Fixed a crash case and added an exclude optional parameter

cmd/lll/main.go

@@ -18,6 +18,7 @@ var args struct {
 	SkipList  []string `arg:"-s,env,help:list of dirs to skip"`
 	Vendor    bool     `arg:"env,help:check files in vendor directory"`
 	Files     bool     `arg:"help:read file names from stdin one at each line"`
+	Exclude     string     `arg:"env,help:exclude lines with this substring"`
 }
 
 func main() {
@@ -38,7 +39,7 @@ func main() {
 	if args.Files {
 		s := bufio.NewScanner(os.Stdin)
 		for s.Scan() {
-			err := lll.ProcessFile(os.Stdout, s.Text(), args.MaxLength)
+			err := lll.ProcessFile(os.Stdout, s.Text(), args.MaxLength, args.Exclude)
 			if err != nil {
 				fmt.Fprintf(os.Stderr, "Error processing file: %s\n", err)
 			}
@@ -49,12 +50,16 @@ func main() {
 	// Otherwise, walk the inputs recursively
 	for _, d := range args.Input {
 		err := filepath.Walk(d, func(p string, i os.FileInfo, e error) error {
+			if e != nil {
+				return e
+			}
+
 			skip, ret := lll.ShouldSkip(p, i.IsDir(), e, args.SkipList, args.GoOnly)
 			if skip {
 				return ret
 			}
 
-			err := lll.ProcessFile(os.Stdout, p, args.MaxLength)
+			err := lll.ProcessFile(os.Stdout, p, args.MaxLength, args.Exclude)
 			return err
 		})
 

lll.go

@@ -54,7 +54,7 @@ func ShouldSkip(path string, isDir bool, err error,
 
 // ProcessFile checks all lines in the file and writes an error if the line
 // length is greater than MaxLength.
-func ProcessFile(w io.Writer, path string, maxLength int) error {
+func ProcessFile(w io.Writer, path string, maxLength int, exclude string) error {
 	f, err := os.Open(path)
 	if err != nil {
 		return err
@@ -66,16 +66,20 @@ func ProcessFile(w io.Writer, path string, maxLength int) error {
 		}
 	}()
 
-	return Process(f, w, path, maxLength)
+	return Process(f, w, path, maxLength, exclude)
 }
 
 // Process checks all lines in the reader and writes an error if the line length
 // is greater than MaxLength.
-func Process(r io.Reader, w io.Writer, path string, maxLength int) error {
+func Process(r io.Reader, w io.Writer, path string, maxLength int, exclude string) error {
 	l := 1
 	s := bufio.NewScanner(r)
 	for s.Scan() {
-		c := utf8.RuneCountInString(s.Text())
+		t := s.Text()
+		if len(exclude) != 0 && strings.Contains(t, exclude) {
+			continue
+		}
+		c := utf8.RuneCountInString(t)
 		if c > maxLength {
 			fmt.Fprintf(w, "%s:%d: line is %d characters\n", path, l, c)
 		}