From 8f2209f8931538de105ed72e4ab7ee6935c98387 Mon Sep 17 00:00:00 2001
From: Jordan Worner <jordan.worner@gmail.com>
Date: Wed, 30 Jun 2021 14:00:55 +0100
Subject: [PATCH] fix(propagator-b3): update extract to check for array (#2285)

* fix(propagator-b3): update extract to check for array

* fix(propagator-b3): normalize header value

Co-authored-by: Daniel Dyla <dyladan@users.noreply.github.com>
---
 .../src/B3Propagator.ts                       |  5 +++-
 .../test/B3Propagator.test.ts                 | 25 +++++++++++++++++++
 2 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/packages/opentelemetry-propagator-b3/src/B3Propagator.ts b/packages/opentelemetry-propagator-b3/src/B3Propagator.ts
index 597873e36d..760752d84b 100644
--- a/packages/opentelemetry-propagator-b3/src/B3Propagator.ts
+++ b/packages/opentelemetry-propagator-b3/src/B3Propagator.ts
@@ -61,7 +61,10 @@ export class B3Propagator implements TextMapPropagator {
   }
 
   extract(context: Context, carrier: unknown, getter: TextMapGetter): Context {
-    if (getter.get(carrier, B3_CONTEXT_HEADER)) {
+    const header = getter.get(carrier, B3_CONTEXT_HEADER);
+    const b3Context = Array.isArray(header) ? header[0] : header;
+
+    if (b3Context) {
       return this._b3SinglePropagator.extract(context, carrier, getter);
     } else {
       return this._b3MultiPropagator.extract(context, carrier, getter);
diff --git a/packages/opentelemetry-propagator-b3/test/B3Propagator.test.ts b/packages/opentelemetry-propagator-b3/test/B3Propagator.test.ts
index 6efec8336a..6e5a7b4a7c 100644
--- a/packages/opentelemetry-propagator-b3/test/B3Propagator.test.ts
+++ b/packages/opentelemetry-propagator-b3/test/B3Propagator.test.ts
@@ -152,6 +152,31 @@ describe('B3Propagator', () => {
       });
     });
 
+    it('extracts multi header b3 using array getter', () => {
+      const context = propagator.extract(
+        ROOT_CONTEXT,
+        b3MultiCarrier,
+        {
+          get(carrier, key) {
+            if (carrier == null || carrier[key] === undefined) {
+              return [];
+            }
+            return [carrier[key]];
+          },
+        
+          keys: defaultTextMapGetter.keys
+        }
+      );
+
+      const extractedSpanContext = trace.getSpanContext(context);
+      assert.deepStrictEqual(extractedSpanContext, {
+        spanId: '6e0c63257de34c92',
+        traceId: 'd4cda95b652f4a1592b449d5929fda1b',
+        isRemote: true,
+        traceFlags: TraceFlags.SAMPLED,
+      });
+    });
+
     it('extracts single header over multi', () => {
       const context = propagator.extract(
         ROOT_CONTEXT,