fixed the implementation of key set method in the ImmutableStructure

Signed-off-by: thiyagu06 <[email protected]>

Author: thiyagu06

src/main/java/dev/openfeature/sdk/ImmutableStructure.java

@@ -1,12 +1,10 @@
 package dev.openfeature.sdk;
 
 import lombok.EqualsAndHashCode;
-import lombok.SneakyThrows;
 import lombok.ToString;
 
-import java.time.Instant;
 import java.util.HashMap;
-import java.util.List;
+import java.util.HashSet;
 import java.util.Map;
 import java.util.Set;
 import java.util.stream.Collectors;
@@ -45,7 +43,7 @@ public ImmutableStructure(Map<String, Value> attributes) {
 
     @Override
     public Set<String> keySet() {
-        return this.attributes.keySet();
+        return new HashSet<>(this.attributes.keySet());
     }
 
     // getters

src/main/java/dev/openfeature/sdk/Value.java

@@ -17,7 +17,7 @@
 @ToString
 @EqualsAndHashCode
 @SuppressWarnings({"PMD.BeanMembersShouldSerialize", "checkstyle:MissingJavadocType"})
-public class Value implements Cloneable{
+public class Value implements Cloneable {
 
     private final Object innerObject;
 

src/test/java/dev/openfeature/sdk/ImmutableStructureTest.java

@@ -8,6 +8,7 @@
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
 
 import static org.junit.jupiter.api.Assertions.assertArrayEquals;
 import static org.junit.jupiter.api.Assertions.assertEquals;
@@ -93,4 +94,18 @@ class ImmutableStructureTest {
         assertEquals(1, structure.getValue(KEY).asStructure().asMap().get("list").asList().size());
         assertEquals("dummy_list_1", structure.getValue(KEY).asStructure().asMap().get("list").asList().get(0).asString());
     }
+
+    @Test
+    void ModifyingTheValuesReturnByTheKeySetMethodShouldNotModifyTheUnderlyingImmutableStructure() {
+        Map<String, Value> map = new HashMap<String, Value>() {
+            {
+                put("key", new Value(10));
+                put("key1", new Value(20));
+            }
+        };
+        ImmutableStructure structure = new ImmutableStructure(map);
+        Set<String> keys = structure.keySet();
+        keys.remove("key1");
+        assertEquals(2, structure.keySet().size());
+    }
 }