html/template: clean up locking for ExecuteTemplate

R=mikesamuel, rogpeppe
CC=golang-dev
https://golang.org/cl/5448137

diff --git a/src/pkg/html/template/template.go b/src/pkg/html/template/template.go
index fa2ed18874cc9f26f73b231e18ceda987d3aa409..02e33e125ab336cf8a77b60f20aab7b3a0dee929 100644 (file)
--- a/src/pkg/html/template/template.go
+++ b/src/pkg/html/template/template.go
@@ -49,20 +49,28 @@ func (t *Template) Execute(wr io.Writer, data interface{}) (err error) {
 
 // ExecuteTemplate applies the template associated with t that has the given
 // name to the specified data object and writes the output to wr.
-func (t *Template) ExecuteTemplate(wr io.Writer, name string, data interface{}) (err error) {
+func (t *Template) ExecuteTemplate(wr io.Writer, name string, data interface{}) error {
+       tmpl, err := t.lookupAndEscapeTemplate(wr, name)
+       if err != nil {
+               return err
+       }
+       return tmpl.text.Execute(wr, data)
+}
+
+// lookupAndEscapeTemplate guarantees that the template with the given name
+// is escaped, or returns an error if it cannot be. It returns the named
+// template.
+func (t *Template) lookupAndEscapeTemplate(wr io.Writer, name string) (tmpl *Template, err error) {
        t.nameSpace.mu.Lock()
-       tmpl := t.set[name]
+       defer t.nameSpace.mu.Unlock()
+       tmpl = t.set[name]
        if (tmpl == nil) != (t.text.Lookup(name) == nil) {
                panic("html/template internal error: template escaping out of sync")
        }
        if tmpl != nil && !tmpl.escaped {
                err = escapeTemplates(tmpl, name)
        }
-       t.nameSpace.mu.Unlock()
-       if err != nil {
-               return
-       }
-       return t.text.ExecuteTemplate(wr, name, data)
+       return tmpl, err
 }
 
 // Parse parses a string into a template. Nested template definitions