From 35224c7e3442f8f965bd543f2d1c8a8c70b47351 Mon Sep 17 00:00:00 2001
From: Naseem <naseem@transit.app>
Date: Tue, 1 Jun 2021 16:36:51 -0400
Subject: [PATCH] =?UTF-8?q?chore:=20function=20overloads=20implementation?=
 =?UTF-8?q?=20of=20startActiveSpan=20in=20noop=20t=E2=80=A6=20(#81)?=
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Co-authored-by: Daniel Dyla <dyladan@users.noreply.github.com>
Co-authored-by: Valentin Marchaud <contact@vmarchaud.fr>
---
 src/trace/NoopTracer.ts                       | 62 ++++++++++---------
 test/noop-implementations/noop-tracer.test.ts | 14 ++---
 2 files changed, 41 insertions(+), 35 deletions(-)

diff --git a/src/trace/NoopTracer.ts b/src/trace/NoopTracer.ts
index b44dde20..238553e6 100644
--- a/src/trace/NoopTracer.ts
+++ b/src/trace/NoopTracer.ts
@@ -49,41 +49,47 @@ export class NoopTracer implements Tracer {
 
   startActiveSpan<F extends (span: Span) => ReturnType<F>>(
     name: string,
-    arg2: F | SpanOptions,
+    fn: F
+  ): ReturnType<F>;
+  startActiveSpan<F extends (span: Span) => ReturnType<F>>(
+    name: string,
+    opts: SpanOptions | undefined,
+    fn: F
+  ): ReturnType<F>;
+  startActiveSpan<F extends (span: Span) => ReturnType<F>>(
+    name: string,
+    opts: SpanOptions | undefined,
+    ctx: Context | undefined,
+    fn: F
+  ): ReturnType<F>;
+  startActiveSpan<F extends (span: Span) => ReturnType<F>>(
+    name: string,
+    arg2?: F | SpanOptions,
     arg3?: F | Context,
     arg4?: F
   ): ReturnType<F> | undefined {
-    let fn: F | undefined,
-      options: SpanOptions | undefined,
-      activeContext: Context | undefined;
-    if (arguments.length === 2 && typeof arg2 === 'function') {
-      fn = arg2;
-    } else if (
-      arguments.length === 3 &&
-      typeof arg2 === 'object' &&
-      typeof arg3 === 'function'
-    ) {
-      options = arg2;
-      fn = arg3;
-    } else if (
-      arguments.length === 4 &&
-      typeof arg2 === 'object' &&
-      typeof arg3 === 'object' &&
-      typeof arg4 === 'function'
-    ) {
-      options = arg2;
-      activeContext = arg3;
-      fn = arg4;
+    let opts: SpanOptions | undefined;
+    let ctx: Context | undefined;
+    let fn: F;
+
+    if (arguments.length < 2) {
+      return;
+    } else if (arguments.length === 2) {
+      fn = arg2 as F;
+    } else if (arguments.length === 3) {
+      opts = arg2 as SpanOptions | undefined;
+      fn = arg3 as F;
+    } else {
+      opts = arg2 as SpanOptions | undefined;
+      ctx = arg3 as Context | undefined;
+      fn = arg4 as F;
     }
 
-    const parentContext = activeContext ?? context.active();
-    const span = this.startSpan(name, options, parentContext);
+    const parentContext = ctx ?? context.active();
+    const span = this.startSpan(name, opts, parentContext);
     const contextWithSpanSet = setSpan(parentContext, span);
 
-    if (fn) {
-      return context.with(contextWithSpanSet, fn, undefined, span);
-    }
-    return;
+    return context.with(contextWithSpanSet, fn, undefined, span);
   }
 }
 
diff --git a/test/noop-implementations/noop-tracer.test.ts b/test/noop-implementations/noop-tracer.test.ts
index 7f23ff22..03701720 100644
--- a/test/noop-implementations/noop-tracer.test.ts
+++ b/test/noop-implementations/noop-tracer.test.ts
@@ -69,16 +69,16 @@ describe('NoopTracer', () => {
       }
     };
     const opts = { attributes: { foo: 'bar' } };
-    const ctx = context.active();
 
-    const a = tracer.startActiveSpan(name, fn);
-    assert.strictEqual(a, 1);
+    assert.strictEqual((tracer as any).startActiveSpan(name), undefined);
 
-    const b = tracer.startActiveSpan(name, opts, fn);
+    assert.strictEqual(tracer.startActiveSpan(name, fn), 1);
 
-    assert.strictEqual(b, 1);
+    assert.strictEqual(tracer.startActiveSpan(name, opts, fn), 1);
 
-    const c = tracer.startActiveSpan(name, opts, ctx, fn);
-    assert.strictEqual(c, 1);
+    assert.strictEqual(
+      tracer.startActiveSpan(name, opts, context.active(), fn),
+      1
+    );
   });
 });