util/set: add some more Set operations (#10022)

Updates #cleanup

Signed-off-by: Chris Palmer <cpalmer@tailscale.com>

util/set/set.go

@@ -4,6 +4,10 @@
 // Package set contains set types.
 package set
 
+import (
+	"maps"
+)
+
 // Set is a set of T.
 type Set[T comparable] map[T]struct{}
 
@@ -14,16 +18,28 @@ func SetOf[T comparable](slice []T) Set[T] {
 	return s
 }
 
-// Add adds e to the set.
+// Clone returns a new set cloned from the elements in s.
+func Clone[T comparable](s Set[T]) Set[T] {
+	return maps.Clone(s)
+}
+
+// Add adds e to s.
 func (s Set[T]) Add(e T) { s[e] = struct{}{} }
 
-// AddSlice adds each element of es to the set.
+// AddSlice adds each element of es to s.
 func (s Set[T]) AddSlice(es []T) {
 	for _, e := range es {
 		s.Add(e)
 	}
 }
 
+// AddSet adds each element of es to s.
+func (s Set[T]) AddSet(es Set[T]) {
+	for e := range es {
+		s.Add(e)
+	}
+}
+
 // Slice returns the elements of the set as a slice. The elements will not be
 // in any particular order.
 func (s Set[T]) Slice() []T {
@@ -45,3 +61,8 @@ func (s Set[T]) Contains(e T) bool {
 
 // Len reports the number of items in s.
 func (s Set[T]) Len() int { return len(s) }
+
+// Equal reports whether s is equal to other.
+func (s Set[T]) Equal(other Set[T]) bool {
+	return maps.Equal(s, other)
+}

util/set/set_test.go

@@ -54,7 +54,7 @@ func TestSet(t *testing.T) {
 func TestSetOf(t *testing.T) {
 	s := SetOf[int]([]int{1, 2, 3, 4, 4, 1})
 	if s.Len() != 4 {
-		t.Errorf("wrong len %d; want 2", s.Len())
+		t.Errorf("wrong len %d; want 4", s.Len())
 	}
 	for _, n := range []int{1, 2, 3, 4} {
 		if !s.Contains(n) {
@@ -62,3 +62,53 @@ func TestSetOf(t *testing.T) {
 		}
 	}
 }
+
+func TestEqual(t *testing.T) {
+	type test struct {
+		name     string
+		a        Set[int]
+		b        Set[int]
+		expected bool
+	}
+	tests := []test{
+		{
+			"equal",
+			SetOf([]int{1, 2, 3, 4}),
+			SetOf([]int{1, 2, 3, 4}),
+			true,
+		},
+		{
+			"not equal",
+			SetOf([]int{1, 2, 3, 4}),
+			SetOf([]int{1, 2, 3, 5}),
+			false,
+		},
+		{
+			"different lengths",
+			SetOf([]int{1, 2, 3, 4, 5}),
+			SetOf([]int{1, 2, 3, 5}),
+			false,
+		},
+	}
+
+	for _, tt := range tests {
+		if tt.a.Equal(tt.b) != tt.expected {
+			t.Errorf("%s: failed", tt.name)
+		}
+	}
+}
+
+func TestClone(t *testing.T) {
+	s := SetOf[int]([]int{1, 2, 3, 4, 4, 1})
+	if s.Len() != 4 {
+		t.Errorf("wrong len %d; want 4", s.Len())
+	}
+	s2 := Clone(s)
+	if !s.Equal(s2) {
+		t.Error("clone not equal to original")
+	}
+	s.Add(100)
+	if s.Equal(s2) {
+		t.Error("clone is not distinct from original")
+	}
+}