feat(core-shared/instrumentation): withSpan attaches runtime __instrumented marker

packages/core-shared/src/instrumentation/with-span.test.ts

@@ -2,6 +2,7 @@ import { describe, it, expect, expectTypeOf, vi } from "vitest";
 import { withSpan } from "@/instrumentation/with-span";
 import type { ITracer, ISpan, SpanOpts } from "@/instrumentation/tracer.interface";
 import type { Instrumented } from "@/conformance/brands";
+import { isInstrumented } from "@/conformance/brand-runtime";
 
 function makeRecordingTracer() {
   const calls: SpanOpts[] = [];
@@ -70,3 +71,13 @@ describe("withSpan — brand", () => {
     expectTypeOf(wrapped).toMatchTypeOf<Instrumented<typeof fn>>();
   });
 });
+
+describe("withSpan — runtime brand", () => {
+  it("attaches __instrumented as a non-enumerable property on the wrapped function", async () => {
+    const { tracer } = makeRecordingTracer();
+    const fn = async (a: number) => a + 1;
+    const wrapped = withSpan(tracer, { name: "test.brand", op: "use-case" }, fn);
+    expect(isInstrumented(wrapped)).toBe(true);
+    expect(Object.keys(wrapped)).not.toContain("__instrumented");
+  });
+});