fix: improve handling for INTERNAL

Author: diegomarquezp

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

@@ -88,6 +88,7 @@ public String toString() {
    *         <li>{@code CLIENT_REDIRECT_ERROR}: Problem handling HTTP redirects.
    *         <li>{@code CLIENT_AUTHENTICATION_ERROR}: Error during credential acquisition or
    *             application.
+   *         <li>{@code CLIENT_UNKNOWN_ERROR}: For all other errors unknown to the client.
    *       </ul>
    *   <li><b>Language-specific error type:</b> The class or struct name of the exception or error
    *       if available. This must be low-cardinality, meaning it returns the short name of the
@@ -103,7 +104,8 @@ public String toString() {
    */
   public static String extractErrorType(@Nullable Throwable error) {
     if (error == null) {
-      return null;
+      // No information about the error; we default to INTERNAL.
+      return ErrorType.INTERNAL.toString();
     }
 
     // 1. & 2. Extract error info reason or server status code

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

@@ -41,48 +41,8 @@ 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.
-   *
-   * <p>This value is determined based on the following priority:
-   *
-   * <ol>
-   *   <li><b>{@code google.rpc.ErrorInfo.reason}:</b> If the error response from the service
-   *       includes {@code google.rpc.ErrorInfo} details, the reason field (e.g.,
-   *       "RATE_LIMIT_EXCEEDED", "SERVICE_DISABLED") will be used. This offers the most precise
-   *       error cause.
-   *   <li><b>Specific Server Error Code:</b> If no {@code ErrorInfo.reason} is available, but a
-   *       server error code was received:
-   *       <ul>
-   *         <li>For HTTP: The HTTP status code (e.g., "403", "503").
-   *         <li>For gRPC: The gRPC status code name (e.g., "PERMISSION_DENIED", "UNAVAILABLE").
-   *       </ul>
-   *   <li><b>Client-Side Network/Operational Errors:</b> For errors occurring within the client
-   *       library or network stack, mapping to specific enum representations from {@link
-   *       ErrorTypeUtil.ErrorType}:
-   *       <ul>
-   *         <li>{@code CLIENT_TIMEOUT}: A client-configured timeout was reached.
-   *         <li>{@code CLIENT_CONNECTION_ERROR}: Failure to establish the network connection (DNS,
-   *             TCP, TLS).
-   *         <li>{@code CLIENT_REQUEST_ERROR}: Client-side issue forming or sending the request.
-   *         <li>{@code CLIENT_REQUEST_BODY_ERROR}: Error streaming the request body.
-   *         <li>{@code CLIENT_RESPONSE_DECODE_ERROR}: Client-side error decoding the response body.
-   *         <li>{@code CLIENT_REDIRECT_ERROR}: Problem handling HTTP redirects.
-   *         <li>{@code CLIENT_AUTHENTICATION_ERROR}: Error during credential acquisition or
-   *             application.
-   *         <li>{@code CLIENT_UNKNOWN_ERROR}: Other unclassified client-side network or protocol
-   *             errors.
-   *       </ul>
-   *   <li><b>Language-specific error type:</b> The class or struct name of the exception or error
-   *       if available. This must be low-cardinality, meaning it returns the short name of the
-   *       exception class (e.g. {@code "IllegalStateException"}) rather than its message.
-   *   <li><b>Internal Fallback:</b> If the error doesn't fit any of the above categories, {@code
-   *       "INTERNAL"} will be used, indicating an unexpected issue within the client library's own
-   *       logic.
-   * </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}.
+   * 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);

gax-java/gax/src/main/java/com/google/api/gax/tracing/SpanTracer.java

@@ -107,11 +107,8 @@ public void attemptPermanentFailure(Throwable error) {
 
   private void recordErrorAndEndAttempt(Throwable error) {
     if (attemptHandle != null) {
-      if (error != null) {
-        attemptHandle.addAttribute(
-            ObservabilityAttributes.ERROR_TYPE_ATTRIBUTE,
-            ObservabilityUtils.extractErrorType(error));
-      }
+      attemptHandle.addAttribute(
+          ObservabilityAttributes.ERROR_TYPE_ATTRIBUTE, ObservabilityUtils.extractErrorType(error));
       endAttempt();
     }
   }

gax-java/gax/src/test/java/com/google/api/gax/tracing/SpanTracerTest.java

@@ -330,6 +330,23 @@ void testAttemptFailed_internalFallback() {
     verify(attemptHandle).end();
   }
 
+  @Test
+  void testAttemptFailed_internalFallback_nullError() {
+    when(recorder.createSpan(eq(ATTEMPT_SPAN_NAME), anyMap())).thenReturn(attemptHandle);
+
+    tracer.attemptStarted(new Object(), 1);
+
+    tracer.attemptFailedRetriesExhausted(null);
+
+    // For an anonymous inner class Throwable, getSimpleName() is empty string, which triggers the
+    // fallback
+    verify(attemptHandle)
+        .addAttribute(
+            ObservabilityAttributes.ERROR_TYPE_ATTRIBUTE,
+            ErrorTypeUtil.ErrorType.INTERNAL.toString());
+    verify(attemptHandle).end();
+  }
+
   private static class TestGoogleAuthException extends RuntimeException {}
 
   private static class RedirectException extends RuntimeException {