From c0080556c8f8501d39e695a9ccd6308faf9f5287 Mon Sep 17 00:00:00 2001
From: Jacob Page <jpage@godaddy.com>
Date: Wed, 13 Mar 2024 17:25:03 -0700
Subject: [PATCH] Support field customization

Support customization of fields on a per-request basis
---
 packages/ecs-morgan-format/index.d.ts         |  3 +++
 packages/ecs-morgan-format/index.js           |  2 ++
 packages/ecs-morgan-format/test/basic.test.js | 23 +++++++++++++++++++
 3 files changed, 28 insertions(+)

diff --git a/packages/ecs-morgan-format/index.d.ts b/packages/ecs-morgan-format/index.d.ts
index 3ca96a8..33cd253 100644
--- a/packages/ecs-morgan-format/index.d.ts
+++ b/packages/ecs-morgan-format/index.d.ts
@@ -1,3 +1,4 @@
+import type { IncomingMessage, ServerResponse } from 'http';
 import type { FormatFn } from "morgan";
 
 interface Config {
@@ -42,6 +43,8 @@ interface Config {
   /** Specify "event.dataset" field. Defaults `${serviceName}`. */
   eventDataset?: string;
 
+  /** Callback for custom modification of the fields */
+  logHook: (event: { record: any, req: IncomingMessage, res: ServerResponse }) => void;
 }
 
 declare function ecsFormat(config?: Config): FormatFn;
diff --git a/packages/ecs-morgan-format/index.js b/packages/ecs-morgan-format/index.js
index b3d2da7..e4e402a 100644
--- a/packages/ecs-morgan-format/index.js
+++ b/packages/ecs-morgan-format/index.js
@@ -175,6 +175,8 @@ function ecsFormat (opts) {
     formatHttpRequest(ecsFields, req)
     formatHttpResponse(ecsFields, res)
 
+    opts.logHook && opts.logHook({ record: ecsFields, req, res })
+
     return stringify(ecsFields)
   }
 }
diff --git a/packages/ecs-morgan-format/test/basic.test.js b/packages/ecs-morgan-format/test/basic.test.js
index 090986e..dc1c1f3 100644
--- a/packages/ecs-morgan-format/test/basic.test.js
+++ b/packages/ecs-morgan-format/test/basic.test.js
@@ -235,3 +235,26 @@ test('can configure correlation fields', t => {
     t.end()
   })
 })
+
+test('can provide custom fields', t => {
+  t.plan(2)
+
+  const stream = split().on('data', line => {
+    const rec = JSON.parse(line)
+    t.equal(rec.labels.custom, 'customValue')
+  })
+  const logger = morgan(
+    ecsFormat({
+      logHook ({ record, req, res }) {
+        record.labels = record.labels || {}
+        record.labels.custom = 'customValue'
+      }
+    }),
+    { stream }
+  )
+
+  makeExpressServerAndRequest(logger, '/', {}, null, function (err) {
+    t.error(err)
+    t.end()
+  })
+})