html/template: attach functions to namespace

The text/template functions are stored in a data structure shared by
all related templates, so do the same with the original, unwrapped,
functions on the html/template side.

For #39807
Fixes #43295

Change-Id: I9f64a0a601f1151c863a2833b5be2baf649b6cef
Reviewed-on: https://go-review.googlesource.com/c/go/+/279492
Trust: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Emmanuel Odeke <emmanuel@orijtech.com>

1 files changed, 20 insertions, 0 deletions

diff --git a/src/html/template/exec_test.go b/src/html/template/exec_test.go
index eb00824260..cd6b78a1a9 100644
--- a/src/html/template/exec_test.go
+++ b/src/html/template/exec_test.go
@@ -1776,3 +1776,23 @@ func TestRecursiveExecute(t *testing.T) {
 		t.Fatal(err)
 	}
 }
+
+// Issue 43295.
+func TestTemplateFuncsAfterClone(t *testing.T) {
+	s := `{{ f . }}`
+	want := "test"
+	orig := New("orig").Funcs(map[string]interface{}{
+		"f": func(in string) string {
+			return in
+		},
+	}).New("child")
+
+	overviewTmpl := Must(Must(orig.Clone()).Parse(s))
+	var out strings.Builder
+	if err := overviewTmpl.Execute(&out, want); err != nil {
+		t.Fatal(err)
+	}
+	if got := out.String(); got != want {
+		t.Fatalf("got %q; want %q", got, want)
+	}
+}