Merge pull request #13 from walle/show_builtin

Add built ins to options in help output

parse.go

@@ -19,6 +19,7 @@ type spec struct {
 	positional bool
 	help       string
 	wasPresent bool
+	isBool     bool
 }
 
 // ErrHelp indicates that -h or --help were provided
@@ -100,6 +101,11 @@ func NewParser(dests ...interface{}) (*Parser, error) {
 				return nil, fmt.Errorf("%s.%s: %s fields are not supported", t.Name(), field.Name, scalarType.Kind())
 			}
 
+			// Specify that it is a bool for usage
+			if scalarType.Kind() == reflect.Bool {
+				spec.isBool = true
+			}
+
 			// Look at the tag
 			if tag != "" {
 				for _, key := range strings.Split(tag, ",") {

usage.go

@@ -5,7 +5,6 @@ import (
 	"io"
 	"os"
 	"path/filepath"
-	"reflect"
 	"strings"
 )
 
@@ -78,10 +77,17 @@ func (p *Parser) WriteHelp(w io.Writer) {
 	}
 
 	// write the list of options
-	if len(options) > 0 {
 	fmt.Fprint(w, "\noptions:\n")
-		const colWidth = 25
 	for _, spec := range options {
+		printOption(w, spec)
+	}
+
+	// write the list of built in options
+	printOption(w, &spec{isBool: true, long: "help", short: "h", help: "display this help and exit"})
+}
+
+func printOption(w io.Writer, spec *spec) {
+	const colWidth = 25
 	left := "  " + synopsis(spec, "--"+spec.long)
 	if spec.short != "" {
 		left += ", " + synopsis(spec, "-"+spec.short)
@@ -96,12 +102,10 @@ func (p *Parser) WriteHelp(w io.Writer) {
 		fmt.Fprint(w, spec.help)
 	}
 	fmt.Fprint(w, "\n")
-		}
-	}
 }
 
 func synopsis(spec *spec, form string) string {
-	if spec.dest.Kind() == reflect.Bool {
+	if spec.isBool {
 		return form
 	}
 	return form + " " + strings.ToUpper(spec.long)

usage_test.go

@@ -23,6 +23,7 @@ options:
   --dataset DATASET      dataset to use
   --optimize OPTIMIZE, -O OPTIMIZE
                          optimization level
+  --help, -h             display this help and exit
 `
 	var args struct {
 		Input    string   `arg:"positional"`