From 2a3b51ac3a3e377b19113f780420efa01893b487 Mon Sep 17 00:00:00 2001
From: Benoit Blanchon <github@benoitblanchon.fr>
Date: Sun, 20 Jan 2019 14:35:22 +0100
Subject: [PATCH] Fixed uninitialized variant in JsonDocument

---
 CHANGELOG.md                              |  2 ++
 src/ArduinoJson/Document/JsonDocument.hpp | 12 +++++--
 test/JsonDocument/CMakeLists.txt          |  1 +
 test/JsonDocument/isNull.cpp              | 39 +++++++++++++++++++++++
 4 files changed, 52 insertions(+), 2 deletions(-)
 create mode 100644 test/JsonDocument/isNull.cpp

diff --git a/CHANGELOG.md b/CHANGELOG.md
index a2e97771..254e9b87 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -14,6 +14,8 @@ HEAD
 * Added `nesting()` to `JsonArray`, `JsonDocument`, `JsonObject`, and `JsonVariant`
 * Replaced `JsonDocument::nestingLimit` with an additional parameter
   to `deserializeJson()` and `deserializeMsgPack()`
+* Fixed uninitialized variant in `JsonDocument`
+* Added `JsonDocument::isNull()`
 
 > ### BREAKING CHANGES
 > 
diff --git a/src/ArduinoJson/Document/JsonDocument.hpp b/src/ArduinoJson/Document/JsonDocument.hpp
index e3c2a446..e13493f5 100644
--- a/src/ArduinoJson/Document/JsonDocument.hpp
+++ b/src/ArduinoJson/Document/JsonDocument.hpp
@@ -37,6 +37,10 @@ class JsonDocument : public Visitable {
     return getVariant().template is<T>();
   }
 
+  bool isNull() const {
+    return getVariant().isNull();
+  }
+
   size_t memoryUsage() const {
     return _pool.size();
   }
@@ -65,9 +69,13 @@ class JsonDocument : public Visitable {
   }
 
  protected:
-  JsonDocument(MemoryPool pool) : _pool(pool) {}
+  JsonDocument(MemoryPool pool) : _pool(pool) {
+    _data.setNull();
+  }
 
-  JsonDocument(char* buf, size_t capa) : _pool(buf, capa) {}
+  JsonDocument(char* buf, size_t capa) : _pool(buf, capa) {
+    _data.setNull();
+  }
 
   void copy(const JsonDocument& src) {
     to<VariantRef>().set(src.as<VariantRef>());
diff --git a/test/JsonDocument/CMakeLists.txt b/test/JsonDocument/CMakeLists.txt
index f727b341..0eba8c25 100644
--- a/test/JsonDocument/CMakeLists.txt
+++ b/test/JsonDocument/CMakeLists.txt
@@ -5,6 +5,7 @@
 add_executable(JsonDocumentTests
 	DynamicJsonDocument.cpp
 	nesting.cpp
+	isNull.cpp
 	StaticJsonDocument.cpp
 )
 
diff --git a/test/JsonDocument/isNull.cpp b/test/JsonDocument/isNull.cpp
new file mode 100644
index 00000000..9b7a44c5
--- /dev/null
+++ b/test/JsonDocument/isNull.cpp
@@ -0,0 +1,39 @@
+// ArduinoJson - arduinojson.org
+// Copyright Benoit Blanchon 2014-2018
+// MIT License
+
+#include <ArduinoJson.h>
+#include <catch.hpp>
+
+TEST_CASE("JsonDocument::isNull()") {
+  DynamicJsonDocument doc(4096);
+
+  SECTION("returns true if uninitialized") {
+    REQUIRE(doc.isNull() == true);
+  }
+
+  SECTION("returns false after to<JsonObject>()") {
+    doc.to<JsonObject>();
+    REQUIRE(doc.isNull() == false);
+  }
+
+  SECTION("returns false after to<JsonArray>()") {
+    doc.to<JsonArray>();
+    REQUIRE(doc.isNull() == false);
+  }
+
+  SECTION("returns true after to<JsonVariant>()") {
+    REQUIRE(doc.isNull() == true);
+  }
+
+  SECTION("returns false after set()") {
+    doc.to<JsonVariant>().set(42);
+    REQUIRE(doc.isNull() == false);
+  }
+
+  SECTION("returns true after clear()") {
+    doc.to<JsonObject>();
+    doc.clear();
+    REQUIRE(doc.isNull() == true);
+  }
+}