cli.go: fixed an out-of-bound error on cli.argSpecs array

cli.go

@@ -163,6 +163,7 @@ func (cli *CliParser) Parse() (err error) {
 
 	cli.addHelpAndVersion()
 
+	// first parse options and collect argument in the args array
 	skipNext := false
 	for i, arg = range cli.cliArgs[1:] {
 		if skipNext {
@@ -182,12 +183,16 @@ func (cli *CliParser) Parse() (err error) {
 			}
 		}
 	}
+
+	// then parse collected arguments
 	if err == nil {
-		var argSpec argSpec
-		var n, specIndex int
+		var n int
 		i = 0
 
-		for specIndex, argSpec = range cli.argSpecs {
+		// acquire arguments as required by the argSpecs
+		specIndex := -1
+		for index, argSpec := range cli.argSpecs {
+			specIndex = index
 			if n, err = argSpec.parse(cli, specIndex, args, i); err != nil {
 				break
 			}
@@ -196,16 +201,22 @@ func (cli *CliParser) Parse() (err error) {
 				break
 			}
 		}
+
+		// check if there are remaining arg-specs that require a value
 		if err == nil {
 			if i < len(args) {
 				err = fmt.Errorf("too many arguments: %d allowed", i)
 			} else {
 				specIndex++
-				for _, spec := range cli.argSpecs[specIndex:] {
-					if !spec.getBase().required {
-						specIndex++
+				if specIndex < len(cli.argSpecs) {
+					// skip all non required args
+					for _, spec := range cli.argSpecs[specIndex:] {
+						if !spec.getBase().required {
+							specIndex++
+						}
 					}
 				}
+				// return error if there are remaining arg-specs that require a value
 				if specIndex < len(cli.argSpecs) {
 					err = errTooFewArguments(len(cli.argSpecs))
 				}