Protocol Compiler

• Fix the generated source information for reserved values in Enums.

C++

• Fix -Wunused-parameter in map<string, int> fields (fixes #8494) (#8500)
• Use byteswap.h when building against musl libc (#8503)
• Fix -Wundefined-inline error when using SharedCtor() or SharedDtor() (#8532)
• Fix bug where Descriptor::DebugString() printed proto3 synthetic oneofs.
• Provide stable versions of SortAndUnique().
• Make sure to cache proto3 optional message fields when they are cleared.
• Expose UnsafeArena methods to Reflection.
• Use std::string::empty() rather than std::string::size() > 0.

Kotlin

• Introduce support for Kotlin protos (#8272)
• Restrict extension setter and getter operators to non-nullable T.

Java

• updating GSON and Guava to more recent versions (#8524)
• Reduce the time spent evaluating isExtensionNumber by storing the extension
  ranges in a TreeMap for faster queries. This is particularly relevant for
  protos which define a large number of extension ranges, for example when
  each tag is defined as an extension.
• Fix java bytecode estimation logic for optional fields.
• Optimize Descriptor.isExtensionNumber.

Python

• Add MethodDescriptor.CopyToProto() (#8327)
• Remove unused python_protobuf.{cc,h} (#8513)
• Start publishing python aarch64 manylinux wheels normally (#8530)
• Fix constness issue detected by MSVC standard conforming mode (#8568)
• Make JSON parsing match C++ and Java when multiple fields from the same
  oneof are present and all but one is null.

Ruby

• Add support for proto3 json_name in compiler and field definitions (#8356)
• Fixed memory leak of Ruby arena objects. (#8461)
• Fix source gem compilation (#8471)
• Fix various exceptions in Ruby on 64-bit Windows (#8563)
• Fix crash when calculating Message hash values on 64-bit Windows (#8565)

Conformance Tests

• Added a conformance test for the case of multiple fields from the same
  oneof.

Other

• Use a newer version of rules_proto, with the new rule proto_descriptor_set (#8469)