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Add test and fix bug in default help/printing of duration #3

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ldemailly merged 1 commit into from
Sep 11, 2025
Merged

Add test and fix bug in default help/printing of duration #3

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3 changes: 1 addition & 2 deletions duration.go
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Original file line number Diff line number Diff line change
Expand Up @@ -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
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Copilot AI Sep 11, 2025

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The fix creates a potential issue where *p is set to the raw time.Duration value before registering the flag. This means the flag's String() method will return the standard Go duration format (e.g., '27h0m0s') instead of the human-readable format (e.g., '1d3h') for default values in help text. Consider creating a Duration instance first to ensure proper formatting: d := Duration(value); *p = time.Duration(d); fs.Var((*Duration)(p), name, usage)

Suggested change
*p = value
d := Duration(value)
*p = time.Duration(d)

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@ldemailly ldemailly Sep 11, 2025

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this is the fix actually - need value indeed to be set for default to work

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
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32 changes: 32 additions & 0 deletions duration_test.go
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Original file line number Diff line number Diff line change
@@ -1,8 +1,10 @@
package duration_test

import (
"bytes"
"flag"
"fmt"
"strings"
"testing"
"time"

Expand Down Expand Up @@ -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)
}
}
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