/android/util_test.go
+++ b/android/util_test.go
@@ -818,3 +818,52 @@ func TestReverseSlice(t *testing.T) {
 		})
 	}
 }
+
+var hasIntersectionTestCases = []struct {
+	name     string
+	l1       []string
+	l2       []string
+	expected bool
+}{
+	{
+		name:     "empty",
+		l1:       []string{"a", "b", "c"},
+		l2:       []string{},
+		expected: false,
+	},
+	{
+		name:     "both empty",
+		l1:       []string{},
+		l2:       []string{},
+		expected: false,
+	},
+	{
+		name:     "identical",
+		l1:       []string{"a", "b", "c"},
+		l2:       []string{"a", "b", "c"},
+		expected: true,
+	},
+	{
+		name:     "duplicates",
+		l1:       []string{"a", "a", "a"},
+		l2:       []string{"a", "b", "c"},
+		expected: true,
+	},
+	{
+		name:     "duplicates with no intersection",
+		l1:       []string{"d", "d", "d", "d"},
+		l2:       []string{"a", "b", "c"},
+		expected: false,
+	},
+}
+
+func TestHasIntersection(t *testing.T) {
+	for _, testCase := range hasIntersectionTestCases {
+		t.Run(testCase.name, func(t *testing.T) {
+			hasIntersection := HasIntersection(testCase.l1, testCase.l2)
+			if !reflect.DeepEqual(hasIntersection, testCase.expected) {
+				t.Errorf("expected %#v, got %#v", testCase.expected, hasIntersection)
+			}
+		})
+	}
+}