Merge pull request #8 from teru01/feature/error-logs

improve stack trace logs with %+v

errors.go

@@ -128,7 +128,15 @@ func (x *Error) Format(s fmt.State, verb rune) {
 	case 'v':
 		if s.Flag('+') {
 			_, _ = io.WriteString(s, x.Error())
-			x.st.Format(s, verb)
+			var c *Error
+			for c = x; c.Unwrap() != nil; {
+				cause, ok := c.Unwrap().(*Error)
+				if !ok {
+					break
+				}
+				c = cause
+			}
+			c.st.Format(s, verb)
 			return
 		}
 		fallthrough

examples/stacktrace_print/main.go

@@ -1,21 +1,26 @@
 package main
 
 import (
+	"errors"
 	"log"
-	"os"
 
 	"github.com/m-mizutani/goerr"
 )
 
-func someAction(fname string) error {
-	if _, err := os.Open(fname); err != nil {
-		return goerr.Wrap(err, "failed to open file")
-	}
-	return nil
+func nestedAction2() error {
+	return errors.New("fatal error in the nested action2")
+}
+
+func nestedAction() error {
+	return goerr.Wrap(nestedAction2(), "nestedAction2 failed")
+}
+
+func someAction() error {
+	return goerr.Wrap(nestedAction(), "nestedAction failed")
 }
 
 func main() {
-	if err := someAction("no_such_file.txt"); err != nil {
+	if err := someAction(); err != nil {
 		log.Fatalf("%+v", err)
 	}
 }