From 367d721212f8f57d86c0a705da479e5ed2df80ec Mon Sep 17 00:00:00 2001
From: timtay-microsoft <timtay@microsoft.com>
Date: Mon, 23 Apr 2018 13:32:51 -0700
Subject: [PATCH] fix(iot-service): Fix bug where setting desired properties to
 null didn't delete them from the device

Github Bug #221
---
 .../azure/sdk/iot/deps/twin/TwinState.java    | 12 +++++-
 .../sdk/iot/deps/twin/TwinStateTest.java      | 41 +++++++++++++++++--
 2 files changed, 49 insertions(+), 4 deletions(-)

diff --git a/deps/src/main/java/com/microsoft/azure/sdk/iot/deps/twin/TwinState.java b/deps/src/main/java/com/microsoft/azure/sdk/iot/deps/twin/TwinState.java
index a91a3e6ea4..15cd9077a0 100644
--- a/deps/src/main/java/com/microsoft/azure/sdk/iot/deps/twin/TwinState.java
+++ b/deps/src/main/java/com/microsoft/azure/sdk/iot/deps/twin/TwinState.java
@@ -175,7 +175,17 @@ public JsonElement toJsonElement()
         /* SRS_TWIN_STATE_21_003: [If the tags is null, the toJsonElement shall not include the `tags` in the final JSON.] */
         /* SRS_TWIN_STATE_21_004: [If the property is null, the toJsonElement shall not include the `properties` in the final JSON.] */
         Gson gson = new GsonBuilder().disableHtmlEscaping().create();
-        return gson.toJsonTree(this).getAsJsonObject();
+        JsonElement json = gson.toJsonTree(this).getAsJsonObject();
+
+        //since null values are lost when building the json tree, need to manually re-add properties as reported properties
+        // may have contained a property with a null value. Those must be preserved so users can delete properties
+        if (json != null && this.properties != null)
+        {
+            //Codes_SRS_TWIN_STATE_34_024: [The json element shall include all null desired and reported properties.]
+            json.getAsJsonObject().add("properties", this.properties.toJsonElement());
+        }
+
+        return json;
     }
 
     /**
diff --git a/deps/src/test/java/tests/unit/com/microsoft/azure/sdk/iot/deps/twin/TwinStateTest.java b/deps/src/test/java/tests/unit/com/microsoft/azure/sdk/iot/deps/twin/TwinStateTest.java
index 3cdbb1bed6..3c3f87c461 100644
--- a/deps/src/test/java/tests/unit/com/microsoft/azure/sdk/iot/deps/twin/TwinStateTest.java
+++ b/deps/src/test/java/tests/unit/com/microsoft/azure/sdk/iot/deps/twin/TwinStateTest.java
@@ -12,9 +12,7 @@
 import org.junit.Test;
 import tests.unit.com.microsoft.azure.sdk.iot.deps.Helpers;
 
-import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertNotNull;
-import static org.junit.Assert.assertNull;
+import static org.junit.Assert.*;
 
 /**
  * Unit tests for the TwinState
@@ -40,6 +38,15 @@ public class TwinStateTest
         }
     };
 
+    private final static TwinCollection PROPERTIES_WITH_NULL_VALUES = new TwinCollection()
+    {
+        {
+            put("prop1", null);
+            put("prop2", null);
+            put("prop3", null);
+        }
+    };
+
     private final static String REGISTER_MANAGER_SAMPLE =
             "\"deviceId\":\"validDeviceId\"," +
             "\"generationId\":\"validGenerationId\"," +
@@ -222,6 +229,34 @@ public void toJsonElementReturnsEmptyJson()
         Helpers.assertJson(jsonElement.toString(), "{}");
     }
 
+    //Tests_SRS_TWIN_STATE_34_024: [The json element shall include all null desired and reported properties.]
+    @Test
+    public void toJsonElementPreservesNullDesiredProperties()
+    {
+        // arrange
+        TwinState twinState = new TwinState(null, PROPERTIES_WITH_NULL_VALUES, PROPERTIES);
+
+        // act
+        JsonElement jsonElement = Deencapsulation.invoke(twinState, "toJsonElement");
+
+        // assert
+        assertTrue(jsonElement.toString().contains(PROPERTIES_WITH_NULL_VALUES.toString()));
+    }
+
+    //Tests_SRS_TWIN_STATE_34_024: [The json element shall include all null desired and reported properties.]
+    @Test
+    public void toJsonElementPreservesNullReportedProperties()
+    {
+        // arrange
+        TwinState twinState = new TwinState(null, PROPERTIES, PROPERTIES_WITH_NULL_VALUES);
+
+        // act
+        JsonElement jsonElement = Deencapsulation.invoke(twinState, "toJsonElement");
+
+        // assert
+        assertTrue(jsonElement.toString().contains(PROPERTIES_WITH_NULL_VALUES.toString()));
+    }
+
     /* SRS_TWIN_STATE_21_005: [The getTags shall return a TwinCollection with the stored tags.] */
     /* SRS_TWIN_STATE_21_006: [The getDesiredProperty shall return a TwinCollection with the stored desired property.] */
     /* SRS_TWIN_STATE_21_007: [The getReportedProperty shall return a TwinCollection with the stored reported property.] */