fix: possible StackOverflow on recursive contexts (#1760)

* Fix StackOverflow on recursive contexts

Signed-off-by: christian.lutnik <christian.lutnik@dynatrace.com>

* Fix StackOverflow on recursive contexts

Signed-off-by: christian.lutnik <christian.lutnik@dynatrace.com>

* Fix StackOverflow on recursive contexts

Signed-off-by: christian.lutnik <christian.lutnik@dynatrace.com>

---------

Signed-off-by: christian.lutnik <christian.lutnik@dynatrace.com>
Co-authored-by: Todd Baert <todd.baert@dynatrace.com>

Author: chrfwow

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

@@ -63,7 +63,8 @@ public void executeBeforeHooks(HookSupportData data) {
                     .orElse(Optional.empty());
             if (returnedEvalContext.isPresent()) {
                 var returnedContext = returnedEvalContext.get();
-                if (!returnedContext.isEmpty()) {
+                // yes, we want to check for reference equality here, this prevents recursive layered contexts
+                if (returnedContext != hookContext.getCtx() && !returnedContext.isEmpty()) {
                     data.evaluationContext.putHookContext(returnedContext);
                 }
             }

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

@@ -1,6 +1,7 @@
 package dev.openfeature.sdk;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatNoException;
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.verify;
@@ -113,6 +114,33 @@ void shouldIsolateDataBetweenHooks(FlagValueType flagValueType) {
         assertHookData(testHook2, 2, "before", "after", "finallyAfter", "error");
     }
 
+    @Test
+    void hookThatReturnsTheGivenContext_doesNotResultInAStackOverflow() {
+        var hookSupportData = new HookSupportData();
+        var recursiveHook = new Hook() {
+            @Override
+            public Optional<EvaluationContext> before(HookContext ctx, Map hints) {
+                return Optional.of(ctx.getCtx());
+            }
+        };
+        var emptyHook = new Hook() {
+            @Override
+            public Optional<EvaluationContext> before(HookContext ctx, Map hints) {
+                return Optional.of(ImmutableContext.EMPTY);
+            }
+        };
+        var layeredEvaluationContext =
+                new LayeredEvaluationContext(evaluationContextWithValue("key", "value"), null, null, null);
+        hookSupportData.evaluationContext = layeredEvaluationContext;
+        hookSupport.setHooks(hookSupportData, List.of(recursiveHook, emptyHook), FlagValueType.STRING);
+        hookSupport.setHookContexts(
+                hookSupportData, getBaseHookContextForType(FlagValueType.STRING), layeredEvaluationContext);
+
+        callAllHooks(hookSupportData);
+
+        assertThatNoException().isThrownBy(layeredEvaluationContext::asObjectMap);
+    }
+
     private static void callAllHooks(HookSupportData hookSupportData) {
         hookSupport.executeBeforeHooks(hookSupportData);
         hookSupport.executeAfterHooks(