Protobuf

A format, recognised by .proto sources: the schemas, and the gRPC services they define. buf.yaml is YAML, the Data format's, and holds buf's settings. A CI job works with the ecosystem when it runs buf, protoc (or python -m grpc_tools.protoc), or the bufbuild/buf-action and bufbuild/buf-setup-action actions.

schema-validation

The schemas compile: buf build (or bufbuild/buf-action, which builds first), or protoc on the files.

static-analysis

buf lint, with the STANDARD rules by default and the project's in buf.yaml's lint section.

code-formatting

buf format --diff --exit-code, which fails on a file it would change (--diff alone only prints the change); buf format -w rewrites the files. bufbuild/buf-action formats unless format: false.

schema-declared

Every .proto file declares its syntax (proto3; or its edition), without which protoc reads it as proto2 with a warning, and its package, without which its messages are in the global namespace (buf's PACKAGE_DEFINED rule).

schema-compatibility

buf breaking against the main branch (--against .git#branch=main) or the registry; bufbuild/buf-action runs it unless breaking: false. Warns when CI checks nothing.

Not judged

buf.lock beside a buf.yaml with deps is a dependency rule (#24). The generated code is the generating language's. The other checks have no tool for schemas and are skipped.