From dc9f4a0d84b9082605930a2bae2acb197a210bff Mon Sep 17 00:00:00 2001
From: Ivan Tanev <vankata.t@gmail.com>
Date: Wed, 24 Jun 2020 14:59:55 +0300
Subject: [PATCH 1/2] Handle sparse array positions as undefined

---
 src/array.js  | 14 ++++++++------
 test/array.js | 16 ++++++++++++++++
 2 files changed, 24 insertions(+), 6 deletions(-)

diff --git a/src/array.js b/src/array.js
index 76c536be4..d06f2312c 100644
--- a/src/array.js
+++ b/src/array.js
@@ -84,8 +84,10 @@ inherits(ArraySchema, MixedSchema, {
 
         originalValue = originalValue || value;
 
-        let validations = value.map((item, idx) => {
-          var path = makePath`${options.path}[${idx}]`;
+        let validations = new Array(value.length);
+        for (let idx = 0; idx < value.length; idx++) {
+          let item = value[idx];
+          let path = makePath`${options.path}[${idx}]`;
 
           // object._validate note for isStrict explanation
           var innerOptions = {
@@ -97,10 +99,10 @@ inherits(ArraySchema, MixedSchema, {
             originalValue: originalValue[idx],
           };
 
-          if (innerType.validate) return innerType.validate(item, innerOptions);
-
-          return true;
-        });
+          validations[idx] = innerType.validate
+            ? innerType.validate(item, innerOptions)
+            : true;
+        }
 
         return runValidations({
           sync,
diff --git a/test/array.js b/test/array.js
index a09081702..b5b5a8576 100644
--- a/test/array.js
+++ b/test/array.js
@@ -202,4 +202,20 @@ describe('Array types', () => {
       .of(itemSchema)
       .validate(value);
   });
+
+  it('should maintain array sparseness through validation', async () => {
+    let sparseArray = new Array(2);
+    sparseArray[1] = 1;
+    let value = await array().of(number()).validate(sparseArray);
+    expect(0 in sparseArray).to.be.false()
+    expect(0 in value).to.be.false()
+    // eslint-disable-next-line no-sparse-arrays
+    value.should.eql([,1]);
+  });
+
+  it('should validate empty slots in sparse array', async () => {
+    let sparseArray = new Array(2);
+    sparseArray[1] = 1;
+    await array().of(number().required()).isValid(sparseArray).should.become(false);
+  });
 });

From 6d12d2c11c0b40b040f2930b693f257204bff2b2 Mon Sep 17 00:00:00 2001
From: Jason Quense <monastic.panic@gmail.com>
Date: Thu, 25 Jun 2020 10:35:40 -0400
Subject: [PATCH 2/2] Update src/array.js

---
 src/array.js | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/array.js b/src/array.js
index d06f2312c..3313c0cd0 100644
--- a/src/array.js
+++ b/src/array.js
@@ -84,6 +84,7 @@ inherits(ArraySchema, MixedSchema, {
 
         originalValue = originalValue || value;
 
+        // #950 Ensure that sparse array empty slots are validated
         let validations = new Array(value.length);
         for (let idx = 0; idx < value.length; idx++) {
           let item = value[idx];