From d4cc703210ff08d7bc4f73bfbec1e51eda29a5a4 Mon Sep 17 00:00:00 2001
From: "Wlazlo, Matt" <matt.wlazlo@team.telstra.com>
Date: Fri, 13 Apr 2018 14:46:24 +1000
Subject: Custom parsers implementing encoding.TextMarshaler() can have default
 values printed via --help

---
 README.md | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

(limited to 'README.md')

diff --git a/README.md b/README.md
index 18dc556..f3d1bfc 100644
--- a/README.md
+++ b/README.md
@@ -265,15 +265,33 @@ func (n *NameDotName) UnmarshalText(b []byte) error {
 	return nil
 }
 
+// optional, implement in case you want to use defaults
+func (n *NameDotName) MarshalText() (text []byte, err error) {
+	text = []byte(fmt.Sprintf("%s.%s", n.Head, n.Tail))
+	return
+}
+
 func main() {
 	var args struct {
 		Name *NameDotName
 	}
+	// set default
+	args.Name = &NameDotName{"file", "txt"}
 	arg.MustParse(&args)
 	fmt.Printf("%#v\n", args.Name)
 }
 ```
 ```shell
+$ ./example --help
+Usage: test [--name NAME]
+
+Options:
+  --name NAME [default: file.txt]
+  --help, -h             display this help and exit
+
+$ ./example
+&main.NameDotName{Head:"file", Tail:"txt"}
+
 $ ./example --name=foo.bar
 &main.NameDotName{Head:"foo", Tail:"bar"}
 
-- 
cgit v1.2.3


From 51337ded775c91dc26574d7d2dc2e493cf416138 Mon Sep 17 00:00:00 2001
From: "Wlazlo, Matt" <matt.wlazlo@team.telstra.com>
Date: Mon, 16 Apr 2018 11:07:48 +1000
Subject: fixed example comment, test coverage issue

---
 README.md     |  2 +-
 usage_test.go | 37 +++++++++++++++++++++++++++++++++++++
 2 files changed, 38 insertions(+), 1 deletion(-)

(limited to 'README.md')

diff --git a/README.md b/README.md
index f3d1bfc..e8b62a4 100644
--- a/README.md
+++ b/README.md
@@ -265,7 +265,7 @@ func (n *NameDotName) UnmarshalText(b []byte) error {
 	return nil
 }
 
-// optional, implement in case you want to use defaults
+// optional: implement in case you want to display a default value in the usage string
 func (n *NameDotName) MarshalText() (text []byte, err error) {
 	text = []byte(fmt.Sprintf("%s.%s", n.Head, n.Tail))
 	return
diff --git a/usage_test.go b/usage_test.go
index 4aa2f24..4f179f0 100644
--- a/usage_test.go
+++ b/usage_test.go
@@ -9,6 +9,7 @@ import (
 	"github.com/stretchr/testify/require"
 	"strings"
 	"fmt"
+	"errors"
 )
 
 type NameDotName struct {
@@ -85,6 +86,42 @@ Options:
 	assert.Equal(t, expectedHelp, help.String())
 }
 
+type MyEnum int
+
+func (n *MyEnum) UnmarshalText(b []byte) error {
+	b = []byte("Hello")
+	return nil
+}
+
+func (n *MyEnum) MarshalText() (text []byte, err error) {
+	s := "There was a problem"
+	text = []byte(s)
+	err = errors.New(s)
+	return
+}
+
+func TestUsageError(t *testing.T) {
+	expectedHelp := `Usage: example [--name NAME]
+
+Options:
+  --name NAME [default: error: There was a problem]
+  --help, -h             display this help and exit
+`
+	var args struct {
+		Name *MyEnum
+	}
+	v := MyEnum(42)
+	args.Name = &v
+	p, err := NewParser(Config{"example"}, &args)
+
+	// NB: some might might expect there to be an error here
+	require.NoError(t, err)
+
+	var help bytes.Buffer
+	p.WriteHelp(&help)
+	assert.Equal(t, expectedHelp, help.String())
+}
+
 func TestUsageLongPositionalWithHelp_legacyForm(t *testing.T) {
 	expectedHelp := `Usage: example VERYLONGPOSITIONALWITHHELP
 
-- 
cgit v1.2.3