Support for protobuf 4

[breun]

I noticed that Spring Initializr sets protoc.version to 3.25.6, while 4.30.2 is the current latest version.

I tried setting protoc.version to 4.30.2 in a demo project, but that results in various compilation errors for the generated source code:

package com.google.protobuf.RuntimeVersion does not exist

cannot find symbol
  symbol:   class RuntimeVersion
  location: package com.google.protobuf

cannot find symbol
  symbol:   method isStringEmpty(java.lang.Object)
  location: class com.google.protobuf.GeneratedMessage

method parseUnknownField in class com.google.protobuf.GeneratedMessage.Builder<BuilderType> cannot be applied to given types;
  required: com.google.protobuf.CodedInputStream,com.google.protobuf.UnknownFieldSet.Builder,com.google.protobuf.ExtensionRegistryLite,int
  found:    com.google.protobuf.CodedInputStream,com.google.protobuf.ExtensionRegistryLite,int
  reason: actual and formal argument lists differ in length

cannot find symbol
  symbol:   method resolveAllFeaturesImmutable()
  location: variable descriptor of type com.google.protobuf.Descriptors.FileDescriptor

Is the the default setup using protoc 3 due to a limitation of the protobuf-maven-plugin that is used?

[dsyer]

Is the the default setup using protoc 3 due to a limitation of the protobuf-maven-plugin that is used?

Don't know. More likely the generator itself is the problem - AFAIK all the plugin does is run protoc. Can you run protoc manually (without the plugin)?

[dsyer]

Actually it works for me. Maybe you forgot to update the grpc-java dependencies? You would need something along the lines of

			<dependency>
				<groupId>com.google.protobuf</groupId>
				<artifactId>protobuf-bom</artifactId>
				<version>${protobuf-java.version}</version>
				<type>pom</type>
				<scope>import</scope>
			</dependency>

[dsyer]

I think we might just bump the versions and do a quick 0.8.0 release

[breun]

Actually it works for me. Maybe you forgot to update the grpc-java dependencies?

I see my property was called protoc.version instead of protobuf-java.version. I may have renamed protobuf-java.version to protoc.version myself, because that is what it seemed to manage, but I see now that protobuf-java.version is also used in spring-grpc-dependencies to managed the protobuf-bom import. But after renaming the property back to protobuf-java.version, I still get a compilation error.

Copying the protobuf-bom import into my project also didn't help, although I also think that shouldn't change anything, because the exact same import is already present in spring-grpc-dependencies?

By the way, when Spring Boot officially adds support for Spring gRPC, is the plan that projects will inherit a default configuration for os-maven-plugin and protobuf-maven-plugin, so they don't need to maintain that themselves? This setup is currently not documented in the Spring gRPC docs, and you only get it when generating a project via Spring Initializr.

Also, there are no releases after 0.5.0 on https://github.com/spring-projects-experimental/spring-grpc/releases, while the docs at https://docs.spring.io/spring-grpc/reference/getting-started.html are for 0.6.0, but 0.7.0 is on Maven Central?

[making]

By the way, Micrometer 1.15 (OTLP Meter Registry) will use protobuf 4 due to the opentelemetry-proto version upgrade.
Zipkin Brave OTLP also uses protobuf 4 for the same reason.
From an ecosystem perspective, I think we will need to support protobuf 4 at some point.
Are there any blockers against raising the default to proto 4?

[dsyer]

That's good intel, thank you. No blockers I am aware of.

[dsyer]

Fixed in 9b8fe44

[dsyer]

Also, there are no releases after 0.5.0 on https://github.com/spring-projects-experimental/spring-grpc/releases, while the docs at https://docs.spring.io/spring-grpc/reference/getting-started.html are for 0.6.0, but 0.7.0 is on Maven Central?

We use Maven Central for release, not github. I can see if I can sync them up, but it's not a high priority. The docs haven't changed.

[breun]

We use Maven Central for release, not github. I can see if I can sync them up, but it's not a high priority.

As a user it's confusing to see some releases there, but not the most recent ones. And since other Spring projects do create GitHub releases, I also expected them here. I understand it's not high priority to have this working, especially since Spring gRPC is currently still an experimental project.

The docs haven't changed.

As a user I don't know this. If I use 0.7.0 I go looking for the docs for 0.7.0, and because I couldn't find them published, I assumed something in the docs publication process was wrong/broken.