[GitHub] [beam] andreigurau commented on a diff in pull request #17477: [BEAM-10265] Display error message if trying to infer recursive schema from POJO/Proto objects

[GitBox <gi...@apache.org>]

andreigurau commented on code in PR #17477:
URL: https://github.com/apache/beam/pull/17477#discussion_r861041123


##########
sdks/java/core/src/main/java/org/apache/beam/sdk/schemas/utils/StaticSchemaInference.java:
##########
@@ -87,22 +88,33 @@ enum MethodType {
    * public getter methods, or special annotations on the class.
    */
   public static Schema schemaFromClass(
-      Class<?> clazz, FieldValueTypeSupplier fieldValueTypeSupplier) {
+      Class<?> clazz,
+      FieldValueTypeSupplier fieldValueTypeSupplier,
+      HashSet<Class> alreadyVisitedSchemas) {
+    if (alreadyVisitedSchemas.contains(clazz)) {
+      throw new RuntimeException(
+          "Cannot infer schema with a circular reference. Class: " + clazz.getTypeName());
+    }
+    alreadyVisitedSchemas.add(clazz);
     Schema.Builder builder = Schema.builder();
     for (FieldValueTypeInformation type : fieldValueTypeSupplier.get(clazz)) {
-      Schema.FieldType fieldType = fieldFromType(type.getType(), fieldValueTypeSupplier);
+      Schema.FieldType fieldType =
+          fieldFromType(type.getType(), fieldValueTypeSupplier, alreadyVisitedSchemas);
       if (type.isNullable()) {
         builder.addNullableField(type.getName(), fieldType);
       } else {
         builder.addField(type.getName(), fieldType);
       }
     }
+    alreadyVisitedSchemas.remove(clazz);

Review Comment:
   > It might be possible that multiple types nested under the same type reference each other in a non-circular way.
   
   I'm not following what you mean here, do you have an example?



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