add line numbers for parser errors (#7326)

parser/parser.go

@@ -65,9 +65,22 @@ var (
 	errInvalidCommand     = errors.New("command must be one of \"from\", \"license\", \"template\", \"system\", \"adapter\", \"parameter\", or \"message\"")
 )
 
+type ParserError struct {
+	LineNumber int
+	Msg        string
+}
+
+func (e *ParserError) Error() string {
+	if e.LineNumber > 0 {
+		return fmt.Sprintf("(line %d): %s", e.LineNumber, e.Msg)
+	}
+	return e.Msg
+}
+
 func ParseFile(r io.Reader) (*File, error) {
 	var cmd Command
 	var curr state
+	var currLine int = 1
 	var b bytes.Buffer
 	var role string
 
@@ -84,11 +97,18 @@ func ParseFile(r io.Reader) (*File, error) {
 			return nil, err
 		}
 
+		if isNewline(r) {
+			currLine++
+		}
+
 		next, r, err := parseRuneForState(r, curr)
 		if errors.Is(err, io.ErrUnexpectedEOF) {
 			return nil, fmt.Errorf("%w: %s", err, b.String())
 		} else if err != nil {
-			return nil, err
+			return nil, &ParserError{
+				LineNumber: currLine,
+				Msg:        err.Error(),
+			}
 		}
 
 		// process the state transition, some transitions need to be intercepted and redirected
@@ -96,7 +116,10 @@ func ParseFile(r io.Reader) (*File, error) {
 			switch curr {
 			case stateName:
 				if !isValidCommand(b.String()) {
-					return nil, errInvalidCommand
+					return nil, &ParserError{
+						LineNumber: currLine,
+						Msg:        errInvalidCommand.Error(),
+					}
 				}
 
 				// next state sometimes depends on the current buffer value
@@ -117,7 +140,10 @@ func ParseFile(r io.Reader) (*File, error) {
 				cmd.Name = b.String()
 			case stateMessage:
 				if !isValidMessageRole(b.String()) {
-					return nil, errInvalidMessageRole
+					return nil, &ParserError{
+						LineNumber: currLine,
+						Msg:        errInvalidMessageRole.Error(),
+					}
 				}
 
 				role = b.String()