Fix Metric: LabelValue (#195)

* Fix Metric: LabelValue

* Add package-lock

Author: mayurkale22

package-lock.json

@@ -136,7 +136,10 @@ export interface TimeSeries {
 }
 
 /** The LabelValue type. null value indicates an unset. */
-export type LabelValue = string|null;
+export interface LabelValue {
+  /** The value for the label. */
+  readonly value: string|null;
+}
 
 /** A timestamped measurement. */
 export interface Point {

packages/opencensus-core/src/metrics/export/types.ts

@@ -73,6 +73,8 @@ export class MetricUtils {
    * @param tags
    */
   static tagValuesToLabelValues(tags: Tags): LabelValue[] {
-    return Object.keys(tags).map(key => tags[key] as LabelValue);
+    return Object.keys(tags).map(key => {
+      return {value: tags[key]} as LabelValue;
+    });
   }
 }

packages/opencensus-core/src/stats/metric-utils.ts

@@ -48,6 +48,7 @@ describe('MetricUtil', () => {
   it('should convert tag values to label values', () => {
     const tags: Tags = {test: 'test1', tag: 'test2', empty: '', fake: null};
     assert.deepStrictEqual(
-        MetricUtils.tagValuesToLabelValues(tags), ['test1', 'test2', '', null]);
+        MetricUtils.tagValuesToLabelValues(tags),
+        [{value: 'test1'}, {value: 'test2'}, {value: ''}, {value: null}]);
   });
 });