Avoid multiple locks for shortcode template

Fixes #1600

diff --git a/hugolib/shortcode.go b/hugolib/shortcode.go
index 4d3037dc8b277abfa4f1e7d0ae49be62e19f9c61..a306023a71adc085ce8eb366ea64827b2fedfebc 100644 (file)
--- a/hugolib/shortcode.go
+++ b/hugolib/shortcode.go
@@ -160,21 +160,24 @@ var isInnerShortcodeCache = struct {
 // to avoid potential costly look-aheads for closing tags we look inside the template itself
 // we could change the syntax to self-closing tags, but that would make users cry
 // the value found is cached
-func isInnerShortcode(t *template.Template) bool {
+func isInnerShortcode(t *template.Template) (bool, error) {
        isInnerShortcodeCache.RLock()
        m, ok := isInnerShortcodeCache.m[t.Name()]
        isInnerShortcodeCache.RUnlock()
 
        if ok {
-               return m
+               return m, nil
        }
 
        isInnerShortcodeCache.Lock()
        defer isInnerShortcodeCache.Unlock()
+       if t.Tree == nil {
+               return false, errors.New("Template failed to compile")
+       }
        match, _ := regexp.MatchString("{{.*?\\.Inner.*?}}", t.Tree.Root.String())
        isInnerShortcodeCache.m[t.Name()] = match
 
-       return match
+       return match, nil
 }
 
 func createShortcodePlaceholder(id int) string {
@@ -344,14 +347,11 @@ Loop:
                                return sc, fmt.Errorf("Unable to locate template for shortcode '%s' in page %s", sc.name, p.BaseFileName())
                        }
 
-                       // TODO(bep) Refactor/rename this lock strategy
-                       isInnerShortcodeCache.RLock()
-                       if tmpl.Tree == nil {
-                               isInnerShortcodeCache.RUnlock()
-                               return sc, fmt.Errorf("Template for shortcode '%s' failed to compile for page '%s'", sc.name, p.BaseFileName())
+                       var err error
+                       isInner, err = isInnerShortcode(tmpl)
+                       if err != nil {
+                               return sc, fmt.Errorf("Failed to handle template for shortcode '%s' for page '%s': %s", sc.name, p.BaseFileName(), err)
                        }
-                       isInnerShortcodeCache.RUnlock()
-                       isInner = isInnerShortcode(tmpl)
 
                case tScParam:
                        if !pt.isValueNext() {
@@ -523,9 +523,6 @@ func renderShortcodeWithPage(tmpl *template.Template, data *ShortcodeWithPage) s
        buffer := bp.GetBuffer()
        defer bp.PutBuffer(buffer)
 
-       // TODO(bep) Refactor/rename this lock strategy
-       isInnerShortcodeCache.Lock()
-       defer isInnerShortcodeCache.Unlock()
        err := tmpl.Execute(buffer, data)
        if err != nil {
                jww.ERROR.Println("error processing shortcode", tmpl.Name(), "\n ERR:", err)