argparse: print positional arg details in usage

Add a printout of positional args (name, description, '(optional)' or not)
in the 'Usage()' string.

Signed-off-by: Victoria Dye <[email protected]>

Author: vdye

internal/argparse/argparse.go

@@ -61,7 +61,7 @@ func NewArgParser(logger log.TraceLogger, usageString string) *argParser {
 			fmt.Fprint(out, "\n")
 		}
 
-		// Print subcommands (if any)
+		// Print subcommands or positional args (if any)
 		if len(a.subcommands) > 0 {
 			if a.isTopLevel {
 				fmt.Fprintln(out, "Commands:")
@@ -70,6 +70,10 @@ func NewArgParser(logger log.TraceLogger, usageString string) *argParser {
 			}
 			a.printSubcommands()
 			fmt.Fprint(out, "\n")
+		} else if len(a.positionalArgs) > 0 {
+			fmt.Fprintln(out, "Positional arguments:")
+			a.printPositionalArgs()
+			fmt.Fprint(out, "\n")
 		}
 	}
 
@@ -94,6 +98,21 @@ func (a *argParser) Subcommand(subcommand Subcommand) {
 	a.subcommands[subcommand.Name()] = subcommand
 }
 
+func (a *argParser) printPositionalArgs() {
+	out := a.FlagSet.Output()
+	for _, arg := range a.positionalArgs {
+		optionalStr := ""
+		if !arg.required {
+			optionalStr = "(optional) "
+		}
+		fmt.Fprintf(out, "  %s\n    \t%s%s\n",
+			arg.name,
+			optionalStr,
+			strings.ReplaceAll(strings.TrimSpace(arg.description), "\n", "\n    \t"),
+		)
+	}
+}
+
 func (a *argParser) PositionalStringVar(name string, description string, arg *string, required bool) {
 	a.positionalArgs = append(a.positionalArgs, &positionalArg{
 		name:        name,