Upgrade protoc and protoc-gen-go-grpc versions to matching terraform-plugin-go

[SarahFrench]

Do we want these values to match terraform-plugin-go? Does it even matter?

Not sure, but it's still good to keep these dependencies updated, and updating to match terraform-plugin-go feels like a good thing to arbitrarily aim for right now.

This PR:

• Updates the version of protoc we use
• Updates the version of protoc-gen-go-grpc we use
• Update the code generator in internal/rpcapi/dynrpcserver/generator/main.go to be able to handle the generic types that are now in use after the update.
  • This is due to this commit grpc/grpc-go@bb9882e that was added in https://github.com/grpc/grpc-go/releases/tag/cmd/protoc-gen-go-grpc/v1.4.0 as experimental and was swapped to on-as-default in https://github.com/grpc/grpc-go/releases/tag/cmd/protoc-gen-go-grpc/v1.5.0
  • This PR upgrades to v1.5.1, so we pull in those changes

A lot of diffs in this PR are in generated code, so I've highlighted areas where manual changes were made with comments. See also diffs in internal/rpcapi/dynrpcserver/generator/main.go and go.mod/sum

Target Release

N/A

Rollback Plan

• If a change needs to be reverted, we will roll out an update to the code within 7 days.

Changes to Security Controls

Are there any changes to security controls (access controls, encryption, logging) in this pull request? If so, explain.

CHANGELOG entry

• This change is user-facing and I added a changelog entry.
• This change is not user-facing.

[SarahFrench]

Keeping this in draft until after HashiConf

[SarahFrench]

In the Code Consistency Checks GHA make generate is failing with:

>2025/10/08 13:22:23 don't know what to do with parameter type google.golang.org/grpc.ServerStreamingServer[github.com/hashicorp/terraform/internal/rpcapi/terraform1/dependencies.BuildProviderPluginCache_Event]

Which is due to hitting this code. When I run the generator script locally I don't see any generic types being passed in 🤔

Edit: deleting the contents of tools/protobuf-compile/.workdir allowed me to reproduce the problem. Maybe the dependency updates weren't reflected in the binaries in that folder?

[SarahFrench]

This file has manually-made diffs that need closer review

[SarahFrench]

Here's generated code that informed this change:

terraform/internal/cloudplugin/cloudproto1/cloudproto1_grpc.pb.go

Lines 63 to 64 in 6c41e77

	// This type alias is provided for backwards compatibility with existing code that references the prior non-generic stream type by name.
	type CommandService_ExecuteClient = grpc.ServerStreamingClient[CommandResponse]

[SarahFrench]

This file has diffs that need closer review

[SarahFrench]

Here's generated code that informed this change:

terraform/internal/tfplugin5/tfplugin5_grpc.pb.go

Lines 1276 to 1277 in 6c41e77

	// This type alias is provided for backwards compatibility with existing code that references the prior non-generic stream type by name.
	type Provisioner_ProvisionResourceClient = grpc.ServerStreamingClient[ProvisionResource_Response]

[SarahFrench]

This file has manually-made diffs that need closer review

[SarahFrench]

Here's generated code that informed this change:

terraform/internal/tfplugin6/tfplugin6_grpc.pb.go

Lines 443 to 444 in 6c41e77

	// This type alias is provided for backwards compatibility with existing code that references the prior non-generic stream type by name.
	type Provider_ReadStateBytesClient = grpc.ServerStreamingClient[ReadStateBytes_Response]

[SarahFrench]

This file has manually-made diffs that need closer review

[SarahFrench]

Here's generated code that informed this change:

terraform/internal/stacksplugin/stacksproto1/stacksproto1_grpc.pb.go

Lines 63 to 64 in 6c41e77

	// This type alias is provided for backwards compatibility with existing code that references the prior non-generic stream type by name.
	type CommandService_ExecuteClient = grpc.ServerStreamingClient[CommandResponse]

terraform/internal/cloudplugin/cloudproto1/cloudproto1_grpc.pb.go

Lines 63 to 64 in 6c41e77

	// This type alias is provided for backwards compatibility with existing code that references the prior non-generic stream type by name.
	type CommandService_ExecuteClient = grpc.ServerStreamingClient[CommandResponse]

[liamcervante]

I think this looks fine 👍 I guess the mockgen package seems to not be keeping up with the generics used by the proto files but nothing we can do about it.

[SarahFrench]

Thanks Liam! Yeah it'd be nice if the mocks had the correct type baked in, instead of requiring setup in the test code, but if that causes issues in future I guess we can set up more test helpers.

FYI to any readers/future me: I'm planning to merge this to main tomorrow after the release, and I'm not planning to backport. Given that the main branch currently represents the first alpha release of 1.15, and alphas do not need Mend scans, merging this PR doesn't impact anyone's release rota.

[SarahFrench]

Going ahead with merge despite the release not going out; main branch doesn't affect the release code.