From b9321b200a6d5ceb5941f1b25e8a290028353fbf Mon Sep 17 00:00:00 2001
From: Adrien Becchis <adrien.becchis@gmail.com>
Date: Sat, 4 Nov 2017 04:22:13 +0100
Subject: [PATCH] transformer can now return an undefined key (#289)

---
 lib/nconf/common.js   |  2 +-
 test/complete-test.js | 28 ++++++++++++++++++++++++++++
 2 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/lib/nconf/common.js b/lib/nconf/common.js
index 9aa69ee..0adcf01 100644
--- a/lib/nconf/common.js
+++ b/lib/nconf/common.js
@@ -154,7 +154,7 @@ common.transform = function(map, fn) {
 
     if (!result) {
       return null;
-    } else if (result.key && typeof result.value !== 'undefined') {
+    } else if (result.key) {
       return result;
     }
 
diff --git a/test/complete-test.js b/test/complete-test.js
index 0245fdf..d1f9462 100644
--- a/test/complete-test.js
+++ b/test/complete-test.js
@@ -242,6 +242,34 @@ vows.describe('nconf/multiple-stores').addBatch({
   teardown: function () {
     nconf.remove('env');
   }
+}).addBatch({
+  // Threw this in it's own batch to make sure it's run separately from the
+  // sync check
+  "When using env with a transform:fn that return an undefined value": {
+    topic: function () {
+
+      function testTransform(obj) {
+        if (obj.key === 'FOO') {
+          return {key: 'FOO', value: undefined};
+        }
+
+        return obj;
+      }
+
+      var that = this;
+      helpers.cp(complete, completeTest, function () {
+        nconf.env({ transform: testTransform });
+        that.callback();
+      });
+    }, "env vars": {
+      "port key/value properly transformed": function() {
+        assert.equal(typeof nconf.get('FOO'), 'undefined');
+      }
+    }
+  },
+  teardown: function () {
+    nconf.remove('env');
+  }
 }).addBatch({
   // Threw this in it's own batch to make sure it's run separately from the
   // sync check