fix(pat autotoc): Fix fieldset ID and refactor TOC navigation.

Author: petschki

src/pat/autotoc/autotoc.js

@@ -78,16 +78,21 @@ export default Base.extend({
         var activeId = null;
 
         $(self.options.levels, self.$el).each(function (i) {
-            const section = this.closest(self.options.section);
             const $level = $(this);
-            let id = $level.prop("id") ? $level.prop("id") : $(section).prop("id");
+            const $section = $level.closest(self.options.section);
+            let id = $section.prop("id") || $level.prop("id");
 
-            if (!id || $("#" + id).length > 0) {
+            if (!asTabs || !id || $(`#${id}`).length > 1) {
                 id = self.options.IDPrefix + self.name + "-" + i;
             }
 
             const tabId = `${id}-tab`;
-            $(section).attr("id", id).attr("aria-labelledby", tabId);
+
+            if (!asTabs) {
+                $level.attr("id", id).attr("aria-labelledby", tabId);
+            } else {
+                $section.attr("id", id).attr("aria-labelledby", tabId);
+            }
 
             if (window.location.hash === "#" + id) {
                 activeId = tabId;
@@ -156,25 +161,15 @@ export default Base.extend({
             $level.data("autotoc-trigger-id", id);
 
             self.tabs.push({
-                section: section,
+                section: $section[0],
                 id: id,
                 nav: $nav[0],
             });
         });
 
-        if (activeId) {
-            const activeTabButton = self.$toc.find("a#" + activeId)[0];
-            if (activeTabButton) {
-                const tab = Tab.getOrCreateInstance(activeTabButton);
-                tab.show();
-            }
-        } else {
-            const firstTabButton = self.$toc.find("a").first()[0];
-            if (firstTabButton) {
-                const tab = Tab.getOrCreateInstance(firstTabButton);
-                tab.show();
-            }
-        }
+        const activeTabButton = activeId ? self.$toc.find("a#" + activeId)[0] : self.$toc.find("a").first()[0];
+        const tab = Tab.getOrCreateInstance(activeTabButton);
+        tab.show();
 
         // After DOM tree is built, initialize eventual validation
         this.initialize_validation();