print help and usage at subcommand level if necessary

1 files changed, 86 insertions, 3 deletions

diff --git a/example_test.go b/example_test.go
index eb8d315..b58085f 100644
--- a/example_test.go
+++ b/example_test.go
@@ -104,7 +104,7 @@ func Example_multipleMixed() {
 }
 
 // This example shows the usage string generated by go-arg
-func Example_usageString() {
+func Example_helpText() {
 	// These are the args you would pass in on the command line
 	os.Args = split("./example --help")
 
@@ -136,8 +136,8 @@ func Example_usageString() {
 	//   --help, -h             display this help and exit
 }
 
-// This example shows the usage string generated by go-arg
-func Example_usageStringWithSubcommand() {
+// This example shows the usage string generated by go-arg when using subcommands
+func Example_helpTextWithSubcommand() {
 	// These are the args you would pass in on the command line
 	os.Args = split("./example --help")
 
@@ -172,3 +172,86 @@ func Example_usageStringWithSubcommand() {
 	//   get                    fetch an item and print it
 	//   list                   list available items
 }
+
+// This example shows the usage string generated by go-arg when using subcommands
+func Example_helpTextForSubcommand() {
+	// 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) {}
+
+	MustParse(&args)
+
+	// output:
+	// Usage: example get ITEM
+	//
+	// Positional arguments:
+	//   ITEM                   item to fetch
+	//
+	// Options:
+	//   --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
+	os.Args = split("./example --optimize INVALID")
+
+	var args struct {
+		Input    string   `arg:"positional"`
+		Output   []string `arg:"positional"`
+		Verbose  bool     `arg:"-v" help:"verbosity level"`
+		Dataset  string   `help:"dataset to use"`
+		Optimize int      `arg:"-O,help:optimization level"`
+	}
+
+	// This is only necessary when running inside golang's runnable example harness
+	osExit = func(int) {}
+	stderr = os.Stdout
+
+	MustParse(&args)
+
+	// output:
+	// Usage: example [--verbose] [--dataset DATASET] [--optimize OPTIMIZE] INPUT [OUTPUT [OUTPUT ...]]
+	// error: error processing --optimize: strconv.ParseInt: parsing "INVALID": invalid syntax
+}
+
+// This example shows the error string generated by go-arg when an invalid option is provided
+func Example_errorTextForSubcommand() {
+	// These are the args you would pass in on the command line
+	os.Args = split("./example get --count INVALID")
+
+	type getCmd struct {
+		Count int
+	}
+
+	var args struct {
+		Get *getCmd `arg:"subcommand"`
+	}
+
+	// This is only necessary when running inside golang's runnable example harness
+	osExit = func(int) {}
+	stderr = os.Stdout
+
+	MustParse(&args)
+
+	// output:
+	// Usage: example get [--count COUNT]
+	// error: error processing --count: strconv.ParseInt: parsing "INVALID": invalid syntax
+}