time: add Duration.Abs

Fixes #51414

Change-Id: Ia3b1674f2a902c8396fe029397536643a3bc1784
GitHub-Last-Rev: 67159648af
GitHub-Pull-Request: golang/go#51739
Reviewed-on: https://go-review.googlesource.com/c/go/+/393515
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Emmanuel Odeke <emmanuel@orijtech.com>

api/next/51414.txt

@@ -0,0 +1 @@
+pkg time, method (Duration) Abs() Duration #51414

src/time/time.go

@@ -815,6 +815,19 @@ func (d Duration) Round(m Duration) Duration {
 	return maxDuration // overflow
 }
 
+// Abs returns the absolute value of d.
+// As a special case, math.MinInt64 is converted to math.MaxInt64.
+func (d Duration) Abs() Duration {
+	switch {
+	case d >= 0:
+		return d
+	case d == minDuration:
+		return maxDuration
+	default:
+		return -d
+	}
+}
+
 // Add returns the time t+d.
 func (t Time) Add(d Duration) Time {
 	dsec := int64(d / 1e9)

src/time/time_test.go

@@ -1240,6 +1240,30 @@ func TestDurationRound(t *testing.T) {
 	}
 }
 
+var durationAbsTests = []struct {
+	d    Duration
+	want Duration
+}{
+	{0, 0},
+	{1, 1},
+	{-1, 1},
+	{1 * Minute, 1 * Minute},
+	{-1 * Minute, 1 * Minute},
+	{minDuration, maxDuration},
+	{minDuration + 1, maxDuration},
+	{minDuration + 2, maxDuration - 1},
+	{maxDuration, maxDuration},
+	{maxDuration - 1, maxDuration - 1},
+}
+
+func TestDurationAbs(t *testing.T) {
+	for _, tt := range durationAbsTests {
+		if got := tt.d.Abs(); got != tt.want {
+			t.Errorf("Duration(%s).Abs() = %s; want: %s", tt.d, got, tt.want)
+		}
+	}
+}
+
 var defaultLocTests = []struct {
 	name string
 	f    func(t1, t2 Time) bool