From 25f74bf997a65e18683433b7eeb43ba5c44f60a1 Mon Sep 17 00:00:00 2001
From: Chris Chapman <chris@blackcompanystudios.co.uk>
Date: Wed, 18 Mar 2020 10:29:34 +0000
Subject: [PATCH] Add support for 'add' operation without position. Spec
 (https://tools.ietf.org/html/rfc6902#section-4.1) requires this operation to
 replace an existing target field or add a new one, both of which are covered
 by the same $set mongodb operation.

---
 index.js           |  7 ++++---
 test/index.test.js | 26 ++++++++++++++++----------
 2 files changed, 20 insertions(+), 13 deletions(-)

diff --git a/index.js b/index.js
index 8c7027c..9767577 100644
--- a/index.js
+++ b/index.js
@@ -15,9 +15,8 @@ module.exports = function(patches){
       var key = parts.slice(0, -1).join('.');
       var $position = positionPart && parseInt(positionPart, 10) || null;
 
-      update.$push = update.$push || {};
-
       if ($position !== null) {
+        update.$push = update.$push || {};
         if (update.$push[key] === undefined) {
           update.$push[key] = {
             $each: [p.value],
@@ -35,6 +34,7 @@ module.exports = function(patches){
           update.$push[key].$position = Math.min($position, update.$push[key].$position);
         }
       } else if(addToEnd) {
+        update.$push = update.$push || {};
         if (update.$push[key] === undefined) {
           update.$push[key] = p.value;
         } else {
@@ -49,7 +49,8 @@ module.exports = function(patches){
           update.$push[key].$each.push(p.value);
         }
       } else {
-        throw new Error("Unsupported Operation! can't use add op without position");
+        update.$set = update.$set || {};
+        update.$set[toDot(p.path)] = p.value;
       }
       break;
     case 'remove':
diff --git a/test/index.test.js b/test/index.test.js
index f868581..9b8f99e 100644
--- a/test/index.test.js
+++ b/test/index.test.js
@@ -20,6 +20,22 @@ describe('jsonpatch to mongodb', function() {
     assert.deepEqual(toMongodb(patches), expected);
   });
 
+  it('should allow add to insert or replace a non-array field', function() {
+    var patches = [{
+      op: 'add',
+      path: '/name/nested',
+      value: 'dave'
+    }];
+
+    var expected = {
+      $set: {
+        'name.nested': 'dave'
+      }
+    };
+
+    assert.deepEqual(toMongodb(patches), expected);
+  });
+
   it('should work with escaped characters', function() {
     var patches = [{
       op: 'replace',
@@ -270,16 +286,6 @@ describe('jsonpatch to mongodb', function() {
     chai.expect(function(){toMongodb(patches)}).to.throw("Unsupported Operation! can't use add op with mixed positions");
   });
 
-  it('should blow up on add without position', function() {
-    var patches = [{
-      op: 'add',
-      path: '/name',
-      value: 'dave'
-    }];
-
-    chai.expect(function(){toMongodb(patches)}).to.throw("Unsupported Operation! can't use add op without position");
-  });
-
   it('should blow up on move', function() {
     var patches = [{
       op: 'move',