feat: Add getActiveSpan to trace API (#163)

Co-authored-by: Daniel Dyla <dyladan@users.noreply.github.com>

Author: cartermp

src/api/trace.ts

@@ -28,6 +28,7 @@ import { Tracer } from '../trace/tracer';
 import { TracerProvider } from '../trace/tracer_provider';
 import {
   deleteSpan,
+  getActiveSpan,
   getSpan,
   getSpanContext,
   setSpan,
@@ -102,6 +103,8 @@ export class TraceAPI {
 
   public getSpan = getSpan;
 
+  public getActiveSpan = getActiveSpan;
+
   public getSpanContext = getSpanContext;
 
   public setSpan = setSpan;

src/trace/context-utils.ts

@@ -19,6 +19,7 @@ import { Context } from '../context/types';
 import { Span } from './span';
 import { SpanContext } from './span_context';
 import { NonRecordingSpan } from './NonRecordingSpan';
+import { ContextAPI } from '../api/context';
 
 /**
  * span key
@@ -34,6 +35,13 @@ export function getSpan(context: Context): Span | undefined {
   return (context.getValue(SPAN_KEY) as Span) || undefined;
 }
 
+/**
+ * Gets the span from the current context, if one exists.
+ */
+export function getActiveSpan(): Span | undefined {
+  return getSpan(ContextAPI.getInstance().active());
+}
+
 /**
  * Set the span on a context
  *

test/api/api.test.ts

@@ -52,6 +52,17 @@ describe('API', () => {
     assert.strictEqual(typeof tracer, 'object');
   });
 
+  it('getActiveSpan should get the current span', () => {
+    const span = new NonRecordingSpan();
+    const ctx = trace.setSpan(ROOT_CONTEXT, span);
+    context.setGlobalContextManager({ active: () => ctx, disable: () => {} } as any);
+    
+    const active = trace.getActiveSpan();
+    assert.strictEqual(active, span);
+
+    context.disable();
+  });
+
   describe('Context', () => {
     it('with should forward this, arguments and return value', () => {
       function fnWithThis(this: string, a: string, b: number): string {