Address final feature flagging review feedback

Author: leoromanovsky

internal-api/build.gradle.kts

@@ -268,7 +268,7 @@ dependencies {
   api(project(":components:context"))
   api(project(":components:environment"))
   api(project(":components:json"))
-  api(project(":products:feature-flagging:feature-flagging-config"))
+  implementation(project(":products:feature-flagging:feature-flagging-config"))
   api(project(":utils:config-utils"))
   api(project(":utils:time-utils"))
 

internal-api/src/main/java/datadog/trace/api/Config.java

@@ -3802,7 +3802,21 @@ private static String normalizeFeatureFlaggingConfigurationSource(final String s
       return DEFAULT_FEATURE_FLAGGING_CONFIGURATION_SOURCE;
     }
     final String normalized = source.trim().toLowerCase(Locale.ROOT);
-    return normalized.isEmpty() ? DEFAULT_FEATURE_FLAGGING_CONFIGURATION_SOURCE : normalized;
+    if (normalized.isEmpty()) {
+      return DEFAULT_FEATURE_FLAGGING_CONFIGURATION_SOURCE;
+    }
+    switch (normalized) {
+      case "agentless":
+      case "remote_config":
+      case "offline":
+        return normalized;
+      default:
+        log.warn(
+            "Unsupported Feature Flagging configuration source: {}. Defaulting to {}",
+            source,
+            DEFAULT_FEATURE_FLAGGING_CONFIGURATION_SOURCE);
+        return DEFAULT_FEATURE_FLAGGING_CONFIGURATION_SOURCE;
+    }
   }
 
   public boolean isBaggageExtract() {

internal-api/src/test/groovy/datadog/trace/api/ConfigTest.groovy

@@ -3517,6 +3517,7 @@ class ConfigTest extends DDSpecification {
     ""                  | "agentless"
     "   "               | "agentless"
     " ReMoTe_ConFiG "   | "remote_config"
+    "not-a-real-source" | "agentless"
   }
 
   def "agentless feature flag timing falls back for non-positive values"() {

products/feature-flagging/feature-flagging-agent/build.gradle.kts

@@ -20,6 +20,7 @@ dependencies {
 
   testImplementation(libs.bundles.junit5)
   testImplementation(libs.bundles.mockito)
+  testImplementation(project(":products:feature-flagging:feature-flagging-config"))
   testImplementation(project(":utils:test-utils"))
   testRuntimeOnly(project(":dd-trace-core"))
 }

products/feature-flagging/feature-flagging-agent/src/test/java/com/datadog/featureflag/FeatureFlaggingSystemTest.java

@@ -97,12 +97,23 @@ void explicitRemoteConfigUsesRemoteConfigService() {
 
   @Test
   @WithConfig(key = FEATURE_FLAGS_CONFIGURATION_SOURCE, value = "invalid")
-  void invalidConfigurationSourceFailsBeforeStartingNetworkSource() {
+  void invalidConfigurationSourceUsesAgentlessDefault() {
+    assertInstanceOf(
+        AgentlessConfigurationSource.class,
+        FeatureFlaggingSystem.createConfigurationSourceService(
+            sharedCommunicationObjects(), Config.get()));
+  }
+
+  @Test
+  void rejectsUnsupportedNormalizedConfigurationSource() {
+    Config config = mock(Config.class);
+    when(config.getFeatureFlaggingConfigurationSource()).thenReturn("invalid");
+
     assertThrows(
         IllegalArgumentException.class,
         () ->
             FeatureFlaggingSystem.createConfigurationSourceService(
-                sharedCommunicationObjects(), Config.get()));
+                sharedCommunicationObjects(), config));
   }
 
   @Test