From 96f29e4f2a437ce8d90ef75d3811b268ad8c76c2 Mon Sep 17 00:00:00 2001
From: Svetlana Brennan <50715937+svetlanabrennan@users.noreply.github.com>
Date: Thu, 30 Jan 2025 15:00:01 -0600
Subject: [PATCH 1/2] wip undefined as default

---
 lib/config/index.js                      |  2 +-
 test/unit/config/config-defaults.test.js | 38 ++++++++++++++++++++++++
 2 files changed, 39 insertions(+), 1 deletion(-)

diff --git a/lib/config/index.js b/lib/config/index.js
index 7ce5befb38..dad6936351 100644
--- a/lib/config/index.js
+++ b/lib/config/index.js
@@ -1042,7 +1042,7 @@ Config.prototype._fromPassed = function _fromPassed(external, internal, arbitrar
 
   Object.keys(external).forEach(function overwrite(key) {
     // if it's not in the defaults, it doesn't exist
-    if (!arbitrary && internal[key] === undefined) {
+    if (!arbitrary && !(key in internal)) {
       return
     }
 
diff --git a/test/unit/config/config-defaults.test.js b/test/unit/config/config-defaults.test.js
index 61e344771a..af282116ce 100644
--- a/test/unit/config/config-defaults.test.js
+++ b/test/unit/config/config-defaults.test.js
@@ -10,6 +10,8 @@ const assert = require('node:assert')
 const path = require('path')
 
 const Config = require('../../../lib/config')
+const proxyquire = require('proxyquire')
+const sinon = require('sinon')
 
 test('with default properties', async (t) => {
   let configuration = null
@@ -316,3 +318,39 @@ test('with default properties', async (t) => {
     assert.equal(configuration.instrumentation.npmlog.enabled, true)
   })
 })
+
+test('with undefined as default', async (t) => {
+  let configuration = null
+
+  const mockConfig = {
+    agent_control: {
+      health: {
+        delivery_location: {
+          default: undefined
+        }
+      }
+    }
+  }
+
+  const Config = proxyquire('../../../lib/config/index', {
+    './default': {
+      defaultConfig: sinon.stub().returns(mockConfig)
+    }
+  })
+
+  configuration = Config.initialize({
+    agent_control: {
+      enabled: true,
+      health: {
+        delivery_location: 'file://find/me',
+        frequency: 10
+      }
+    }
+  })
+
+  assert.strictEqual(configuration.agent_control.health.delivery_location.default, undefined)
+
+  await t.test('should have nest item as find me', () => {
+    assert.equal(configuration.agent_control.health.delivery_location, 'file://find/me')
+  })
+})

From 14672bd9a3efbce1147d9c3abc3a8fd7a622919c Mon Sep 17 00:00:00 2001
From: Svetlana Brennan <50715937+svetlanabrennan@users.noreply.github.com>
Date: Fri, 31 Jan 2025 11:52:26 -0600
Subject: [PATCH 2/2] fix stubbing in test

---
 test/unit/config/config-defaults.test.js | 37 ++++++++++--------------
 1 file changed, 16 insertions(+), 21 deletions(-)

diff --git a/test/unit/config/config-defaults.test.js b/test/unit/config/config-defaults.test.js
index af282116ce..0cd04f627d 100644
--- a/test/unit/config/config-defaults.test.js
+++ b/test/unit/config/config-defaults.test.js
@@ -11,7 +11,6 @@ const path = require('path')
 
 const Config = require('../../../lib/config')
 const proxyquire = require('proxyquire')
-const sinon = require('sinon')
 
 test('with default properties', async (t) => {
   let configuration = null
@@ -320,37 +319,33 @@ test('with default properties', async (t) => {
 })
 
 test('with undefined as default', async (t) => {
-  let configuration = null
-
   const mockConfig = {
-    agent_control: {
-      health: {
-        delivery_location: {
+    fake_key: {
+      another_layer: {
+        fake_nested_key: {
           default: undefined
         }
       }
     }
   }
 
-  const Config = proxyquire('../../../lib/config/index', {
-    './default': {
-      defaultConfig: sinon.stub().returns(mockConfig)
-    }
+  const defaults = require('../../../lib/config/default')
+  const orig = defaults.definition
+  defaults.definition = function stub() {
+    const configDefaults = orig.apply(this, arguments)
+    return { ...configDefaults, ...mockConfig }
+  }
+  const Config = proxyquire('../../../lib/config', {
+    './default': defaults
   })
 
-  configuration = Config.initialize({
-    agent_control: {
-      enabled: true,
-      health: {
-        delivery_location: 'file://find/me',
-        frequency: 10
+  const configuration = Config.initialize({
+    fake_key: {
+      another_layer: {
+        fake_nested_key: 'fake-value'
       }
     }
   })
 
-  assert.strictEqual(configuration.agent_control.health.delivery_location.default, undefined)
-
-  await t.test('should have nest item as find me', () => {
-    assert.equal(configuration.agent_control.health.delivery_location, 'file://find/me')
-  })
+  assert.equal(configuration.fake_key.another_layer.fake_nested_key, 'fake-value')
 })