add test and extensionEnabled method

Author: amymin00

src/index.spec.ts

@@ -11,6 +11,7 @@ import {
 } from "./index";
 import { incrementErrorsMetric, incrementInvocationsMetric } from "./metrics/enhanced-metrics";
 import { LogLevel, setLogLevel } from "./utils";
+import mock from "mock-fs";
 
 jest.mock("./metrics/enhanced-metrics");
 
@@ -319,6 +320,27 @@ describe("datadog", () => {
     expect(mockedIncrementErrors).toBeCalledTimes(0);
   });
 
+  it("doesn't increment enhanced metrics when using extension", async () => {
+    process.env.DD_ENHANCED_METRICS = "false";
+    mock({
+      "/opt/extensions/datadog-agent": Buffer.from([0]),
+    });
+
+    const handlerError: Handler = (event, context, callback) => {
+      throw Error("Some error");
+    };
+
+    const wrappedHandler = datadog(handlerError, { forceWrap: true });
+
+    const result = wrappedHandler({}, mockContext, () => {});
+    await expect(result).rejects.toEqual(Error("Some error"));
+
+    expect(mockedIncrementInvocations).toBeCalledTimes(0);
+    expect(mockedIncrementErrors).toBeCalledTimes(0);
+
+    mock.restore();
+  });
+
   it("use custom logger to log debug messages", async () => {
     const logger = {
       debug: jest.fn(),

src/index.ts

@@ -1,5 +1,4 @@
 import { Context, Handler } from "aws-lambda";
-import { existsSync } from "fs";
 import { MetricsConfig } from "./metrics";
 import type { MetricsListener as MetricsListenerType } from "./metrics";
 
@@ -14,6 +13,7 @@ import {
   setLogger,
   setLogLevel,
 } from "./utils";
+import { extensionEnabled } from "./utils/extension-enabled";
 
 export { TraceHeaders } from "./trace";
 
@@ -31,7 +31,6 @@ export const lambdaTaskRootEnvVar = "LAMBDA_TASK_ROOT";
 export const mergeXrayTracesEnvVar = "DD_MERGE_XRAY_TRACES";
 export const traceExtractorEnvVar = "DD_TRACE_EXTRACTOR";
 export const defaultSiteURL = "datadoghq.com";
-const EXTENSION_PATH = "/opt/extensions/datadog-agent";
 
 interface GlobalConfig {
   /**
@@ -154,7 +153,6 @@ export function datadog<TEvent, TResult>(
             finalConfig.captureLambdaPayload,
           );
           if (responseIs5xxError && !isExtensionEnabled()) {
-            // TODO [ASTUYVE] - verify this behavior is modeled in extension
             incrementErrorsMetric(metricsListener, context);
           }
         }
@@ -303,6 +301,6 @@ function isExtensionEnabled(): boolean {
   if (isExtension !== undefined) {
     return isExtension;
   }
-  isExtension = existsSync(EXTENSION_PATH);
+  isExtension = extensionEnabled();
   return isExtension;
 }

src/metrics/extension.ts

@@ -1,15 +1,14 @@
 import { URL } from "url";
 import { get, post, logDebug, logError } from "../utils";
-import fs from "fs";
+import { extensionEnabled } from "../utils/extension-enabled";
 
 export const AGENT_URL = "http://127.0.0.1:8124";
 const HELLO_PATH = "/lambda/hello";
 const FLUSH_PATH = "/lambda/flush";
-const EXTENSION_PATH = "/opt/extensions/datadog-agent";
 const AGENT_TIMEOUT_MS = 100;
 
 export async function isAgentRunning() {
-  const extensionExists = await fileExists(EXTENSION_PATH);
+  const extensionExists = extensionEnabled();
   if (!extensionExists) {
     logDebug(`Agent isn't present in sandbox`);
     return false;
@@ -33,10 +32,3 @@ export async function flushExtension(): Promise<boolean> {
   }
   return true;
 }
-
-function fileExists(filename: string): Promise<boolean> {
-  return fs.promises
-    .access(filename, fs.constants.F_OK)
-    .then(() => true)
-    .catch(() => false);
-}

src/utils/extension-enabled.ts

@@ -0,0 +1,7 @@
+import { existsSync } from "fs";
+
+const EXTENSION_PATH = "/opt/extensions/datadog-agent";
+
+export function extensionEnabled() {
+  return existsSync(EXTENSION_PATH);
+}