APIv2: track breaking changes

[dsnet]

This is a meta-issue for tracking any breaking changes that occur before the final v2 release. Since v2 is not yet released, we reserve the right to make breaking changes to improve the API to be as good as it can be.

The CL (changelist) that introduces a breaking change will be posted here as a comment. Subscribe to this issue to be notified of breakages. We try to batch multiple breaking changes close together in time to reduce user churn.

[dsnet]

Breaking changes:

• CL/182537: reflect/protoregistry: remove Files.RangeFilesByPath method
• CL/175987: reflect/protoreflect: remove bool output for Descriptor.Parent method
• CL/176942: reflect/protoreflect: remove FieldDescriptor.{Oneof,Extendee} methods
• CL/174938: reflect/protoreflect: remove {Enum,Message}.Type methods
• CL/182597: reflect/protoreflect: remove KnownFields and UnknownFields interfaces

[dsnet]

Minor change:

• CL/182638: reflect/protodesc: use Resolver interface

[neild]

Exceedingly minor change:

• CL/182980: encoding/proto{json,text}.MarshalOptions.Resolver must also resolve extensions

[dsnet]

Minor change:

• CL/183101: internal/fileinit: remove package

This only affects generated code; the fix is to regenerate the .pb.go files.

[dsnet]

Breaking change:

• CL/183700: reflect/protoregistry: remove Files.Find{Enum,Message,Extension,Service}ByName

[neild]

Breaking change:

• CL/183678: all: remove protoreflect.Message.Len

[dsnet]

Behavior change:

• CL/184837: reflect/protodesc: enforce strict validation

This CL enforces that the input file descriptors are well-formed according to the same rules as the C++ protoc implementation.

[neild]

• CL/187857: reflect/prototype: drop Extension

The rest of the prototype package will probably follow soon.

[dsnet]

• CL/189198: compiler/protogen, cmd/protoc-gen-go: use alternative comments API

[neild]

Breaking changes:

• CL/189199: all: refactor extensions, add proto.GetExtension etc.

This CL changes the protoreflect.{Message,Enum,Extension}Type types to no longer implement the corresponding Descriptor interface. (They still have a has-a relationship with the descriptor.)

Accessing extension fields in a protoreflect.Message now requires a protoreflect.ExtensionTypeDescriptor (which implements FieldDescriptor) instead of an ExtensionType (which doesn't any more). ExtensionType.Descriptor returns an ExtensionTypeDescriptor.

• CL/189340: all: drop reflect/prototype package

The prototype package is removed as unnecessary.

[neild]

Breaking change:

• CL/189563: all: unify protoV1.ExtensionDesc and proto.ExtensionType
• CL/189564: internal/impl: clean up obsolete ExtensionInfo fields/funcs

The protoiface.ExtensionDescV1 type is removed. (And lots of other internal refactoring, but I believe that's the only breaking API change.) This is unlikely to affect anyone.

[dsnet]

Minor breaking change:

• CL/191039: compiler/protogen: export Plugin.FilesByPath

[neild]

Breaking change:

• CL/192139: rename ExtensionType Descriptor method to TypeDescriptor

This is a fiddly change, but improves clarity a bit around the very subtle interactions between the various views of an extension.

[neild]

Breaking change:

• CL/193598: remove NewMessage methods

Superseded by the more general-purpose Message.NewField, List.NewElement, and Map.NewValue.

[neild]

Breaking change:

• CL/199060: remove {Enum,Message,Extension}Type.GoType methods

Removed to simplify the interface, and because there are now better ways to do just about everything they were used for.

[neild]

Minor breaking change:

• CL/204897: remove nullability from repeated extension fields

m.Has(extensionTypeDescriptor) will now return false for a zero-length repeated extension field.

[neild]

Breaking change:

• CL/206017: remove deprecated APIs

The (*Files).Register and (*Types).Register functions in the protoregistry package have been replaced by type-safe Register{File,Enum,Message,Extension} methods.

The protoregistry.NewFiles and protoregistry.NewTypes functions are gone. (Just call Register...)

The protoregistry.Type type is removed (nothing references it any more).

[dsnet]

Minor breaking change:

• CL/207077: testing/protocmp: switch Enum.Number to be a method

[neild]

• CL/209018: reflect/protoreflect: add {Message,List,Map}.IsValid
• CL/209019: all: fix reflection behavior for empty lists and maps

Minor addition to some protoreflect types, only affecting implementations of those types.

Brought reflection behavior for empty lists and maps in line with documentation. Technically not a breaking change (just doing what the documentation said!), but it would have been easy to depend on the previous behavior by accident.

[neild]

• CL/215718: all: add ProtoMethods method to protoreflect.Message
• CL/215719: all: abstract fast-path marshal and unmarshal inputs and outputs

Changes to the fast-path ProtoUnmarshal method: It moves into the protoreflect.Message interface, and the method signature changes a bit.

Performance improvement (avoids an interface->interface type conversion, which is expensive) and future-proofing.

[neild]

• CL/219145: proto: remove shallow merge support, and MergeOptions

Shallow merges were well-defined, but we're debating whether that definition is useful. Dropped support for shallow merges for now, since this isn't a v1 feature we need to preserve.

[neild]

• CL/220117: reflect/protoreflect: add List.AppendMutable and Map.Mutable

Convenience methods on protoreflect's List and Map types.

[neild]

• CL/219505: all: fast-path method refactoring

One last change to the fast-path method signatures, for consistency and future expansion.

[neild]

APIv2 is released. No more breaking changes!