fix(fcm): Preserve unmapped TopicManagementResponse error reasons

src/main/java/com/google/firebase/messaging/TopicManagementResponse.java

@@ -37,10 +37,8 @@ public class TopicManagementResponse {
   // Server error codes as defined in https://developers.google.com/instance-id/reference/server
   // TODO: Should we handle other error codes here (e.g. PERMISSION_DENIED)?
   private static final Map<String, String> ERROR_CODES = ImmutableMap.<String, String>builder()
-      .put("INVALID_ARGUMENT", "invalid-argument")
       .put("NOT_FOUND", "registration-token-not-registered")
       .put("INTERNAL", "internal-error")
-      .put("TOO_MANY_TOPICS", "too-many-topics")
       .build();
 
   private final int successCount;
@@ -101,8 +99,11 @@ public static class Error {
 
     private Error(int index, String reason) {
       this.index = index;
-      this.reason = ERROR_CODES.containsKey(reason)
-        ? ERROR_CODES.get(reason) : UNKNOWN_ERROR;
+      if (reason == null || reason.trim().isEmpty()) {
+        this.reason = UNKNOWN_ERROR;
+      } else {
+        this.reason = ERROR_CODES.getOrDefault(reason, reason.toLowerCase().replace('_', '-'));
+      }
     }
 
     /**

src/test/java/com/google/firebase/messaging/InstanceIdClientImplTest.java

@@ -404,7 +404,30 @@ public void testTopicManagementResponseWithEmptyList() {
 
   @Test
   public void testTopicManagementResponseErrorToString() {
-    GenericJson json = new GenericJson().set("error", "test error");
+    GenericJson json = new GenericJson().set("error", "INVALID_ARGUMENT");
+    ImmutableList<GenericJson> jsonList = ImmutableList.of(json);
+
+    TopicManagementResponse topicManagementResponse = new TopicManagementResponse(jsonList);
+
+    String expected = "[Error{index=0, reason=invalid-argument}]";
+    assertEquals(expected, topicManagementResponse.getErrors().toString());
+  }
+
+  @Test
+  public void testTopicManagementResponseErrorNotInErrorCodes() {
+    String myError = "MY_ERROR";
+    GenericJson json = new GenericJson().set("error", myError);
+    ImmutableList<GenericJson> jsonList = ImmutableList.of(json);
+
+    TopicManagementResponse topicManagementResponse = new TopicManagementResponse(jsonList);
+
+    String expected = "[Error{index=0, reason=my-error}]";
+    assertEquals(expected, topicManagementResponse.getErrors().toString());
+  }
+
+  @Test
+  public void testTopicManagementResponseErrorUnknown() {
+    GenericJson json = new GenericJson().set("error", "");
     ImmutableList<GenericJson> jsonList = ImmutableList.of(json);
 
     TopicManagementResponse topicManagementResponse = new TopicManagementResponse(jsonList);
@@ -413,6 +436,29 @@ public void testTopicManagementResponseErrorToString() {
     assertEquals(expected, topicManagementResponse.getErrors().toString());
   }
 
+  @Test
+  public void testTopicManagementResponseErrorResourceExhausted() {
+    GenericJson json = new GenericJson().set("error", "RESOURCE_EXHAUSTED");
+    ImmutableList<GenericJson> jsonList = ImmutableList.of(json);
+
+    TopicManagementResponse topicManagementResponse = new TopicManagementResponse(jsonList);
+
+    String expected = "[Error{index=0, reason=resource-exhausted}]";
+    assertEquals(expected, topicManagementResponse.getErrors().toString());
+  }
+
+  @Test
+  public void testTopicManagementResponseErrorTooManyTopics() {
+    GenericJson json = new GenericJson().set("error", "TOO_MANY_TOPICS");
+    ImmutableList<GenericJson> jsonList = ImmutableList.of(json);
+
+    TopicManagementResponse topicManagementResponse = new TopicManagementResponse(jsonList);
+
+    String expected = "[Error{index=0, reason=too-many-topics}]";
+    assertEquals(expected, topicManagementResponse.getErrors().toString());
+  }
+
+
   private static InstanceIdClientImpl initInstanceIdClient(
       final MockLowLevelHttpResponse mockResponse,
       final HttpResponseInterceptor interceptor) {
@@ -432,7 +478,7 @@ private void checkTopicManagementRequest(
     assertEquals(1, result.getFailureCount());
     assertEquals(1, result.getErrors().size());
     assertEquals(1, result.getErrors().get(0).getIndex());
-    assertEquals("unknown-error", result.getErrors().get(0).getReason());
+    assertEquals("error-reason", result.getErrors().get(0).getReason());
 
     ByteArrayOutputStream out = new ByteArrayOutputStream();
     request.getContent().writeTo(out);