From 1f1166ebf178838ab1cc0b692a2494d74bc46a61 Mon Sep 17 00:00:00 2001
From: Laurent Demailly <ldemailly@gmail.com>
Date: Thu, 11 Sep 2025 14:13:40 -0700
Subject: [PATCH] Add test and fix bug in default help/printing of duration

---
 duration.go      |  3 +--
 duration_test.go | 32 ++++++++++++++++++++++++++++++++
 2 files changed, 33 insertions(+), 2 deletions(-)

diff --git a/duration.go b/duration.go
index 826ef5c..1df93d2 100644
--- a/duration.go
+++ b/duration.go
@@ -213,9 +213,8 @@ func FlagVar(p *time.Duration, name string, value time.Duration, usage string) {
 
 // FlagSet is like [FlagVar] but for the specified flag set. Replacement for [flag.FlagSet.DurationVar].
 func FlagSetVar(fs *flag.FlagSet, p *time.Duration, name string, value time.Duration, usage string) {
-	d := Duration(value)
+	*p = value
 	fs.Var((*Duration)(p), name, usage)
-	*p = time.Duration(d)
 }
 
 // NextTime takes a partially parsed time.Time (without date) and returns the time in the future
diff --git a/duration_test.go b/duration_test.go
index fd3cc2a..198c4b0 100644
--- a/duration_test.go
+++ b/duration_test.go
@@ -1,8 +1,10 @@
 package duration_test
 
 import (
+	"bytes"
 	"flag"
 	"fmt"
+	"strings"
 	"testing"
 	"time"
 
@@ -185,3 +187,33 @@ func ExampleFlag() {
 	// After set: 1d1h
 	// After set (dereferenced): 25h0m0s
 }
+
+func TestHelpShowsDefault(t *testing.T) {
+	fs := flag.NewFlagSet("test", flag.ContinueOnError)
+	var buf bytes.Buffer
+	fs.SetOutput(&buf)
+	var d time.Duration
+	duration.FlagSetVar(fs, &d, "duration", 1*duration.Day+3*time.Hour, "example of duration flag with days support")
+	// print defaults
+	fs.PrintDefaults()
+	// check:
+	out := buf.String()
+	if !strings.Contains(out, "(default 1d3h)") {
+		t.Errorf("expected help to include default 1d3h, got:\n%s", out)
+	}
+}
+
+func TestHelpNotShowingDefaultZeroValue(t *testing.T) {
+	fs := flag.NewFlagSet("test", flag.ContinueOnError)
+	var buf bytes.Buffer
+	fs.SetOutput(&buf)
+	var d time.Duration
+	duration.FlagSetVar(fs, &d, "duration", 0, "example of duration flag with days support")
+	// print defaults
+	fs.PrintDefaults()
+	// check:
+	out := buf.String()
+	if strings.Contains(out, "(default") {
+		t.Errorf("expected help to not include default for zero value, got:\n%s", out)
+	}
+}