AvroSchemaCompatibilityOfEnumsWithDefault.scala

// In build.sbt: libraryDependencies += "org.apache.avro" % "avro" % "1.11.0"

/*

In org.apache.avro library there are two different versions of checking schema compatibility:

  (1) SchemaValidator.validate
  (2) SchemaComatibility.checkReaderWriterCompatibility

The first is deprecated, and not aligned with the second (for example changes to enums are completely ignored in (1)).

Interestingly it was only very recently (Feb 2021) that the Confluent schema-registry switched over to using (2):
https://github.com/confluentinc/schema-registry/pull/1775

*/

import org.apache.avro.Schema
import org.apache.avro.SchemaCompatibility

object AvroSchemaCompatibilityOfEnumsWithDefault {

  def main(args: Array[String]) {
    println(
      "Messages produced by schema_0 can be read by schema_1: " + 
        isForwardsCompatible(schema_0, schema_1)
    ) // true
    println(
      "Messages produced by schema_1 can be read by schema_0: " + 
        isForwardsCompatible(schema_1, schema_0)
    ) // true (but arguably should be false)
  }

  def isForwardsCompatible(writer: Schema, reader: Schema): Boolean =
    SchemaCompatibility
      .checkReaderWriterCompatibility(reader, writer)
      .getResult
      .getIncompatibilities
      .isEmpty

  val schema_0 = Schema.parse(
    """ 
    |{
    |   "type":"record",
    |   "name":"Form",
    |   "fields":[
    |      {
    |         "name":"rating",
    |         "type":
    |           {
    |               "type":"enum",
    |               "name":"Rating",
    |               "symbols":[
    |                  "Excellent",
    |                  "Good",
    |                  "Bad"
    |               ],
    |               "default": "Good" 
    |            }
    |       }
    |   ]
    |}
    """.stripMargin
  )
    
  val schema_1 = Schema.parse(
    """ 
    |{
    |   "type":"record",
    |   "name":"Form",
    |   "fields":[
    |      {
    |         "name":"rating",
    |         "type":
    |           {
    |               "type":"enum",
    |               "name":"Rating",
    |               "symbols":[
    |                  "Perfect",
    |                  "Excellent",
    |                  "Good",
    |                  "Bad"
    |               ],
    |               "default": "Good"
    |            }
    |       }
    |   ]
    |}
    """.stripMargin
  )

}