From da737f1c1eda59d7e340c4026a212d21abcb72d6 Mon Sep 17 00:00:00 2001
From: Thomas Ankcorn <thomasankcorn@gmail.com>
Date: Tue, 2 May 2023 12:59:04 +0100
Subject: [PATCH] fix: .cjs extension support for lambda functions (#1442)

---
 .../src/instrumentation.ts                       | 12 ++++++++++--
 .../test/integrations/lambda-handler.test.ts     | 16 ++++++++++++++++
 .../test/lambda-test/commonjs.cjs                |  3 +++
 3 files changed, 29 insertions(+), 2 deletions(-)
 create mode 100644 plugins/node/opentelemetry-instrumentation-aws-lambda/test/lambda-test/commonjs.cjs

diff --git a/plugins/node/opentelemetry-instrumentation-aws-lambda/src/instrumentation.ts b/plugins/node/opentelemetry-instrumentation-aws-lambda/src/instrumentation.ts
index 04b51a9842d..0110293ef76 100644
--- a/plugins/node/opentelemetry-instrumentation-aws-lambda/src/instrumentation.ts
+++ b/plugins/node/opentelemetry-instrumentation-aws-lambda/src/instrumentation.ts
@@ -15,6 +15,7 @@
  */
 
 import * as path from 'path';
+import * as fs from 'fs';
 
 import {
   InstrumentationBase,
@@ -99,8 +100,15 @@ export class AwsLambdaInstrumentation extends InstrumentationBase {
     // Lambda loads user function using an absolute path.
     let filename = path.resolve(taskRoot, moduleRoot, module);
     if (!filename.endsWith('.js')) {
-      // Patching infrastructure currently requires a filename when requiring with an absolute path.
-      filename += '.js';
+      // its impossible to know in advance if the user has a cjs or js file.
+      // check that the .js file exists otherwise fallback to next known possibility
+      try {
+        fs.statSync(`${filename}.js`);
+        filename += '.js';
+      } catch (e) {
+        // fallback to .cjs
+        filename += '.cjs';
+      }
     }
 
     return [
diff --git a/plugins/node/opentelemetry-instrumentation-aws-lambda/test/integrations/lambda-handler.test.ts b/plugins/node/opentelemetry-instrumentation-aws-lambda/test/integrations/lambda-handler.test.ts
index b84f834c799..681922fbee3 100644
--- a/plugins/node/opentelemetry-instrumentation-aws-lambda/test/integrations/lambda-handler.test.ts
+++ b/plugins/node/opentelemetry-instrumentation-aws-lambda/test/integrations/lambda-handler.test.ts
@@ -861,5 +861,21 @@ describe('lambda handler', () => {
         assert.strictEqual(span.attributes[ERR_ATTR], error!.message);
       });
     });
+
+    describe('.cjs lambda bundle', () => {
+      it('should export a valid span', async () => {
+        initializeHandler('lambda-test/commonjs.handler');
+        const result = await lambdaRequire('lambda-test/commonjs.cjs').handler(
+          'arg',
+          ctx
+        );
+        assert.strictEqual(result, 'ok');
+        const spans = memoryExporter.getFinishedSpans();
+        const [span] = spans;
+        assert.strictEqual(spans.length, 1);
+        assertSpanSuccess(span);
+        assert.strictEqual(span.parentSpanId, undefined);
+      });
+    });
   });
 });
diff --git a/plugins/node/opentelemetry-instrumentation-aws-lambda/test/lambda-test/commonjs.cjs b/plugins/node/opentelemetry-instrumentation-aws-lambda/test/lambda-test/commonjs.cjs
new file mode 100644
index 00000000000..3fc61adccf2
--- /dev/null
+++ b/plugins/node/opentelemetry-instrumentation-aws-lambda/test/lambda-test/commonjs.cjs
@@ -0,0 +1,3 @@
+exports.handler = async function (event, context) {
+	return "ok";
+};
\ No newline at end of file