From 7472f83d0ca83208d2dfe4d874f51638385e4145 Mon Sep 17 00:00:00 2001
From: Sven Slootweg <admin@cryto.net>
Date: Mon, 22 Jun 2020 02:25:19 +0200
Subject: [PATCH] Don't scatter explicit undefineds through objects because of
 unused rules

---
 example.js | 3 ++-
 index.js   | 6 +++++-
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/example.js b/example.js
index 68a8413..5a6abe0 100644
--- a/example.js
+++ b/example.js
@@ -5,7 +5,8 @@ const { validateValue } = require("@validatem/core");
 const isString = require("@validatem/is-string");
 
 let validator = hasShape({
-	foo: [ isString ]
+	foo: [ isString ],
+	unused: [ isString ]
 });
 
 let objectA = {
diff --git a/index.js b/index.js
index 693f80c..e45e75a 100644
--- a/index.js
+++ b/index.js
@@ -75,7 +75,11 @@ module.exports = function hasShape(rules) {
 					});
 
 					errors.push(... annotatedErrors);
-					newObject[key] = newValue;
+
+					// Don't scatter explicit `undefined`s across the result object, just because an optional rule existed for some properties but the corresponding value didn't
+					if (newValue !== undefined) {
+						newObject[key] = newValue;
+					}
 				} else {
 					// Extraneous property
 					newObject[key] = value;