Fix moving cursor across sections in dashboard

Change I7baad12a02e0e9e53b74537215ddbf21c7b2d006 introduced a regression
where the cursor indicator disappears when moved below the first section
containing results. This change fixes the root cause, refactors
slightly, and adds tests.

Bug: Issue 7118
Change-Id: Ide4f31af2af161dc1085167740b698c5507953ac

polygerrit-ui/app/elements/change-list/gr-change-list/gr-change-list.html

@@ -94,7 +94,7 @@ limitations under the License.
         </template>
         <template is="dom-repeat" items="[[changeSection.results]]" as="change">
           <gr-change-list-item
-              selected$="[[_computeItemSelected(index, sectionIndex, selectedIndex)]]"
+              selected$="[[_computeItemSelected(sectionIndex, index, selectedIndex)]]"
               assigned$="[[_computeItemAssigned(account, change)]]"
               needs-review$="[[_computeItemNeedsReview(account, change, showReviewedState)]]"
               change="[[change]]"

polygerrit-ui/app/elements/change-list/gr-change-list/gr-change-list.js

@@ -179,12 +179,24 @@
       return `${this.getBaseUrl()}/q/${this.encodeURL(query, true)}`;
     },
 
-    _computeItemSelected(index, sectionIndex, selectedIndex) {
+    /**
+     * Maps an index local to a particular section to the absolute index
+     * across all the changes on the page.
+     *
+     * @param sectionIndex {number} index of section
+     * @param localIndex {number} index of row within section
+     * @return {number} absolute index of row in the aggregate dashboard
+     */
+    _computeItemAbsoluteIndex(sectionIndex, localIndex) {
       let idx = 0;
       for (let i = 0; i < sectionIndex; i++) {
-        idx += this.sections[i].length;
+        idx += this.sections[i].results.length;
       }
-      idx += index;
+      return idx + localIndex;
+    },
+
+    _computeItemSelected(sectionIndex, index, selectedIndex) {
+      const idx = this._computeItemAbsoluteIndex(sectionIndex, index);
       return idx == selectedIndex;
     },
 
@@ -199,21 +211,13 @@
       return account._account_id === change.assignee._account_id;
     },
 
-    _getAggregatesectionsLen(sections) {
-      sections = sections || [];
-      let len = 0;
-      for (const section of this.sections) {
-        len += section.length;
-      }
-      return len;
-    },
-
     _handleJKey(e) {
       if (this.shouldSuppressKeyboardShortcut(e) ||
           this.modifierPressed(e)) { return; }
 
       e.preventDefault();
-      const len = this._getAggregatesectionsLen(this.sections);
+      // Compute absolute index of item that would come after final item.
+      const len = this._computeItemAbsoluteIndex(this.sections.length, 0);
       if (this.selectedIndex === len - 1) { return; }
       this.selectedIndex += 1;
     },

polygerrit-ui/app/elements/change-list/gr-change-list/gr-change-list_test.html

@@ -148,6 +148,11 @@ limitations under the License.
     });
 
     test('keyboard shortcuts', done => {
+      sandbox.stub(element, '_computeLabelNames');
+      element.sections = [
+        {results: new Array(1)},
+        {results: new Array(2)},
+      ];
       element.selectedIndex = 0;
       element.changes = [
         {_number: 0},
@@ -163,7 +168,10 @@ limitations under the License.
         assert.isTrue(elementItems[0].hasAttribute('selected'));
         MockInteractions.pressAndReleaseKeyOn(element, 74, null, 'j');
         assert.equal(element.selectedIndex, 1);
+        assert.isTrue(elementItems[1].hasAttribute('selected'));
         MockInteractions.pressAndReleaseKeyOn(element, 74, null, 'j');
+        assert.equal(element.selectedIndex, 2);
+        assert.isTrue(elementItems[2].hasAttribute('selected'));
 
         const navStub = sandbox.stub(Gerrit.Nav, 'navigateToChange');
         assert.equal(element.selectedIndex, 2);
@@ -484,5 +492,24 @@ limitations under the License.
               'is:open ((reviewer:self -is:ignored) OR assignee:self)'),
           '/q/is:open+((reviewer:self+-is:ignored)+OR+assignee:self)');
     });
+
+    test('_computeItemAbsoluteIndex', () => {
+      sandbox.stub(element, '_computeLabelNames');
+      element.sections = [
+        {results: new Array(1)},
+        {results: new Array(2)},
+        {results: new Array(3)},
+      ];
+
+      assert.equal(element._computeItemAbsoluteIndex(0, 0), 0);
+      // Out of range but no matter.
+      assert.equal(element._computeItemAbsoluteIndex(0, 1), 1);
+
+      assert.equal(element._computeItemAbsoluteIndex(1, 0), 1);
+      assert.equal(element._computeItemAbsoluteIndex(1, 1), 2);
+      assert.equal(element._computeItemAbsoluteIndex(1, 2), 3);
+      assert.equal(element._computeItemAbsoluteIndex(2, 0), 3);
+      assert.equal(element._computeItemAbsoluteIndex(3, 0), 6);
+    });
   });
 </script>