public void onTopicEdited()

in src/main/java/com/googlesource/gerrit/plugins/automerger/DownstreamCreator.java [122:181]
56 lines of code
10 McCabe index (conditional complexity)

  public void onTopicEdited(TopicEditedListener.Event event) {
    try (ManualRequestContext ctx = oneOffRequestContext.openAs(config.getContextUserId())) {
      ChangeInfo eventChange = event.getChange();
      // We have to re-query for this in order to include the current revision
      ChangeInfo change;
      try {
        change =
            gApi.changes()
                .id(eventChange._number)
                .get(EnumSet.of(ListChangesOption.CURRENT_REVISION));
      } catch (RestApiException e) {
        log.error("Automerger could not get change with current revision for onTopicEdited: ", e);
        return;
      }
      String oldTopic = event.getOldTopic();
      String revision = change.currentRevision;
      Set<String> downstreamBranches;
      try {
        downstreamBranches = config.getDownstreamBranches(change.branch, change.project);
      } catch (RestApiException | IOException | ConfigInvalidException e) {
        log.error("Failed to edit downstream topics of {}", change.id, e);
        return;
      }

      if (downstreamBranches.isEmpty()) {
        log.debug("Downstream branches of {} on {} are empty", change.branch, change.project);
        return;
      }

      // If change is empty, prevent someone breaking topic.
      if (isNullOrEmpty(change.topic)) {
        try {
          gApi.changes().id(change._number).topic(oldTopic);
          ReviewInput reviewInput = new ReviewInput();
          reviewInput.message(
              "Automerger prevented the topic from changing. Topic can only be modified on "
                  + "non-automerger-created CLs to a non-empty value.");
          reviewInput.notify = NotifyHandling.NONE;
          gApi.changes().id(change._number).revision(CURRENT).review(reviewInput);
        } catch (RestApiException e) {
          log.error("Failed to prevent setting empty topic for automerger plugin.", e);
        }
      } else {
        for (String downstreamBranch : downstreamBranches) {
          try {
            List<Integer> existingDownstream =
                getExistingMergesOnBranch(revision, oldTopic, downstreamBranch);
            for (Integer changeNumber : existingDownstream) {
              log.debug("Setting topic {} on {}", change.topic, changeNumber);
              gApi.changes().id(changeNumber).topic(change.topic);
            }
          } catch (RestApiException | InvalidQueryParameterException e) {
            log.error("Failed to edit downstream topics of {}", change.id, e);
          }
        }
      }
    } catch (StorageException | ConfigInvalidException e) {
      log.error("Automerger plugin failed onTopicEdited for {}", event.getChange().id, e);
    }
  }