From 36ea38302d0c502a41371e484dc67f2a229f4fa4 Mon Sep 17 00:00:00 2001
From: Valeri Karpov <val@karpov.io>
Date: Mon, 24 Jun 2024 12:40:41 -0400
Subject: [PATCH] fix(projection): handle projections on arrays in
 `Model.hydrate()` projection option

Fix #14680
---
 lib/helpers/projection/applyProjection.js       |  6 ++++++
 test/helpers/projection.applyProjection.test.js | 11 +++++++++++
 2 files changed, 17 insertions(+)

diff --git a/lib/helpers/projection/applyProjection.js b/lib/helpers/projection/applyProjection.js
index 1552e07e686..7a35b128b24 100644
--- a/lib/helpers/projection/applyProjection.js
+++ b/lib/helpers/projection/applyProjection.js
@@ -35,6 +35,9 @@ function applyExclusiveProjection(doc, projection, hasIncludedChildren, projecti
   if (doc == null || typeof doc !== 'object') {
     return doc;
   }
+  if (Array.isArray(doc)) {
+    return doc.map(el => applyExclusiveProjection(el, projection, hasIncludedChildren, projectionLimb, prefix));
+  }
   const ret = { ...doc };
   projectionLimb = prefix ? (projectionLimb || {}) : projection;
 
@@ -57,6 +60,9 @@ function applyInclusiveProjection(doc, projection, hasIncludedChildren, projecti
   if (doc == null || typeof doc !== 'object') {
     return doc;
   }
+  if (Array.isArray(doc)) {
+    return doc.map(el => applyInclusiveProjection(el, projection, hasIncludedChildren, projectionLimb, prefix));
+  }
   const ret = { ...doc };
   projectionLimb = prefix ? (projectionLimb || {}) : projection;
 
diff --git a/test/helpers/projection.applyProjection.test.js b/test/helpers/projection.applyProjection.test.js
index fadfe53fa25..e73d0d657ee 100644
--- a/test/helpers/projection.applyProjection.test.js
+++ b/test/helpers/projection.applyProjection.test.js
@@ -21,4 +21,15 @@ describe('applyProjection', function() {
     assert.deepEqual(applyProjection(obj, { 'nested.str2': 0 }), { str: 'test', nested: { num3: 42 } });
     assert.deepEqual(applyProjection(obj, { nested: { num3: 0 } }), { str: 'test', nested: { str2: 'test2' } });
   });
+
+  it('handles projections underneath arrays (gh-14680)', function() {
+    const obj = {
+      _id: 12,
+      testField: 'foo',
+      testArray: [{ _id: 42, field1: 'bar' }]
+    };
+
+    assert.deepEqual(applyProjection(obj, { 'testArray.field1': 1 }), { testArray: [{ field1: 'bar' }] });
+    assert.deepEqual(applyProjection(obj, { 'testArray.field1': 0, _id: 0 }), { testField: 'foo', testArray: [{ _id: 42 }] });
+  });
 });