### New properties in an existing class

When adding a property to an existing class (task, extension, domain object, etc), the API should consist of managed lazy properties.  However, some exceptions need to be made to keep backwards compatibility with existing builds.

This is preferred when the implementation type is internal:

```groovy
public interface ExistingThing {
    String getOtherProperty()
    void setOtherProperty(String s)

---
jjbb-template: matrix-gradle-unix.yml
vars:
  - job-name: elastic+elasticsearch+%BRANCH%+periodic+bwc
  - job-display-name: "elastic / elasticsearch # %BRANCH% - backwards compatibility matrix"
  - job-description: "Testing of the Elasticsearch %BRANCH% branch backwards compatibility matrix.\n"
  - matrix-yaml-file: ".ci/bwcVersions"
  - matrix-variable: BWC_VERSION

.vscode/

# vs stuff
.vs/

# testing stuff
**/.local*
.vagrant/
/logs/

# osx stuff
.DS_Store

# default folders in which the create_bwc_index.py expects to find old es versions in
/backwards
/dev-tools/backwards

# needed in case docs build is run...maybe we can configure doc build to generate files under build?
html_docs

# random old stuff that we should look at the necessity of...
/tmp/
eclipse-build

jjbb-template: generic-gradle-unix.yml
vars:
  - job-name: elastic+elasticsearch+%BRANCH%+intake+multijob+bwc
  - job-display-name: "elastic / elasticsearch # %BRANCH% - intake bwc"
  - job-description: Elasticsearch %BRANCH% branch intake backwards compatibility checks.

   * JUnit test case you are running under. To avoid failing in the face of an exception regardless
   * of JUnit version, implement a {@link SloppyTearDown} instead.
   *
   * <p>tl4j details: For backwards compatibility, {@code junit3.TearDownTestCase} currently does
   * not fail a test when an exception is thrown from one of its {@link TearDown} instances, but
   * this is subject to change. Also, {@code junit4.TearDownTestCase} will.

	MOVQ M0, 8(SP) // 0f7f442408
	MOVQ 8(SP), M0 // 0f6f442408
	MOVQ M0, (AX)  // 0f7f00
	MOVQ M0, (BX)  // 0f7f03
	// On non-64bit arch, Go asm allowed uint32 offsets instead of int32.
	// These tests check that property for backwards-compatibility.
	MOVL 2147483648(AX), AX  // 8b8000000080
	MOVL -2147483648(AX), AX // 8b8000000080
	ADDL 2147483648(AX), AX  // 038000000080
	ADDL -2147483648(AX), AX // 038000000080

  if (project.bwc_tests_enabled) {
    dependsOn tasks.matching { task -> BuildParams.bwcVersions.unreleased.any { version -> bwcTaskName(version) == task.name } }
  }
}

tasks.register("bwcTest") {
  description = 'Runs backwards compatibility tests.'
  group = 'verification'

  if (project.bwc_tests_enabled) {
    dependsOn tasks.matching { it.name ==~ /v[0-9\.]+#bwcTest/ }
  }
}

tasks.withType(Test).configureEach {

  }

  /**
   * Either writes this request to [sink] or measures its content length. We have one method
   * do double-duty to make sure the counting and content are consistent, particularly when it comes
   * to awkward operations like measuring the encoded length of header strings, or the
   * length-in-digits of an encoded integer.
   */
  private fun writeOrCountBytes(
    sink: BufferedSink?,
    countBytes: Boolean,
  ): Long {

 * under the License.
 */
package org.apache.maven.toolchain.java;

import org.apache.maven.toolchain.model.ToolchainModel;
import org.slf4j.Logger;

/**
 * Provides backwards compatibility with Maven 3.2.3 and earlier. Clients that do not require compatibility with Maven
 * 3.2.3 and earlier are encouraged to use {@link JavaToolchainImpl}.

export FESS_VAR_PATH
export FESS_DICTIONARY_PATH
export FESS_HEAP_SIZE
export SEARCH_ENGINE_HOME
export SEARCH_ENGINE_HTTP_URL
export FESS_JAVA_OPTS
export JAVA_HOME

lockfile=/var/lock/subsys/$prog

# backwards compatibility for old config sysconfig files, pre 0.90.1
if [ -n $USER ] && [ -z $FESS_USER ] ; then 
   FESS_USER=$USER
fi

checkJava() {
    if [ -x "$JAVA_HOME/bin/java" ]; then
        JAVA="$JAVA_HOME/bin/java"