From 1cd78eedd092c9ec10f1b5c626b8bcd0298e065f Mon Sep 17 00:00:00 2001
From: Rob Pike <r@golang.org>
Date: Sat, 18 Oct 2014 11:22:05 -0700
Subject: [PATCH] text/template: fix bug in pipelined variadics Simple bug in
 argument processing: The final arg may be the pipeline value, in which case
 it gets bound to the fixed argument section. The code got that wrong. Easy to
 fix.

Fixes #8950.

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/161750043
---
 src/text/template/exec.go      |  2 +-
 src/text/template/exec_test.go | 12 ++++++++++++
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/src/text/template/exec.go b/src/text/template/exec.go
index f6eed662b7..b00e10c7e4 100644
--- a/src/text/template/exec.go
+++ b/src/text/template/exec.go
@@ -546,7 +546,7 @@ func (s *state) evalCall(dot, fun reflect.Value, node parse.Node, name string, a
 	argv := make([]reflect.Value, numIn)
 	// Args must be evaluated. Fixed args first.
 	i := 0
-	for ; i < numFixed; i++ {
+	for ; i < numFixed && i < len(args); i++ {
 		argv[i] = s.evalArg(dot, typ.In(i), args[i])
 	}
 	// Now the ... args.
diff --git a/src/text/template/exec_test.go b/src/text/template/exec_test.go
index e2cf2d3705..69c213ed24 100644
--- a/src/text/template/exec_test.go
+++ b/src/text/template/exec_test.go
@@ -893,6 +893,18 @@ func TestMessageForExecuteEmpty(t *testing.T) {
 	}
 }
 
+func TestFinalForPrintf(t *testing.T) {
+	tmpl, err := New("").Parse(`{{"x" | printf}}`)
+	if err != nil {
+		t.Fatal(err)
+	}
+	var b bytes.Buffer
+	err = tmpl.Execute(&b, 0)
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
 type cmpTest struct {
 	expr  string
 	truth string
-- 
2.50.0