From cf56a7de2a80fe46bd823c62997838cc905a9ddb Mon Sep 17 00:00:00 2001
From: Benoit Blanchon <git@benoitblanchon.fr>
Date: Fri, 11 Mar 2022 18:28:37 +0100
Subject: [PATCH] isNull()

---
 extras/tests/JsonVariant/isnull.cpp     | 35 +++++++++++++++++--------
 src/ArduinoJson/Variant/VariantData.hpp |  2 ++
 2 files changed, 26 insertions(+), 11 deletions(-)

diff --git a/extras/tests/JsonVariant/isnull.cpp b/extras/tests/JsonVariant/isnull.cpp
index 7e29039f..ec5e0a34 100644
--- a/extras/tests/JsonVariant/isnull.cpp
+++ b/extras/tests/JsonVariant/isnull.cpp
@@ -9,17 +9,17 @@ TEST_CASE("JsonVariant::isNull()") {
   DynamicJsonDocument doc(4096);
   JsonVariant variant = doc.to<JsonVariant>();
 
-  SECTION("return true when Undefined") {
+  SECTION("returns true when Undefined") {
     REQUIRE(variant.isNull() == true);
   }
 
-  SECTION("return false when Integer") {
+  SECTION("returns false when Integer") {
     variant.set(42);
 
     REQUIRE(variant.isNull() == false);
   }
 
-  SECTION("return false when EmptyArray") {
+  SECTION("returns false when EmptyArray") {
     DynamicJsonDocument doc2(4096);
     JsonArray array = doc2.to<JsonArray>();
 
@@ -27,7 +27,7 @@ TEST_CASE("JsonVariant::isNull()") {
     REQUIRE(variant.isNull() == false);
   }
 
-  SECTION("return false when EmptyObject") {
+  SECTION("returns false when EmptyObject") {
     DynamicJsonDocument doc2(4096);
     JsonObject obj = doc2.to<JsonObject>();
 
@@ -35,41 +35,54 @@ TEST_CASE("JsonVariant::isNull()") {
     REQUIRE(variant.isNull() == false);
   }
 
-  SECTION("return true after set(JsonArray())") {
+  SECTION("returns true after set(JsonArray())") {
     variant.set(JsonArray());
     REQUIRE(variant.isNull() == true);
   }
 
-  SECTION("return true after set(JsonObject())") {
+  SECTION("returns true after set(JsonObject())") {
     variant.set(JsonObject());
     REQUIRE(variant.isNull() == true);
   }
 
-  SECTION("return false after set('hello')") {
+  SECTION("returns false after set('hello')") {
     variant.set("hello");
     REQUIRE(variant.isNull() == false);
   }
 
-  SECTION("return true after set((char*)0)") {
+  SECTION("returns true after set((char*)0)") {
     variant.set(static_cast<char*>(0));
     REQUIRE(variant.isNull() == true);
   }
 
-  SECTION("return true after set((const char*)0)") {
+  SECTION("returns true after set((const char*)0)") {
     variant.set(static_cast<const char*>(0));
     REQUIRE(variant.isNull() == true);
   }
 
-  SECTION("return true after set(serialized((char*)0))") {
+  SECTION("returns true after set(serialized((char*)0))") {
     variant.set(serialized(static_cast<char*>(0)));
     REQUIRE(variant.isNull() == true);
   }
 
-  SECTION("return true after set(serialized((const char*)0))") {
+  SECTION("returns true after set(serialized((const char*)0))") {
     variant.set(serialized(static_cast<const char*>(0)));
     REQUIRE(variant.isNull() == true);
   }
 
+  SECTION("returns true for a linked null") {
+    StaticJsonDocument<128> doc2;
+    variant.link(doc2);
+    CHECK(variant.isNull() == true);
+  }
+
+  SECTION("returns false for a linked array") {
+    StaticJsonDocument<128> doc2;
+    doc2[0] = 42;
+    variant.link(doc2);
+    CHECK(variant.isNull() == false);
+  }
+
   SECTION("works with JsonVariantConst") {
     variant.set(42);
 
diff --git a/src/ArduinoJson/Variant/VariantData.hpp b/src/ArduinoJson/Variant/VariantData.hpp
index 213f2a00..d872c964 100644
--- a/src/ArduinoJson/Variant/VariantData.hpp
+++ b/src/ArduinoJson/Variant/VariantData.hpp
@@ -165,6 +165,8 @@ class VariantData {
   }
 
   bool isNull() const {
+    if (isPointer())
+      return _content.asPointer->isNull();
     return type() == VALUE_IS_NULL;
   }