build(deps): bump github.com/golang/protobuf from 1.3.1 to 1.4.0

[dependabot-preview]

Bumps github.com/golang/protobuf from 1.3.1 to 1.4.0.

Release notes

Sourced from github.com/golang/protobuf's releases.

v1.4.0

• Overview
  • Backwards compatibility
• Notable changes
  • Wire serialization
  • JSON and text serialization
  • Well-known types
  • Types registry
  • Nil values
  • Errors
  • Generated code
• Upcoming breakage changes
  • Deprecation of Descriptor methods
  • Removal of generator package

Overview

This release of the github.com/golang/protobuf module introduces a number of significant changes relative to the previous minor release. In particular, this module is now implemented in terms of the new google.golang.org/protobuf module, which is the next major revision of Go bindings for protocol buffers. From this point onwards, most of the development effort for Go protobufs will be dedicated to the new module, with minimal changes being made to this module.

See the release notes for the new module for specific implementation details that may affect this release.

Backwards compatibility

This release maintains backwards compatibility with previous releases of this module. Any observable changes in behavior are to fix bugs, change unspecified behavior, or to make behavior more compliant with the protobuf specification. The compatibility document provides us the freedom to make changes in these areas.

Notable changes

Wire serialization

Wire serialization is now implemented in terms of the new proto package by calling out to the relevant functionality in that package (e.g., proto.Marshal and proto.Unmarshal). There should be no observable changes in behavior other what is mentioned elsewhere in the release notes (e.g., behavior around errors or nil values).

JSON and text serialization

The JSON and text format implementations have been ported to use protobuf reflection under the hood instead of relying on Go reflection. This provides flexibility as they can operate on any concrete message type that properly implements the new proto.Message interface.

The implementations do not use the new protojson or prototext packages in order to maintain a higher degree of backwards compatibility. Our analysis unfortunately showed us that too many tests rely on their output being stable by performing byte-for-byte comparisons. Even though the compatibility promise gives us the freedom to change the output, we have chosen not to do so for pragmatic reasons. The implementations are now functionally frozen (bugs and all) and will not receive future improvements. Users are encouraged to migrate to the protojson or prototext packages instead.

Well-known types

The well-known types declared under ptypes are moved to the google.golang.org/protobuf module. The packages continue to exist, but all declarations forward to ones in the new module.

For a period of time, it is expected that the protoc-gen-go plugin continues to generate code with dependencies on the well-known types in this module. The import paths for the well-known types are determined by the go_package option specified in the .proto files. Since these files are managed by the main protocol buffers project, it will require a new release of the protobuf toolchain before the new import paths take effect. Depending on this module’s packages for well-known types is fine since they simply forward over to the new packages.

While descriptor and plugin are not packages for well-known types, they too have also been moved to the new module.

Types registry

In order for dynamic usages of protobufs to operate correctly, there must be a unified registry between this module and the new google.golang.org/protobuf module. The protoregistry package is the primary registry for all protobuf files that are linked into a Go program. The registration functions (e.g., proto.RegisterType) in this package forward to the global registries in that module, and the lookup functions (e.g., proto.MessageType) in this package source from the global registries in that module.

Nil values

... (truncated)

Commits

• 1b794fe all: upgrade to google.golang.org/protobuf@v1.21.0 (#1081)
• e9dc0d7 all: update to wrap google.golang.org/protobuf
• 3a3cefd all: use google.golang.org/protobuf/testing/protopack for tests (#1063)
• c8ad453 all: use google.golang.org/encoding/protowire (#1062)
• 7592abe internal/cmd/generate-alias: fix for lacking go_package options (#1061)
• b860323 proto: inline the implementation of protoimpl.X.ExtensionDescFromType (#1056)
• 8466869 go.mod: set go version to go1.9 (#1055)
• 7bd8073 proto: use fixed UnmarshalState API
• 3f90b72 all: use google.golang.org/protobuf v1.20.0
• a3619c1 all: use new protogen options API
• Additional commits viewable in compare view

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[dependabot-preview]

Superseded by #16.