fix: [flagd]NPE of flagd due to null context value (#259)

Signed-off-by: Kavindu Dodanduwa <[email protected]>

Author: Kavindu-Dodan

providers/flagd/src/main/java/dev/openfeature/contrib/providers/flagd/FlagdProvider.java

@@ -16,6 +16,7 @@
 import com.google.protobuf.Descriptors.FieldDescriptor;
 import com.google.protobuf.Message;
 
+import com.google.protobuf.NullValue;
 import dev.openfeature.flagd.grpc.Schema.EventStreamRequest;
 import dev.openfeature.flagd.grpc.Schema.EventStreamResponse;
 import dev.openfeature.flagd.grpc.Schema.ResolveBooleanRequest;
@@ -386,7 +387,7 @@ private com.google.protobuf.Value convertPrimitive(Value value) {
         } else if (value.isNumber()) {
             builder.setNumberValue(value.asDouble());
         } else {
-            builder.setNullValue(null);
+            builder.setNullValue(NullValue.NULL_VALUE);
         }
         return builder.build();
     }
@@ -509,7 +510,7 @@ private Boolean cacheAvailable() {
 
         return available;
     }
-    
+
     // a generic resolve method that takes a resolverRef and an optional converter lambda to transform the result
     private <ValT extends Object, ReqT extends Message, ResT extends Message> ProviderEvaluation<ValT> resolve(
             String key, EvaluationContext ctx, ReqT request, Function<ReqT, ResT> resolverRef,

providers/flagd/src/test/java/dev/openfeature/contrib/providers/flagd/FlagdProviderTest.java

@@ -1,6 +1,7 @@
 package dev.openfeature.contrib.providers.flagd;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotEquals;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.ArgumentMatchers.anyInt;
@@ -375,6 +376,36 @@ void context_is_parsed_and_passed_to_grpc_service() {
         assertEquals(DEFAULT.toString(), booleanDetails.getReason());
     }
 
+    @Test
+    // Validates null handling - https://github.com/open-feature/java-sdk-contrib/issues/258
+    void null_context_handling(){
+        // given
+        final String flagA = "flagA";
+        final boolean defaultVariant = false;
+        final boolean expectedVariant = true;
+
+        final MutableContext context = new MutableContext();
+        context.add("key", (String) null);
+
+        final ServiceBlockingStub serviceBlockingStubMock = mock(ServiceBlockingStub.class);
+        final ServiceStub serviceStubMock = mock(ServiceStub.class);
+
+        // when
+        when(serviceBlockingStubMock.withDeadlineAfter(anyLong(), any(TimeUnit.class)))
+                .thenReturn(serviceBlockingStubMock);
+        when(serviceBlockingStubMock.resolveBoolean(any()))
+                .thenReturn(ResolveBooleanResponse.newBuilder().setValue(expectedVariant).build());
+
+        OpenFeatureAPI.getInstance()
+                .setProvider(new FlagdProvider(serviceBlockingStubMock, serviceStubMock, "lru", 10, 1));
+
+        // then
+        final Boolean evaluation = api.getClient().getBooleanValue(flagA, defaultVariant, context);
+
+        assertNotEquals(evaluation, defaultVariant);
+        assertEquals(evaluation, expectedVariant);
+    }
+
     @Test
     void set_deadline_deadline_send_in_grpc() {
         long deadline = 1300;