From 1035ac4de3002038b30b2c8e8e04d6d6fafca71a Mon Sep 17 00:00:00 2001
From: Paul Draper <paulddraper@gmail.com>
Date: Wed, 13 Jan 2021 09:26:13 -0700
Subject: [PATCH] Pass through context in ProxyTracer.startSpan() (#1604)

Co-authored-by: Daniel Dyla <dyladan@users.noreply.github.com>
---
 .../src/trace/ProxyTracer.ts                  |  5 +--
 .../proxy-tracer.test.ts                      | 32 ++++++++++++++++---
 2 files changed, 30 insertions(+), 7 deletions(-)

diff --git a/packages/opentelemetry-api/src/trace/ProxyTracer.ts b/packages/opentelemetry-api/src/trace/ProxyTracer.ts
index c6e22433e7..591610c3ae 100644
--- a/packages/opentelemetry-api/src/trace/ProxyTracer.ts
+++ b/packages/opentelemetry-api/src/trace/ProxyTracer.ts
@@ -14,6 +14,7 @@
  * limitations under the License.
  */
 
+import { Context } from '@opentelemetry/context-base';
 import { Span, SpanOptions, Tracer } from '..';
 import { NOOP_TRACER } from './NoopTracer';
 import { ProxyTracerProvider } from './ProxyTracerProvider';
@@ -31,8 +32,8 @@ export class ProxyTracer implements Tracer {
     public readonly version?: string
   ) {}
 
-  startSpan(name: string, options?: SpanOptions): Span {
-    return this._getTracer().startSpan(name, options);
+  startSpan(name: string, options?: SpanOptions, context?: Context): Span {
+    return this._getTracer().startSpan(name, options, context);
   }
 
   /**
diff --git a/packages/opentelemetry-api/test/proxy-implementations/proxy-tracer.test.ts b/packages/opentelemetry-api/test/proxy-implementations/proxy-tracer.test.ts
index 41db382f3d..9170f3e44a 100644
--- a/packages/opentelemetry-api/test/proxy-implementations/proxy-tracer.test.ts
+++ b/packages/opentelemetry-api/test/proxy-implementations/proxy-tracer.test.ts
@@ -26,15 +26,22 @@ import {
   Tracer,
   Span,
   NoopTracer,
+  ROOT_CONTEXT,
+  SpanOptions,
 } from '../../src';
 
 describe('ProxyTracer', () => {
   let provider: ProxyTracerProvider;
+  const sandbox = sinon.createSandbox();
 
   beforeEach(() => {
     provider = new ProxyTracerProvider();
   });
 
+  afterEach(() => {
+    sandbox.restore();
+  });
+
   describe('when no delegate is set', () => {
     it('should return proxy tracers', () => {
       const tracer = provider.getTracer('test');
@@ -61,7 +68,6 @@ describe('ProxyTracer', () => {
 
   describe('when delegate is set before getTracer', () => {
     let delegate: TracerProvider;
-    const sandbox = sinon.createSandbox();
     let getTracerStub: sinon.SinonStub;
 
     beforeEach(() => {
@@ -72,10 +78,6 @@ describe('ProxyTracer', () => {
       provider.setDelegate(delegate);
     });
 
-    afterEach(() => {
-      sandbox.restore();
-    });
-
     it('should return tracers directly from the delegate', () => {
       const tracer = provider.getTracer('test', 'v0');
 
@@ -114,5 +116,25 @@ describe('ProxyTracer', () => {
 
       assert.strictEqual(span, delegateSpan);
     });
+
+    it('should pass original arguments to DelegateTracer#startSpan', () => {
+      const startSpanStub = sandbox.stub(delegateTracer, 'startSpan');
+
+      const name = 'name1';
+      const options: SpanOptions = {};
+      const ctx = ROOT_CONTEXT.setValue(Symbol('test'), 1);
+      tracer.startSpan(name, options, ctx);
+
+      // Assert the proxy tracer has the full API of the NoopTracer
+      assert.strictEqual(
+        NoopTracer.prototype.startSpan.length,
+        ProxyTracer.prototype.startSpan.length
+      );
+      assert.deepStrictEqual(Object.getOwnPropertyNames(NoopTracer.prototype), [
+        'constructor',
+        'startSpan',
+      ]);
+      sandbox.assert.calledOnceWithExactly(startSpanStub, name, options, ctx);
+    });
   });
 });