updating config helper to have descriptive exception in strict mode

Author: mhlidd

utils/config-utils/src/main/java/datadog/trace/config/inversion/ConfigHelper.java

@@ -15,7 +15,7 @@ private ConfigHelper() {}
 
   /** Config Inversion strictness policy for enforcement of undocumented environment variables */
   public enum StrictnessPolicy {
-    STRICT,
+    STRICT_TEST,
     WARNING,
     TEST;
 
@@ -142,8 +142,12 @@ public String getEnvironmentVariable(String name) {
         ConfigInversionMetricCollectorProvider.get().setUndocumentedEnvVarMetric(name);
       }
 
-      if (configInversionStrict == StrictnessPolicy.STRICT) {
-        return null; // If strict mode is enabled, return null for unsupported configs
+      if (configInversionStrict == StrictnessPolicy.STRICT_TEST) {
+        throw new IllegalArgumentException(
+            "Unsupported configuration: "
+                + name
+                + " is not in GeneratedSupportedConfigurations. "
+                + "Add it to metadata/supported-configurations.json or remove the usage.");
       }
     }
 

utils/config-utils/src/test/java/datadog/trace/config/inversion/ConfigHelperTest.java

@@ -62,7 +62,7 @@ static void setUp() {
             testSupported, testAliases, testAliasMapping, new HashMap<>());
     ConfigHelper.get().setConfigurationSource(testSource);
     strictness = ConfigHelper.get().configInversionStrictFlag();
-    ConfigHelper.get().setConfigInversionStrict(ConfigHelper.StrictnessPolicy.STRICT);
+    ConfigHelper.get().setConfigInversionStrict(ConfigHelper.StrictnessPolicy.STRICT_TEST);
   }
 
   @AfterAll
@@ -177,7 +177,7 @@ void testUnsupportedEnvWarningNotInTestMode() {
     assertEquals("banana", ConfigHelper.env("DD_FAKE_VAR"));
 
     // Cleanup
-    ConfigHelper.get().setConfigInversionStrict(ConfigHelper.StrictnessPolicy.STRICT);
+    ConfigHelper.get().setConfigInversionStrict(ConfigHelper.StrictnessPolicy.STRICT_TEST);
   }
 
   @Test