When headers is set to null return undefined (#86)

Co-authored-by: Harvinder Ghotra <[email protected]>

Author: Shankar Rao

src/trace/context.spec.ts

@@ -226,6 +226,10 @@ describe("readTraceFromEvent", () => {
     const result = readTraceFromEvent({});
     expect(result).toBeUndefined();
   });
+  it("returns undefined when headers is null", () => {
+    const result = readTraceFromEvent("some-value");
+    expect(result).toBeUndefined();
+  });
   it("returns undefined when event isn't object", () => {
     const result = readTraceFromEvent("some-value");
     expect(result).toBeUndefined();

src/trace/context.ts

@@ -147,7 +147,8 @@ export function readTraceFromEvent(event: any): TraceContext | undefined {
   }
   const headers = event.headers;
 
-  if (typeof headers !== "object") {
+  // e.g. When lambda is invoked synchronously, headers can be set to null by the caller
+  if (!headers || typeof headers !== "object") {
     return;
   }