private void readExistingEntriesInto(Collection<String> services) {
      try {
        FileObject existing = getFiler()
            .getResource(StandardLocation.CLASS_OUTPUT, key.packageName, key.relativeName);
        try (Reader r = existing.openReader(true)) {
          for (String line : CharStreams.readLines(r)) {
            if (!SERVICE_FILE_COMMENT_LINE.matcher(line).find()) {
              services.add(line.trim());
            }
          }
        }
      } catch (Exception ex) {
        // unable to read existing file
      }
    }
Pragma-like comment indicator just at beginning of the source file used to disable import
post-processing.
generator/src/org/immutables/generator/Output.java