THRIFT-5571: add metadata map building to kotlin generator

[jimexist]

add metadata map building to kotlin generator

• Did you create an Apache Jira ticket? (not required for trivial changes)
• If a ticket exists: Does your pull request title follow the pattern "THRIFT-NNNN: describe my issue"?
• Did you squash your changes to a single commit? (not required, but preferred)
• Did you do your best to avoid breaking changes? If one was needed, did you label the Jira ticket with "Breaking-Change"?
• If your change does not involve any code, include [skip ci] anywhere in the commit message to free up build resources.

code generation example:

Bonk.kt

/**
 * Autogenerated by Thrift Compiler (0.17.0)
 *
 * DO NOT EDIT UNLESS YOU ARE SURE THAT YOU KNOW WHAT YOU ARE DOING
 *  @generated
 */
@file:Suppress("ClassName", "PropertyName", "RedundantUnitReturnType", "NestedLambdaShadowedImplicitParameter", "RemoveRedundantQualifierName")
package thrift.test

data class Bonk(
  var message: kotlin.String? = null,
  var type: kotlin.Int? = null
) : org.apache.thrift.TBase<Bonk, Bonk._Fields> {
  enum class _Fields(private val thriftFieldId: kotlin.Short, private val fieldName: kotlin.String) : org.apache.thrift.TFieldIdEnum {
    MESSAGE(1, "message"),
    TYPE(2, "type");

    override fun getThriftFieldId() = thriftFieldId

    override fun getFieldName() = fieldName

    companion object {
      @kotlin.jvm.JvmStatic
      fun findByValue(value: kotlin.Int): _Fields? {
        return when (value) {
          1 -> MESSAGE
          2 -> TYPE
          else -> null
        }
      }

      @kotlin.jvm.JvmStatic
      fun findByName(name: kotlin.String): _Fields? {
        return when (name) {
          "message" -> MESSAGE
          "type" -> TYPE
          else -> null
        }
      }
    }
  }

  companion object {
    private val STRUCT_DESC: org.apache.thrift.protocol.TStruct = org.apache.thrift.protocol.TStruct("Bonk")
    private val MESSAGE_FIELD_DESC: org.apache.thrift.protocol.TField = org.apache.thrift.protocol.TField("message", org.apache.thrift.protocol.TType.STRING, 1)
    private val MESSAGE_FIELD_META_DATA: org.apache.thrift.meta_data.FieldMetaData = org.apache.thrift.meta_data.FieldMetaData(
      "message",
      org.apache.thrift.TFieldRequirementType.DEFAULT,
      org.apache.thrift.meta_data.FieldValueMetaData(org.apache.thrift.protocol.TType.STRING))
    private val TYPE_FIELD_DESC: org.apache.thrift.protocol.TField = org.apache.thrift.protocol.TField("type", org.apache.thrift.protocol.TType.I32, 2)
    private val TYPE_FIELD_META_DATA: org.apache.thrift.meta_data.FieldMetaData = org.apache.thrift.meta_data.FieldMetaData(
      "type",
      org.apache.thrift.TFieldRequirementType.DEFAULT,
      org.apache.thrift.meta_data.FieldValueMetaData(org.apache.thrift.protocol.TType.I32))
    private val metadata: Map<_Fields, org.apache.thrift.meta_data.FieldMetaData> = mapOf(
      _Fields.MESSAGE to MESSAGE_FIELD_META_DATA,
      _Fields.TYPE to TYPE_FIELD_META_DATA,
    )
    init {
      org.apache.thrift.meta_data.FieldMetaData.addStructMetaDataMap(Bonk::class.java, metadata)
    }
  }

  private object BonkStandardScheme : org.apache.thrift.scheme.StandardScheme<Bonk>() {
    override fun read(iproto: org.apache.thrift.protocol.TProtocol, struct: Bonk) {
      iproto.apply {
        readStruct {
          var stopped = false
          while (!stopped) {
            stopped = readField {
              val skipNext = { org.apache.thrift.protocol.TProtocolUtil.skip(iproto, type) }
              when (id.toInt()) {
                1 -> {
                  if (type == org.apache.thrift.protocol.TType.STRING) {
                    struct.message = readString()
                  } else {
                    skipNext()
                  }
                }
                2 -> {
                  if (type == org.apache.thrift.protocol.TType.I32) {
                    struct.type = readI32()
                  } else {
                    skipNext()
                  }
                }
                else -> skipNext()
              }
            }
          }
          struct.validate()
        }
      }
    }

    override fun write(oproto: org.apache.thrift.protocol.TProtocol, struct: Bonk) {
      struct.validate()
      oproto.apply {
        writeStruct(STRUCT_DESC) {
          struct.message?.let {
            writeField(MESSAGE_FIELD_DESC) {
              writeString(it)
            }
          }
          struct.type?.let {
            writeField(TYPE_FIELD_DESC) {
              writeI32(it)
            }
          }
          writeFieldStop()
        }
      }
    }

  }

  override fun compareTo(other: Bonk?): kotlin.Int {
    val comparator = compareBy<Bonk> { it::class.java.name }
      .thenBy { it.message } 
      .thenBy { it.type } 
    return nullsFirst(comparator).compare(this, other)
  }

  override fun fieldForId(fieldId: kotlin.Int): _Fields {
    return _Fields.findByValue(fieldId) ?: throw kotlin.IllegalArgumentException("invalid fieldId $fieldId")
  }

  override fun getFieldValue(field: _Fields): kotlin.Any? {
    return when (field) {
      _Fields.MESSAGE -> this.message
      _Fields.TYPE -> this.type
    }
  }

  @Suppress("UNCHECKED_CAST")
  override fun setFieldValue(field: _Fields, value: kotlin.Any?): kotlin.Unit {
    when (field) {
      _Fields.MESSAGE -> this.message = value as kotlin.String?
      _Fields.TYPE -> this.type = value as kotlin.Int?
    }
  }

  override fun isSet(field: _Fields): kotlin.Boolean {
    return when (field) {
      _Fields.MESSAGE -> this.message != null
      _Fields.TYPE -> this.type != null
    }
  }

  override fun deepCopy(): Bonk {
    return Bonk (
      message,
      type,
    )
  }

  override fun clear(): kotlin.Unit {
    message = null
    type = null
  }

  @kotlin.jvm.Throws(org.apache.thrift.TException::class)
  fun validate(): kotlin.Unit {
  }

  override fun read(iproto: org.apache.thrift.protocol.TProtocol): kotlin.Unit {
    require(org.apache.thrift.scheme.StandardScheme::class.java == iproto.scheme) { "only standard scheme is supported for now" }
    BonkStandardScheme.read(iproto, this)
  }

  override fun write(oproto: org.apache.thrift.protocol.TProtocol): kotlin.Unit {
    require(org.apache.thrift.scheme.StandardScheme::class.java == oproto.scheme) { "only standard scheme is supported for now" }
    BonkStandardScheme.write(oproto, this)
  }

}

[jimexist]

had to rebase to pickup fix from #2585