From acc622e5fb6f273c26946ded483aa813bebdcee9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?P=C3=A9ter=20Szil=C3=A1gyi?= <peterke@gmail.com>
Date: Wed, 11 Jan 2017 14:38:54 +0200
Subject: [PATCH] Invalidate context.setFlags cache on modification.

---
 context.go      | 2 ++
 context_test.go | 4 ++++
 2 files changed, 6 insertions(+)

diff --git a/context.go b/context.go
index cb89e92..db94191 100644
--- a/context.go
+++ b/context.go
@@ -39,11 +39,13 @@ func (c *Context) NumFlags() int {
 
 // Set sets a context flag to a value.
 func (c *Context) Set(name, value string) error {
+	c.setFlags = nil
 	return c.flagSet.Set(name, value)
 }
 
 // GlobalSet sets a context flag to a value on the global flagset
 func (c *Context) GlobalSet(name, value string) error {
+	globalContext(c).setFlags = nil
 	return globalContext(c).flagSet.Set(name, value)
 }
 
diff --git a/context_test.go b/context_test.go
index a1ab05b..7acca10 100644
--- a/context_test.go
+++ b/context_test.go
@@ -375,8 +375,10 @@ func TestContext_Set(t *testing.T) {
 	set.Int("int", 5, "an int")
 	c := NewContext(nil, set, nil)
 
+	expect(t, c.IsSet("int"), false)
 	c.Set("int", "1")
 	expect(t, c.Int("int"), 1)
+	expect(t, c.IsSet("int"), true)
 }
 
 func TestContext_GlobalSet(t *testing.T) {
@@ -393,7 +395,9 @@ func TestContext_GlobalSet(t *testing.T) {
 	expect(t, c.Int("int"), 1)
 	expect(t, c.GlobalInt("int"), 5)
 
+	expect(t, c.GlobalIsSet("int"), false)
 	c.GlobalSet("int", "1")
 	expect(t, c.Int("int"), 1)
 	expect(t, c.GlobalInt("int"), 1)
+	expect(t, c.GlobalIsSet("int"), true)
 }