From 4cb5949d1495fe47bfda85f3590a11b3a663717d Mon Sep 17 00:00:00 2001
From: Henrik Holst <6200749+hholst80@users.noreply.github.com>
Date: Fri, 3 May 2024 10:51:42 -0400
Subject: [PATCH] time: fix the string representation of a negative Duration
 (#21407)

---
 vlib/time/duration.v      | 17 +++++++++++------
 vlib/time/duration_test.v |  8 ++++++++
 2 files changed, 19 insertions(+), 6 deletions(-)

diff --git a/vlib/time/duration.v b/vlib/time/duration.v
index bd7f947061..cfa58d06e7 100644
--- a/vlib/time/duration.v
+++ b/vlib/time/duration.v
@@ -63,7 +63,12 @@ pub fn (d Duration) str() string {
 	if d == time.infinite {
 		return 'inf'
 	}
+	mut sign := ''
 	mut t := i64(d)
+	if t < 0 {
+		sign = '-'
+		t = -t
+	}
 	hr := t / time.hour
 	t -= hr * time.hour
 	min := t / time.minute
@@ -77,12 +82,12 @@ pub fn (d Duration) str() string {
 	ns := t
 
 	return match true {
-		hr > 0 { '${hr}:${min:02}:${sec:02}' }
-		min > 0 { '${min}:${sec:02}.${ms:03}' }
-		sec > 0 { '${sec}.${ms:03}s' }
-		ms > 0 { '${ms}.${us:03}ms' }
-		us > 0 { '${us}.${ns:03}us' }
-		else { '${ns}ns' }
+		hr > 0 { '${sign}${hr}:${min:02}:${sec:02}' }
+		min > 0 { '${sign}${min}:${sec:02}.${ms:03}' }
+		sec > 0 { '${sign}${sec}.${ms:03}s' }
+		ms > 0 { '${sign}${ms}.${us:03}ms' }
+		us > 0 { '${sign}${us}.${ns:03}us' }
+		else { '${sign}${ns}ns' }
 	}
 }
 
diff --git a/vlib/time/duration_test.v b/vlib/time/duration_test.v
index 9732c43ed7..66f6599b2d 100644
--- a/vlib/time/duration_test.v
+++ b/vlib/time/duration_test.v
@@ -32,6 +32,14 @@ fn test_duration_str() {
 	assert time.Duration(168 * time.hour + 5 * time.minute + 7 * time.second).str() == '168:05:07'
 }
 
+fn test_negative_duration() {
+	now := time.parse('2000-01-01 10:00:00')!
+	later := time.parse('2000-01-01 11:00:00')!
+	duration := now - later
+	assert time.Duration(-1 * time.hour) == duration
+	assert duration.str() == '-1:00:00'
+}
+
 fn test_duration_debug() {
 	assert time.Duration(1 * time.nanosecond).debug() == 'Duration: 1ns'
 	assert time.Duration(169 * time.hour + 5 * time.minute + 7 * time.second).debug() == 'Duration: 7days, 1h, 5m, 7s'