fix: make extractErrorType nonnull

Author: blakeli0

sdk-platform-java/gax-java/gax/src/main/java/com/google/api/gax/tracing/ErrorTypeUtil.java

@@ -43,6 +43,7 @@
 import java.nio.channels.UnresolvedAddressException;
 import java.security.GeneralSecurityException;
 import java.util.Set;
+import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
 import javax.net.ssl.SSLHandshakeException;
 
@@ -112,15 +113,10 @@ enum ErrorType {
    * </ol>
    *
    * @param error the Throwable from which to extract the error type string.
-   * @return a low-cardinality string representing the specific error type, or {@code null} if the
-   *     provided error is {@code null} or non-determined.
+   * @return a low-cardinality string representing the specific error type
    */
   // Requirement source: go/clo:product-requirements-v1
-  public static String extractErrorType(@Nullable Throwable error) {
-    if (error == null) {
-      // No information about the error; return null so the attribute is not recorded.
-      return null;
-    }
+  public static String extractErrorType(@Nonnull Throwable error) {
 
     // 1. Unwrap standard wrapper exceptions if present
     Throwable realError = getRealCause(error);

sdk-platform-java/gax-java/gax/src/main/java/com/google/api/gax/tracing/ObservabilityUtils.java

@@ -44,15 +44,6 @@
 
 final class ObservabilityUtils {
 
-  /**
-   * Extracts a low-cardinality string representing the specific classification of the error to be
-   * used in the {@link ObservabilityAttributes#ERROR_TYPE_ATTRIBUTE} attribute. See {@link
-   * ErrorTypeUtil#extractErrorType} for extended documentation.
-   */
-  static String extractErrorType(@Nullable Throwable error) {
-    return ErrorTypeUtil.extractErrorType(error);
-  }
-
   /** Function to extract the status of the error as a canonical code. */
   static StatusCode.Code extractStatus(@Nullable Throwable error) {
     if (error == null) {
@@ -182,7 +173,7 @@ static Map<String, Object> getResponseAttributes(
     }
     if (error != null) {
       attributes.put(
-          ObservabilityAttributes.ERROR_TYPE_ATTRIBUTE, ObservabilityUtils.extractErrorType(error));
+          ObservabilityAttributes.ERROR_TYPE_ATTRIBUTE, ErrorTypeUtil.extractErrorType(error));
       attributes.put(ObservabilityAttributes.EXCEPTION_TYPE_ATTRIBUTE, error.getClass().getName());
     }
     return attributes;

sdk-platform-java/gax-java/gax/src/test/java/com/google/api/gax/tracing/ErrorTypeUtilTest.java

@@ -51,11 +51,6 @@
 
 class ErrorTypeUtilTest {
 
-  @Test
-  void testExtractErrorType_null() {
-    assertThat(ErrorTypeUtil.extractErrorType(null)).isNull();
-  }
-
   @Test
   void testExtractErrorType_apiException_noReason() {
     ApiException exception =