fix(opentelemetry): correct Span.addEvent 2-arg overload

.changeset/fix-span-addevent-overload.md

@@ -0,0 +1,7 @@
+---
+"@effect/opentelemetry": patch
+---
+
+Fix `Span.addEvent` to correctly handle the 2-argument overload with attributes.
+
+Previously, calling `span.addEvent("name", { foo: "bar" })` would throw `TypeError: {} is not iterable` because the implementation incorrectly treated the attributes object as a `TimeInput`. The fix adds proper runtime type discrimination to distinguish between `TimeInput` (number, Date, or HrTime tuple) and `Attributes` (plain object).

packages/opentelemetry/src/internal/tracer.ts

@@ -266,8 +266,13 @@ const makeOtelSpan = (span: EffectTracer.Span, clock: Clock.Clock): OtelApi.Span
       if (arguments.length === 3) {
         attributes = arguments[1]
         startTime = arguments[2]
-      } else {
-        startTime = arguments[1]
+      } else if (arguments.length === 2) {
+        const arg1 = arguments[1]
+        if (isTimeInput(arg1)) {
+          startTime = arg1
+        } else {
+          attributes = arg1
+        }
       }
       span.event(name, convertOtelTimeInput(startTime, clock), attributes)
       return self
@@ -318,6 +323,12 @@ const makeOtelSpan = (span: EffectTracer.Span, clock: Clock.Clock): OtelApi.Span
 const bigint1e6 = BigInt(1_000_000)
 const bigint1e9 = BigInt(1_000_000_000)
 
+/** Distinguishes TimeInput (number | Date | [number, number]) from Attributes (plain object) */
+const isTimeInput = (u: unknown): u is OtelApi.TimeInput =>
+  typeof u === "number" ||
+  u instanceof Date ||
+  (Array.isArray(u) && u.length === 2 && typeof u[0] === "number" && typeof u[1] === "number")
+
 const convertOtelTimeInput = (input: OtelApi.TimeInput | undefined, clock: Clock.Clock): bigint => {
   if (input === undefined) {
     return clock.unsafeCurrentTimeNanos()

packages/opentelemetry/test/Tracer.test.ts

@@ -159,5 +159,71 @@ describe("Tracer", () => {
         ),
         OtlpTracingLive
       ))
+
+    it.effect("addEvent with attributes (2-arg overload) does not throw", () =>
+      Effect.provide(
+        Effect.withSpan("root")(
+          Effect.gen(function*() {
+            const otelSpan = yield* Tracer.currentOtelSpan
+            expect(() => otelSpan.addEvent("test-event", { foo: "bar", count: 42 })).not.toThrow()
+          })
+        ),
+        OtlpTracingLive
+      ))
+
+    it.effect("addEvent with HrTime tuple (2-arg overload) does not throw", () =>
+      Effect.provide(
+        Effect.withSpan("root")(
+          Effect.gen(function*() {
+            const otelSpan = yield* Tracer.currentOtelSpan
+            expect(() => otelSpan.addEvent("test-event", [1, 2])).not.toThrow()
+          })
+        ),
+        OtlpTracingLive
+      ))
+
+    it.effect("addEvent with number timestamp (2-arg overload) does not throw", () =>
+      Effect.provide(
+        Effect.withSpan("root")(
+          Effect.gen(function*() {
+            const otelSpan = yield* Tracer.currentOtelSpan
+            expect(() => otelSpan.addEvent("test-event", Date.now())).not.toThrow()
+          })
+        ),
+        OtlpTracingLive
+      ))
+
+    it.effect("addEvent with Date timestamp (2-arg overload) does not throw", () =>
+      Effect.provide(
+        Effect.withSpan("root")(
+          Effect.gen(function*() {
+            const otelSpan = yield* Tracer.currentOtelSpan
+            expect(() => otelSpan.addEvent("test-event", new Date())).not.toThrow()
+          })
+        ),
+        OtlpTracingLive
+      ))
+
+    it.effect("addEvent with name only (1-arg) does not throw", () =>
+      Effect.provide(
+        Effect.withSpan("root")(
+          Effect.gen(function*() {
+            const otelSpan = yield* Tracer.currentOtelSpan
+            expect(() => otelSpan.addEvent("test-event")).not.toThrow()
+          })
+        ),
+        OtlpTracingLive
+      ))
+
+    it.effect("addEvent with attributes and timestamp (3-arg overload) does not throw", () =>
+      Effect.provide(
+        Effect.withSpan("root")(
+          Effect.gen(function*() {
+            const otelSpan = yield* Tracer.currentOtelSpan
+            expect(() => otelSpan.addEvent("test-event", { foo: "bar" }, Date.now())).not.toThrow()
+          })
+        ),
+        OtlpTracingLive
+      ))
   })
 })