FEATURE: up/down arrow will highlight search result

Then you can use enter to visit result.

app/assets/javascripts/discourse/widgets/search-menu-results.js.es6

@@ -20,13 +20,18 @@ class Highlighted extends RawHtml {
 function createSearchResult({ type, linkField, builder }) {
   return createWidget(`search-result-${type}`, {
     html(attrs) {
-      return attrs.results.map(r => {
 
+      let i=-1;
+
+      return attrs.results.map(r => {
+        i+=1;
         let searchResultId;
         if (type === "topic") {
           searchResultId = r.get('topic_id');
         }
-        return h('li', this.attach('link', {
+        let className = i === attrs.selected ? '.selected' : '';
+
+        return h('li' + className, { attributes: { tabindex: '-1' } }, this.attach('link', {
           href: r.get(linkField),
           contents: () => builder.call(this, r, attrs.term),
           className: 'search-link',
@@ -126,7 +131,8 @@ createWidget('search-menu-results', {
           searchContextEnabled: attrs.searchContextEnabled,
           searchLogId: attrs.results.grouped_search_result.search_log_id,
           results: rt.results,
-          term: attrs.term
+          term: attrs.term,
+          selected: (attrs.selected && attrs.selected.type === rt.type) ? attrs.selected.index : -1
         })),
         h('div.no-results', more)
       ];

app/assets/javascripts/discourse/widgets/search-menu.js.es6

@@ -9,7 +9,8 @@ const searchData = {
   noResults: false,
   term: undefined,
   typeFilter: null,
-  invalidTerm: false
+  invalidTerm: false,
+  selected: null
 };
 
 // Helps with debouncing and cancelling promises
@@ -132,7 +133,8 @@ export default createWidget('search-menu', {
           noResults: searchData.noResults,
           results: searchData.results,
           invalidTerm: searchData.invalidTerm,
-          searchContextEnabled: searchData.contextEnabled
+          searchContextEnabled: searchData.contextEnabled,
+          selected: searchData.selected
         }));
       }
     }
@@ -169,6 +171,81 @@ export default createWidget('search-menu', {
     this.sendWidgetAction('toggleSearchMenu');
   },
 
+  keyDown(e) {
+    if (searchData.loading || searchData.noResults) {
+      return;
+    }
+
+    if (e.which === 13 /*enter*/ && searchData.selected) {
+      searchData.selected = null;
+      $('header .results li.selected a').click();
+    }
+
+    if (e.which === 38 /*arrow up*/ || e.which === 40 /*arrow down*/) {
+      this.moveSelected(e.which === 38 ? -1 : 1);
+
+      this.scheduleRerender();
+
+      Em.run.next(()=>{
+          if (searchData.selected) {
+
+            // so we do not clear selected
+            $('header .results li').off('blur');
+
+            let selected = $('header .results li.selected')
+              .focus()
+              .on('blur', ()=> {
+                searchData.selected = null;
+                this.scheduleRerender();
+                selected.off('blur');
+              });
+
+          } else {
+            $('#search-term').focus();
+          }
+      });
+
+      e.preventDefault();
+      return false;
+    }
+  },
+
+  moveSelected(offset) {
+
+    if (offset === 1 && !searchData.selected) {
+      searchData.selected = {type: searchData.results.resultTypes[0].type, index: 0};
+      return;
+    }
+
+    if (!searchData.selected) {
+      return;
+    }
+
+    let typeIndex = _.findIndex(searchData.results.resultTypes, item => item.type === searchData.selected.type);
+
+    if (typeIndex === 0 && searchData.selected.index === 0 && offset === -1) {
+      searchData.selected = null;
+      return;
+    }
+
+    let currentResults = searchData.results.resultTypes[typeIndex].results;
+    let newPosition = searchData.selected.index + offset;
+
+    if (newPosition < currentResults.length && newPosition >= 0) {
+      searchData.selected.index = newPosition;
+    } else {
+      // possibly move to next type
+      let newTypeIndex = typeIndex + offset;
+      if (newTypeIndex >= 0 && newTypeIndex < searchData.results.resultTypes.length) {
+        newPosition = 0;
+        if (offset === -1) {
+          newPosition = searchData.results.resultTypes[newTypeIndex].results.length - 1;
+        }
+        searchData.selected = {type: searchData.results.resultTypes[newTypeIndex].type, index: newPosition};
+      }
+    }
+  },
+
   triggerSearch() {
     searchData.noResults = false;
     this.searchService().set('highlightTerm', searchData.term);

app/assets/stylesheets/common/base/menu-panel.scss

@@ -148,6 +148,13 @@
     padding: 5px;
     text-align: center;
   }
+
+  li.selected {
+    background-color: $highlight-medium;
+  }
+  li:focus {
+    outline: none;
+  }
   .filter {
     padding: 0;
     &:hover {background: transparent;}