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

1 files changed, 12 insertions, 0 deletions

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