add FailSubcommand, WriteUsageForSubcommand, WriteHelpForSubcommand

1 files changed, 94 insertions, 1 deletions

diff --git a/example_test.go b/example_test.go
index 2e9b875..2b7ce00 100644
--- a/example_test.go
+++ b/example_test.go
@@ -250,7 +250,7 @@ func Example_helpTextWithSubcommand() {
 }
 
 // This example shows the usage string generated by go-arg when using subcommands
-func Example_helpTextForSubcommand() {
+func Example_helpTextWhenUsingSubcommand() {
 	// These are the args you would pass in on the command line
 	os.Args = split("./example get --help")
 
@@ -286,6 +286,99 @@ func Example_helpTextForSubcommand() {
 	//   --help, -h             display this help and exit
 }
 
+// This example shows how to print help for an explicit subcommand
+func Example_writeHelpForSubcommand() {
+	// These are the args you would pass in on the command line
+	os.Args = split("./example get --help")
+
+	type getCmd struct {
+		Item string `arg:"positional" help:"item to fetch"`
+	}
+
+	type listCmd struct {
+		Format string `help:"output format"`
+		Limit  int
+	}
+
+	var args struct {
+		Verbose bool
+		Get     *getCmd  `arg:"subcommand" help:"fetch an item and print it"`
+		List    *listCmd `arg:"subcommand" help:"list available items"`
+	}
+
+	// This is only necessary when running inside golang's runnable example harness
+	osExit = func(int) {}
+	stdout = os.Stdout
+
+	p, err := NewParser(Config{}, &args)
+	if err != nil {
+		fmt.Println(err)
+		os.Exit(1)
+	}
+
+	err = p.WriteHelpForSubcommand(os.Stdout, "list")
+	if err != nil {
+		fmt.Println(err)
+		os.Exit(1)
+	}
+
+	// output:
+	// Usage: example list [--format FORMAT] [--limit LIMIT]
+	//
+	// Options:
+	//   --format FORMAT        output format
+	//   --limit LIMIT
+	//
+	// Global options:
+	//   --verbose
+	//   --help, -h             display this help and exit
+}
+
+// This example shows how to print help for a subcommand that is nested several levels deep
+func Example_writeHelpForSubcommandNested() {
+	// These are the args you would pass in on the command line
+	os.Args = split("./example get --help")
+
+	type mostNestedCmd struct {
+		Item string
+	}
+
+	type nestedCmd struct {
+		MostNested *mostNestedCmd `arg:"subcommand"`
+	}
+
+	type topLevelCmd struct {
+		Nested *nestedCmd `arg:"subcommand"`
+	}
+
+	var args struct {
+		TopLevel *topLevelCmd `arg:"subcommand"`
+	}
+
+	// This is only necessary when running inside golang's runnable example harness
+	osExit = func(int) {}
+	stdout = os.Stdout
+
+	p, err := NewParser(Config{}, &args)
+	if err != nil {
+		fmt.Println(err)
+		os.Exit(1)
+	}
+
+	err = p.WriteHelpForSubcommand(os.Stdout, "toplevel", "nested", "mostnested")
+	if err != nil {
+		fmt.Println(err)
+		os.Exit(1)
+	}
+
+	// output:
+	// Usage: example toplevel nested mostnested [--item ITEM]
+	//
+	// Options:
+	//   --item ITEM
+	//   --help, -h             display this help and exit
+}
+
 // This example shows the error string generated by go-arg when an invalid option is provided
 func Example_errorText() {
 	// These are the args you would pass in on the command line