From a37480eec9664989fdb62aed54a66006110ce6bd Mon Sep 17 00:00:00 2001
From: Benoit Blanchon <git@benoitblanchon.fr>
Date: Fri, 27 Sep 2019 10:01:17 +0200
Subject: [PATCH] Fixed deserializeJson() when input contains duplicate keys
 (fixes #1095)

---
 CHANGELOG.md                              |  1 +
 extras/tests/JsonDeserializer/object.cpp  |  1 +
 src/ArduinoJson/Json/JsonDeserializer.hpp | 18 ++++++++++++------
 3 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index e0178893..5def537c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,7 @@ HEAD
 
 * Added support for custom writer classes (issue #1088)
 * Added conversion from `JsonArray` and `JsonObject` to `bool`, to be consistent with `JsonVariant`
+* Fixed `deserializeJson()` when input contains duplicate keys (issue #1095)
 
 v6.12.0 (2019-09-05)
 -------
diff --git a/extras/tests/JsonDeserializer/object.cpp b/extras/tests/JsonDeserializer/object.cpp
index 739f6d6d..f07c550c 100644
--- a/extras/tests/JsonDeserializer/object.cpp
+++ b/extras/tests/JsonDeserializer/object.cpp
@@ -277,6 +277,7 @@ TEST_CASE("deserialize JSON object") {
       DeserializationError err = deserializeJson(doc, "{a:{b:{c:1}},a:2}");
 
       REQUIRE(err == DeserializationError::Ok);
+      REQUIRE(doc["a"] == 2);
     }
   }
 
diff --git a/src/ArduinoJson/Json/JsonDeserializer.hpp b/src/ArduinoJson/Json/JsonDeserializer.hpp
index 63bc860b..3f08d0bf 100644
--- a/src/ArduinoJson/Json/JsonDeserializer.hpp
+++ b/src/ArduinoJson/Json/JsonDeserializer.hpp
@@ -130,15 +130,21 @@ class JsonDeserializer {
 
     // Read each key value pair
     for (;;) {
-      // Allocate slot in object
-      VariantSlot *slot = object.addSlot(_pool);
-      if (!slot) return DeserializationError::NoMemory;
-
       // Parse key
       const char *key;
       err = parseKey(key);
       if (err) return err;
-      slot->setOwnedKey(make_not_null(key));
+
+      VariantData *variant = object.get(adaptString(key));
+      if (!variant) {
+        // Allocate slot in object
+        VariantSlot *slot = object.addSlot(_pool);
+        if (!slot) return DeserializationError::NoMemory;
+
+        slot->setOwnedKey(make_not_null(key));
+
+        variant = slot->data();
+      }
 
       // Skip spaces
       err = skipSpacesAndComments();
@@ -147,7 +153,7 @@ class JsonDeserializer {
 
       // Parse value
       _nestingLimit--;
-      err = parseVariant(*slot->data());
+      err = parseVariant(*variant);
       _nestingLimit++;
       if (err) return err;