Show valueless labels correctly

For labels that don't have scores (aka values), use `approved` and
`rejected` fields from LabelInfo.

Also, fix runtime exception when valueless label is encountered.

Bug: Issue 8010
Change-Id: I7ed198778012ae94a8b1b165f22c286ba19a7d89

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

@@ -134,10 +134,21 @@
     _computeLabelValues(labelName, _labels) {
       const result = [];
       const labels = _labels.base;
-      const t = labels[labelName];
-      if (!t) { return result; }
-      const approvals = t.all || [];
-      const values = Object.keys(t.values);
+      const labelInfo = labels[labelName];
+      if (!labelInfo) { return result; }
+      if (!labelInfo.values) {
+        if (labelInfo.rejected || labelInfo.approved) {
+          const ok = labelInfo.approved || !labelInfo.rejected;
+          return [{
+            value: ok ? '👍️' : '👎️',
+            className: ok ? 'positive' : 'negative',
+            account: ok ? labelInfo.approved : labelInfo.rejected,
+          }];
+        }
+        return result;
+      }
+      const approvals = labelInfo.all || [];
+      const values = Object.keys(labelInfo.values);
       for (const label of approvals) {
         if (label.value && label.value != labels[labelName].default_value) {
           let labelClassName;

polygerrit-ui/app/elements/change/gr-change-metadata/gr-change-metadata_test.html

@@ -664,6 +664,32 @@ limitations under the License.
     });
 
     suite('label colors', () => {
+      test('valueless label rejected', () => {
+        element.change = {
+          labels: {
+            'Do-Not-Submit': {
+              rejected: {name: 'someone'},
+            },
+          },
+        };
+        flushAsynchronousOperations();
+        const labels = Polymer.dom(element.root).querySelectorAll('gr-label');
+        assert.isTrue(labels[0].classList.contains('negative'));
+      });
+
+      test('valueless label approved', () => {
+        element.change = {
+          labels: {
+            'To-The-Infinity': {
+              approved: {name: 'someone'},
+            },
+          },
+        };
+        flushAsynchronousOperations();
+        const labels = Polymer.dom(element.root).querySelectorAll('gr-label');
+        assert.isTrue(labels[0].classList.contains('positive'));
+      });
+
       test('-2 to +2', () => {
         element.change = {
           labels: {

polygerrit-ui/app/elements/change/gr-label-score-row/gr-label-score-row.js

@@ -142,7 +142,9 @@
     },
 
     _computeLabelValueTitle(labels, label, value) {
-      return labels[label] && labels[label].values[value];
+      return labels[label] &&
+        labels[label].values &&
+        labels[label].values[value];
     },
   });
 })();