perf: skip unmodifiableMap wrapper when hookHints is empty (#1953)

* perf: skip unmodifiableMap wrapper when hookHints is empty

Signed-off-by: Tobias Ibounig <tobias.ibounig@dynatrace.com>

* ensure hookHints non null via builder, added test

Signed-off-by: Tobias Ibounig <tobias.ibounig@dynatrace.com>

* test null does not throw exception

Signed-off-by: Tobias Ibounig <tobias.ibounig@dynatrace.com>

* spotless

Signed-off-by: Tobias Ibounig <tobias.ibounig@dynatrace.com>

---------

Signed-off-by: Tobias Ibounig <tobias.ibounig@dynatrace.com>
Co-authored-by: Todd Baert <todd.baert@dynatrace.com>

Author: tobias-ibounig-dt

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

@@ -1,5 +1,6 @@
 package dev.openfeature.sdk;
 
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -19,4 +20,13 @@ public class FlagEvaluationOptions {
 
     @Builder.Default
     Map<String, Object> hookHints = new HashMap<>();
+
+    public static class FlagEvaluationOptionsBuilder {
+        /** Sets hook hints, normalizing null to an empty map. */
+        public FlagEvaluationOptionsBuilder hookHints(Map<String, Object> hookHints) {
+            this.hookHints$value = hookHints != null ? hookHints : Collections.emptyMap();
+            this.hookHints$set = true;
+            return this;
+        }
+    }
 }

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

@@ -172,7 +172,8 @@ private <T> FlagEvaluationDetails<T> evaluateFlag(
             flagOptions = options;
         }
 
-        hookSupportData.hints = Collections.unmodifiableMap(flagOptions.getHookHints());
+        var hookHints = flagOptions.getHookHints();
+        hookSupportData.hints = hookHints.isEmpty() ? Collections.emptyMap() : Collections.unmodifiableMap(hookHints);
         var context = new LayeredEvaluationContext(
                 openfeatureApi.getEvaluationContext(),
                 openfeatureApi.getTransactionContext(),

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

@@ -510,6 +510,27 @@ void missing_hook_hints() {
         assertTrue(feo.getHookHints().isEmpty());
     }
 
+    @Test
+    void null_hook_hints_does_not_throw() {
+        Hook hook = mockBooleanHook();
+        FeatureProvider provider = mock(FeatureProvider.class);
+        when(provider.getBooleanEvaluation(any(), any(), any()))
+                .thenReturn(ProviderEvaluation.<Boolean>builder().value(true).build());
+
+        api.setProviderAndWait(provider);
+        Client client = api.getClient();
+
+        assertThatCode(() -> client.getBooleanValue(
+                        "key",
+                        false,
+                        new ImmutableContext(),
+                        FlagEvaluationOptions.builder()
+                                .hook(hook)
+                                .hookHints(null)
+                                .build()))
+                .doesNotThrowAnyException();
+    }
+
     @Test
     void flag_eval_hook_order() {
         Hook hook = mockBooleanHook();