set CurrentRootSpan when parentSpanId passed on wire (#570)

Author: mayurkale22

packages/opencensus-core/src/trace/model/span.ts

@@ -310,10 +310,8 @@ export class Span implements types.Span {
       parentSpanId: this.parentSpanId,
       traceState: this.traceState
     });
-    if (!this.parentSpanId) {
-      this.tracer.setCurrentRootSpan(this);
-    }
 
+    if (this.isRootSpan()) this.tracer.setCurrentRootSpan(this);
     this.tracer.onStartSpan(this);
   }
 

packages/opencensus-core/test/test-span.ts

@@ -113,6 +113,34 @@ describe('Span', () => {
 
       assert.ok(span.started);
     });
+
+
+    it('should start a RootSpan and set CurrentRootSpan when parentSpanId is empty',
+       () => {
+         const rootSpan = new RootSpan(tracer, name, kind, traceId, '');
+         rootSpan.start();
+         assert.strictEqual(tracer.currentRootSpan, rootSpan);
+
+         const span = new Span(tracer, rootSpan);
+         span.start();
+         assert.strictEqual(tracer.currentRootSpan, rootSpan);
+
+         assert.ok(span.started);
+       });
+
+    it('should start a RootSpan and set CurrentRootSpan when parentSpanId is not empty',
+       () => {
+         const rootSpan =
+             new RootSpan(tracer, name, kind, traceId, 'd5955a12632d46a1');
+         rootSpan.start();
+         assert.strictEqual(tracer.currentRootSpan, rootSpan);
+
+         const span = new Span(tracer, rootSpan);
+         span.start();
+         assert.strictEqual(tracer.currentRootSpan, rootSpan);
+
+         assert.ok(span.started);
+       });
   });
 
   /**