Kotlin’s powerful deprecation features. Most developers should be able to use IntelliJ’s _Code
Cleanup_ for a safe and fast upgrade.


Backwards-Incompatible Changes
------------------------------

#### OkHttpClient final methods

`OkHttpClient` has 26 accessors like `interceptors()` and `writeTimeoutMillis()` that were non-final

 *       returned)
 * </ol>
 *
 * <p>Alas, {@link #reverse} is a little different. As you read backwards through a chain and
 * encounter a call to {@code reverse}, continue working backwards until a result is determined, and
 * then reverse that result.
 *
 * <h3>Additional notes</h3>
 *

        .cipherSuites(*APPROVED_CIPHER_SUITES.toTypedArray())
        .tlsVersions(TlsVersion.TLS_1_3, TlsVersion.TLS_1_2)
        .supportsTlsExtensions(true)
        .build()

    /**
     * A backwards-compatible fallback configuration that works on obsolete client platforms and can
     * connect to obsolete servers. When possible, prefer to upgrade your client platform or server
     * rather than using this configuration.

 *  New: `OkHttpClient.Builder` now has APIs that use `kotlin.time.Duration`.

 *  New: `mockwebserver3.SocketPolicy` is now a sealed interface. This is one of several
    backwards-incompatible API changes that may impact early adopters of this alpha API.

 *  New: `mockwebserver3.Stream` for duplex streams.

 *  New: `mockwebserver3.MockResponseBody` for streamed response bodies.

 *       returned)
 * </ol>
 *
 * <p>Alas, {@link #reverse} is a little different. As you read backwards through a chain and
 * encounter a call to {@code reverse}, continue working backwards until a result is determined, and
 * then reverse that result.
 *
 * <h3>Additional notes</h3>
 *

### 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)

    they could leak passwords and other authentication credentials to insecure
    logs.

 *  **WebSocket API now uses `RequestBody` and `ResponseBody` for messages.**
    This is a backwards-incompatible API change.

 *  **The DNS service is now pluggable.** In some situations this may be useful
    to manually prioritize specific IP addresses.

        return runtimeJdkMetaData.getVendor().getKnownVendor().name() + "/" + vendor.getRawVendor();
    }

    /* Introspect all versions of ES that may be tested against for backwards
     * compatibility. It is *super* important that this logic is the same as the
     * logic in VersionUtils.java. */
    private static BwcVersions resolveBwcVersions(File root) {

                : new NonTerminalImmutableMapEntry<K, V>(key, value, keyBucketHead);
        table[tableIndex] = effectiveEntry;
      } else {
        // We already saw this key, and the first value we saw (going backwards) is the one we are
        // keeping. So we won't touch table[], but we do still want to add the existing entry that
        // we found to entries[] so that we will see this key in the right place when iterating.

---
title: "Go, Backwards Compatibility, and GODEBUG"
layout: article
---

<!--
This document is kept in the Go repo, not x/website,
because it documents the full list of known GODEBUG settings,
which are tied to a specific release.
-->

## Introduction {#intro}

Go's emphasis on backwards compatibility is one of its key strengths.
There are, however, times when we cannot maintain complete compatibility.