Using reference-equality Set for unionSchemas. It makes for simples code.

Author: MichalFoksa

avro/src/main/java/com/fasterxml/jackson/dataformat/avro/schema/RecordVisitor.java

@@ -1,6 +1,7 @@
 package com.fasterxml.jackson.dataformat.avro.schema;
 
 import java.util.*;
+import java.util.stream.Collectors;
 
 import org.apache.avro.LogicalTypes;
 import org.apache.avro.Schema;
@@ -85,56 +86,30 @@ public RecordVisitor(SerializerProvider p, JavaType type, VisitorFormatWrapperIm
 
             List<NamedType> subTypes = getProvider().getAnnotationIntrospector().findSubtypes(bean.getClassInfo());
             if (subTypes != null && !subTypes.isEmpty()) {
-
                 // At this point calculating hashCode for _typeSchema fails with NPE because RecordSchema.fields is NULL
-                // (see org.apache.avro.Schema.RecordSchema#computeHash).
-                // Therefore, _typeSchema must be added into union at very end, or unionSchemas must not be HashSet (or any
-                // other type calling hashCode() for equality check).
-                Set<Schema> unionSchemas = new HashSet<>();
-                // ArrayList<Schema> unionSchemas = new ArrayList<>();
-
+                // see org.apache.avro.Schema.RecordSchema#computeHash.
+                // Therefore, unionSchemas must not be HashSet (or any other type using hashCode() for equality check).
                 // IdentityHashMap is used because it is using reference-equality.
-                // Set<Schema> unionSchemas = Collections.newSetFromMap(new IdentityHashMap<>());
-
-                // Initialize with this schema is
-                // if (_type.isConcrete()) {
-                //   unionSchemas.add(_typeSchema);
-                // }
-
+                Set<Schema> unionSchemas = Collections.newSetFromMap(new IdentityHashMap<>());
+                // Initialize with this schema
+                if (_type.isConcrete()) {
+                    unionSchemas.add(_typeSchema);
+                }
                 try {
                     for (NamedType subType : subTypes) {
                         JsonSerializer<?> ser = getProvider().findValueSerializer(subType.getType());
                         VisitorFormatWrapperImpl visitor = _visitorWrapper.createChildWrapper();
                         ser.acceptJsonFormatVisitor(visitor, getProvider().getTypeFactory().constructType(subType.getType()));
-                        Schema subTypeSchema = visitor.getAvroSchema();
                         // Add subType schema into this union, unless it is already there.
+                        Schema subTypeSchema = visitor.getAvroSchema();
                         // When subType schema is union itself, include each its type into this union if not there already
                         if (subTypeSchema.getType() == Type.UNION) {
-//                            subTypeSchema.getTypes().stream()
-//                                    .filter(unionElement -> !unionSchemas.contains(unionElement))
-//                                    .forEach(unionSchemas::add);
-                            // or
-//                            for( Schema unionElement: subTypeSchema.getTypes()) {
-//                                if (unionSchemas.contains(unionElement)) {
-//                                    continue;
-//                                }
-//                                unionSchemas.add(unionElement);
-//                            }
                             unionSchemas.addAll(subTypeSchema.getTypes());
                         } else {
-//                            if (!unionSchemas.contains(subTypeSchema)) {
-//                                unionSchemas.add(subTypeSchema);
-//                            }
                             unionSchemas.add(subTypeSchema);
                         }
                     }
-
-                    ArrayList<Schema> unionList = new ArrayList<>(unionSchemas);
-                    // add _type schema into union
-                    if (_type.isConcrete()) {
-                        unionList.add(_typeSchema);
-                    }
-                    _avroSchema = Schema.createUnion(unionList);
+                    _avroSchema = Schema.createUnion(new ArrayList<>(unionSchemas));
                 } catch (JsonMappingException jme) {
                     throw new RuntimeException("Failed to build schema", jme);
                 }