diff --git a/src/html/template/clone_test.go b/src/html/template/clone_test.go
index d7c62fa399..069064c98b 100644
--- a/src/html/template/clone_test.go
+++ b/src/html/template/clone_test.go
@@ -8,6 +8,7 @@ import (
"bytes"
"errors"
"io/ioutil"
+ "sync"
"testing"
"text/template/parse"
)
@@ -194,3 +195,37 @@ func TestFuncMapWorksAfterClone(t *testing.T) {
t.Errorf("clone error message mismatch want %q got %q", wantErr, gotErr)
}
}
+
+// https://golang.org/issue/16101
+func TestTemplateCloneExecuteRace(t *testing.T) {
+ const (
+ input = `{{block "a" .}}a{{end}}{{block "b" .}}b{{end}}`
+ overlay = `{{define "b"}}A{{end}}`
+ )
+ outer := Must(New("outer").Parse(input))
+ tmpl := Must(Must(outer.Clone()).Parse(overlay))
+
+ var wg sync.WaitGroup
+ for i := 0; i < 10; i++ {
+ wg.Add(1)
+ go func() {
+ defer wg.Done()
+ for i := 0; i < 100; i++ {
+ if err := tmpl.Execute(ioutil.Discard, "data"); err != nil {
+ panic(err)
+ }
+ }
+ }()
+ }
+ wg.Wait()
+}
+
+func TestTemplateCloneLookup(t *testing.T) {
+ // Template.escape makes an assumption that the template associated
+ // with t.Name() is t. Check that this holds.
+ tmpl := Must(New("x").Parse("a"))
+ tmpl = Must(tmpl.Clone())
+ if tmpl.Lookup(tmpl.Name()) != tmpl {
+ t.Error("after Clone, tmpl.Lookup(tmpl.Name()) != tmpl")
+ }
+}
diff --git a/src/html/template/template.go b/src/html/template/template.go
index 063e46d6bf..d5e195ff69 100644
--- a/src/html/template/template.go
+++ b/src/html/template/template.go
@@ -240,6 +240,9 @@ func (t *Template) Clone() (*Template, error) {
ret.set[ret.Name()] = ret
for _, x := range textClone.Templates() {
name := x.Name()
+ if name == ret.Name() {
+ continue
+ }
src := t.set[name]
if src == nil || src.escapeErr != nil {
return nil, fmt.Errorf("html/template: cannot Clone %q after it has executed", t.Name())