html: Hide excluded headlines from TOC

emacs org mode did it first

org/headline.go

@@ -89,6 +89,17 @@ func (h Headline) ID() string {
 	return fmt.Sprintf("headline-%d", h.Index)
 }
 
+func (h Headline) IsExcluded(d *Document) bool {
+	for _, excludedTag := range strings.Fields(d.Get("EXCLUDE_TAGS")) {
+		for _, tag := range h.Tags {
+			if tag == excludedTag {
+				return true
+			}
+		}
+	}
+	return false
+}
+
 func (parent *Section) add(current *Section) {
 	if parent.Headline == nil || parent.Headline.Lvl < current.Headline.Lvl {
 		parent.Children = append(parent.Children, current)

org/html_writer.go

@@ -227,7 +227,7 @@ func (w *HTMLWriter) WriteOutline(d *Document, maxLvl int) {
 }
 
 func (w *HTMLWriter) writeSection(section *Section, maxLvl int) {
-	if maxLvl != 0 && section.Headline.Lvl > maxLvl {
+	if (maxLvl != 0 && section.Headline.Lvl > maxLvl) || section.Headline.IsExcluded(w.document) {
 		return
 	}
 	// NOTE: To satisfy hugo ExtractTOC() check we cannot use `<li>\n` here. Doesn't really matter, just a note.
@@ -250,12 +250,8 @@ func (w *HTMLWriter) writeSection(section *Section, maxLvl int) {
 }
 
 func (w *HTMLWriter) WriteHeadline(h Headline) {
-	for _, excludeTag := range strings.Fields(w.document.Get("EXCLUDE_TAGS")) {
-		for _, tag := range h.Tags {
-			if excludeTag == tag {
-				return
-			}
-		}
+	if h.IsExcluded(w.document) {
+		return
 	}
 
 	w.WriteString(fmt.Sprintf(`<div id="outline-container-%s" class="outline-%d">`, h.ID(), h.Lvl+1) + "\n")

org/testdata/headlines.html

@@ -10,8 +10,6 @@
 </li>
 <li><a href="#headline-5">headline with custom status</a>
 </li>
-<li><a href="#headline-6">excluded headline</a>
-</li>
 <li><a href="#headline-7">malformed property drawer</a>
 </li>
 <li><a href="#headline-8">level limit for headlines to be included in the table of contents</a>