From bc611a31a5b3003ba6c05d337093f9b83e898209 Mon Sep 17 00:00:00 2001
From: Michalis Kargakis <michaliskargakis@gmail.com>
Date: Sun, 21 Dec 2014 23:03:11 +0100
Subject: [PATCH] flag: Check for Set error

Check for Set error when a boolean flag isn't explicitly given a value.

Fixes #9345

Change-Id: I97a1289f8cf27567d1a726ebe5ef167c800f357c
Reviewed-on: https://go-review.googlesource.com/1897
Reviewed-by: Andrew Gerrand <adg@golang.org>
Reviewed-by: Rob Pike <r@golang.org>
---
 src/flag/flag.go | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/flag/flag.go b/src/flag/flag.go
index 25660054a7..8c0e402e38 100644
--- a/src/flag/flag.go
+++ b/src/flag/flag.go
@@ -767,7 +767,9 @@ func (f *FlagSet) parseOne() (bool, error) {
 				return false, f.failf("invalid boolean value %q for -%s: %v", value, name, err)
 			}
 		} else {
-			fv.Set("true")
+			if err := fv.Set("true"); err != nil {
+				return false, f.failf("invalid boolean flag %s: %v", name, err)
+			}
 		}
 	} else {
 		// It must have a value, which might be the next argument.