Does Firestore support writing to document from Groovy objects?

[emmileaf]

Question:

Does the Firestore client library currently (or have plans to) support writing data to document from Groovy objects?

Context:

Spring Cloud GCP currently calls the client library to serialize objects and convert them into documents for Firestore, but have received an issue (GoogleCloudPlatform/spring-cloud-gcp#939) regarding Groovy objects which have additional hidden fields. In particular, the hidden field metaClass.additionalMetaMethods is of type array and cannot be serialized by CustomClassMapper.

Looking at the existing logic in CustomClassMapper to filter out transient fields, it seems like traversing the class hierarchy would reach the Superclass groovy.lang.MetaClassImpl before java.lang.Object. Unlike the User subclass’s metaClass field, these Superclass fields are not marked as transient and therefore getting serialized.

cc: @elefeint

Snippets to reproduce issue in Java:

User.groovy

class User {
   String id;
   String name;
   …
}

Application.java

public class Application {

  private final GroovyClassLoader loader;
  private final Firestore db;

  public Application() throws IOException {
    this.loader = new GroovyClassLoader(this.getClass().getClassLoader());
    this.db = FirestoreOptions.getDefaultInstance().getService();
  }

  public static void main(String[] args) throws Exception {
    Application app = new Application();
    app.writeDocumentFromObjectGroovy();
  }

  private void writeDocumentFromObjectGroovy() throws Exception {
    // Add document data with id "103" using a custom Groovy User class
    Class userClass = loader.parseClass(new File("src/main/groovy/", "User.groovy"));
    GroovyObject data =
        (GroovyObject)
            userClass
                .getDeclaredConstructor(String.class, String.class)
                .newInstance("103", "Carol");

    // The following line throws error below:
    WriteResult writeResult = this.db.collection("users").document("103").set(data).get();
  }
}

Error stack trace:

Exception in thread "main" java.lang.IllegalArgumentException: Could not serialize object. Serializing Arrays is not supported, please use Lists instead (found in field 'metaClass.additionalMetaMethods')
   at com.google.cloud.firestore.CustomClassMapper.serializeError(CustomClassMapper.java:606)
   at com.google.cloud.firestore.CustomClassMapper.serialize(CustomClassMapper.java:161)
   at com.google.cloud.firestore.CustomClassMapper.access$500(CustomClassMapper.java:53)
   at com.google.cloud.firestore.CustomClassMapper$BeanMapper.serialize(CustomClassMapper.java:969)
   at com.google.cloud.firestore.CustomClassMapper.serialize(CustomClassMapper.java:181)
   at com.google.cloud.firestore.CustomClassMapper.access$500(CustomClassMapper.java:53)
   at com.google.cloud.firestore.CustomClassMapper$BeanMapper.serialize(CustomClassMapper.java:969)
   at com.google.cloud.firestore.CustomClassMapper.serialize(CustomClassMapper.java:181)
   at com.google.cloud.firestore.CustomClassMapper.serialize(CustomClassMapper.java:104)
   at com.google.cloud.firestore.CustomClassMapper.convertToPlainJavaTypes(CustomClassMapper.java:79)
   at com.google.cloud.firestore.UpdateBuilder.set(UpdateBuilder.java:239)
   at com.google.cloud.firestore.UpdateBuilder.set(UpdateBuilder.java:221)
   at com.google.cloud.firestore.DocumentReference.set(DocumentReference.java:202)
   at Application.writeDocumentFromObjectGroovy(Application.java:40)
   at Application.main(Application.java:26)