Add Locale.ROOT to ConfigStrings Environment Variable Normalization

dd-java-agent/instrumentation-testing/src/main/groovy/datadog/trace/agent/test/InstrumentationSpecification.groovy

@@ -124,7 +124,7 @@ abstract class InstrumentationSpecification extends DDSpecification implements A
     StringBuilder ddEnvVars = new StringBuilder()
     for (Map.Entry<Object, Object> entry : System.getProperties().entrySet()) {
       if (entry.getKey().toString().startsWith("dd.")) {
-        ddEnvVars.append(ConfigStrings.systemPropertyNameToEnvironmentVariableName(entry.getKey().toString()))
+        ddEnvVars.append(ConfigStrings.toEnvVar(entry.getKey().toString()))
         .append("=").append(entry.getValue()).append(",")
       }
     }

utils/config-utils/src/main/java/datadog/trace/util/ConfigStrings.java

@@ -1,17 +1,18 @@
 package datadog.trace.util;
 
+import java.util.Locale;
 import javax.annotation.Nonnull;
 
 public final class ConfigStrings {
 
   private ConfigStrings() {}
 
   public static String toEnvVar(String string) {
-    return string.replace('.', '_').replace('-', '_').toUpperCase();
+    return string.replace('.', '_').replace('-', '_').toUpperCase(Locale.ROOT);
   }
 
   public static String toEnvVarLowerCase(String string) {
-    return string.replace('.', '_').replace('-', '_').toLowerCase();
+    return string.replace('.', '_').replace('-', '_').toLowerCase(Locale.ROOT);
   }
 
   /**
@@ -26,18 +27,6 @@ public static String propertyNameToEnvironmentVariableName(final String setting)
     return "DD_" + toEnvVar(setting);
   }
 
-  /**
-   * Converts the system property name, e.g. 'dd.service.name' into a public environment variable
-   * name, e.g. `DD_SERVICE_NAME`.
-   *
-   * @param setting The system property name, e.g. `dd.service.name`
-   * @return The public facing environment variable name
-   */
-  @Nonnull
-  public static String systemPropertyNameToEnvironmentVariableName(final String setting) {
-    return setting.replace('.', '_').replace('-', '_').toUpperCase();
-  }
-
   /**
    * Converts the property name, e.g. 'service.name' into a public system property name, e.g.
    * `dd.service.name`.

utils/config-utils/src/test/java/datadog/trace/util/ConfigStringsTest.java

@@ -0,0 +1,33 @@
+package datadog.trace.util;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+
+import java.util.Locale;
+import org.junit.jupiter.api.Test;
+
+class ConfigStringsTest {
+
+  /** Dotted capital I (U+0130) that a Turkish-locale {@code toUpperCase()} produces from 'i'. */
+  private static final char DOTTED_CAPITAL_I = 'İ';
+
+  @Test
+  void toEnvVarUppercasesLowerIToAsciiIOnTurkishLocale() {
+    // Turkish is the locale where a locale-sensitive toUpperCase() maps 'i' -> 'İ'
+    // Forcing it as the default locale here proves the conversions are
+    // locale-independent (pinned to Locale.ROOT) rather than relying on the machine's locale.
+    Locale previousDefault = Locale.getDefault();
+    Locale.setDefault(new Locale("tr", "TR"));
+    try {
+      String result = ConfigStrings.toEnvVar("dd.profiling.i");
+
+      // Must be the plain ASCII 'I' (U+0049), not the Turkish dotted 'İ' (U+0130).
+      assertEquals("DD_PROFILING_I", result);
+      assertFalse(
+          result.indexOf(DOTTED_CAPITAL_I) >= 0,
+          "env var name must not contain the dotted capital I (U+0130)");
+    } finally {
+      Locale.setDefault(previousDefault);
+    }
+  }
+}