Fix CoreTracerBase not respecting propagated trace options (#811)

Author: philicious

packages/opencensus-core/src/trace/model/tracer-base.ts

@@ -262,11 +262,15 @@ export class CoreTracerBase implements types.TracerBase {
     }
     let propagatedSample = null;
     // if there is a context propagation, keep the decision
-    if (options && options.spanContext && options.spanContext.options) {
+    if (
+      options &&
+      options.spanContext &&
+      options.spanContext.options !== undefined
+    ) {
       propagatedSample = (options.spanContext.options & this.IS_SAMPLED) !== 0;
+      return !!propagatedSample;
     }
-
-    // Propagated sample or use the default global sampler
-    return !!propagatedSample || this.sampler.shouldSample(traceId);
+    // default global sampler
+    return this.sampler.shouldSample(traceId);
   }
 }

packages/opencensus-core/test/test-tracer-base.ts

@@ -225,12 +225,13 @@ describe('Tracer Base', () => {
       });
     });
 
-    it('should create the new RootSpan with no propagation (options bit is not set)', () => {
+    it('should create the new NoRecordRootSpan with propagation options bit set to not-sample)', () => {
       const tracer = new CoreTracerBase();
       tracer.start(defaultConfig);
       traceOptions.spanContext!.options = 0x0;
       tracer.startRootSpan(traceOptions, rootSpan => {
         assert.ok(rootSpan);
+        assert.ok(rootSpan instanceof NoRecordRootSpan);
         assert.strictEqual(rootSpan.name, traceOptions.name);
         assert.strictEqual(rootSpan.kind, traceOptions.kind);
         assert.strictEqual(rootSpan.traceId, spanContextPropagated.traceId);