From 2d3fed9f2992a11ab76601484a735d5500d84dba Mon Sep 17 00:00:00 2001
From: Ryo Nihei <nihei.dev@gmail.com>
Date: Sat, 17 Jul 2021 13:41:44 +0900
Subject: Improve syntax error messages

- Add a source file name to error messages.
- Add a line that an error occurred at to error messages.
---
 cmd/vartan/parse.go | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

(limited to 'cmd/vartan/parse.go')

diff --git a/cmd/vartan/parse.go b/cmd/vartan/parse.go
index 8089c5e..ef22ff3 100644
--- a/cmd/vartan/parse.go
+++ b/cmd/vartan/parse.go
@@ -28,6 +28,24 @@ func init() {
 }
 
 func runParse(cmd *cobra.Command, args []string) (retErr error) {
+	defer func() {
+		v := recover()
+		if v != nil {
+			err, ok := v.(error)
+			if !ok {
+				retErr = fmt.Errorf("an unexpected error occurred: %v\n", v)
+				fmt.Fprintln(os.Stderr, retErr)
+				return
+			}
+
+			retErr = err
+		}
+
+		if retErr != nil {
+			fmt.Fprintln(os.Stderr, retErr)
+		}
+	}()
+
 	cgram, err := readCompiledGrammar(args[0])
 	if err != nil {
 		return fmt.Errorf("Cannot read a compiled grammar: %w", err)
-- 
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