From 030475976f3116c7b0f9868e093b3e200a6fe1a7 Mon Sep 17 00:00:00 2001
From: Joe Gregorio <jcgregorio@google.com>
Date: Sat, 5 Dec 2020 21:39:34 -0500
Subject: [PATCH] Fix Context.Value.

Before this change the added test would crash on a nil
pointer dereference because the original code would
only look in the local fileSet and not across all
the fileSets.
---
 context.go      |  5 ++++-
 context_test.go | 11 +++++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/context.go b/context.go
index 74ed51912e..65e0d1e4cb 100644
--- a/context.go
+++ b/context.go
@@ -108,7 +108,10 @@ func (c *Context) Lineage() []*Context {
 
 // Value returns the value of the flag corresponding to `name`
 func (c *Context) Value(name string) interface{} {
-	return c.flagSet.Lookup(name).Value.(flag.Getter).Get()
+	if fs := lookupFlagSet(name, c); fs != nil {
+		return fs.Lookup(name).Value.(flag.Getter).Get()
+	}
+	return nil
 }
 
 // Args returns the command line arguments associated with the context.
diff --git a/context_test.go b/context_test.go
index 61d6268452..335b071790 100644
--- a/context_test.go
+++ b/context_test.go
@@ -136,6 +136,17 @@ func TestContext_Bool(t *testing.T) {
 	expect(t, c.Bool("top-flag"), true)
 }
 
+func TestContext_Value(t *testing.T) {
+	set := flag.NewFlagSet("test", 0)
+	set.Int("myflag", 12, "doc")
+	parentSet := flag.NewFlagSet("test", 0)
+	parentSet.Int("top-flag", 13, "doc")
+	parentCtx := NewContext(nil, parentSet, nil)
+	c := NewContext(nil, set, parentCtx)
+	expect(t, c.Value("myflag"), 12)
+	expect(t, c.Value("top-flag"), 13)
+}
+
 func TestContext_Args(t *testing.T) {
 	set := flag.NewFlagSet("test", 0)
 	set.Bool("myflag", false, "doc")