The repo contains a a cli that uses tonic-build to generate rust-code from protobuf-files.
tonic-build already does this, the cli is a front-end to
that with some added code to make sure that the generated files are placed in a valid path, and takes care of the
module structuring.
prost-build used to ship with cmake which we would like to avoid.
cmake was used to build protoc which was then used for the proto-to-rust codegen.
The final decision from the prost maintainers side is that the user should provide their own protoc and check in the code
instead of building it in a build.rs, to make that process simpler, this cli was created.
Uses a local version of protoc on path to generate rust code form a workspace specification passed to the CLI. The CLI can also be used to validate generated Rust code against source protocol files, for example, in CI.
There are quite a few problems with this tool, for now it remains the best alternative for our Protobuf pipeline, some things to take into account follows.
Running this tool requires at minimum protoc to be installed on the user's machine,
many protocol buffers found in the wild have dependencies in the form of other .proto files. Which also
have to be sourced.
Many .proto files that you might want to build have dependencies on the google.protobuf
types,
many .proto authors assume that these are available to the user, which may or may not be true.
There has been discussions about vendoring them here since they are so common but for now no vendoring will be done, since they are not mandatory in many cases.
A middle-ground is to vendor the dependency protos yourself, and run this tool with the directory where you placed those
.proto files specified (-d my-dep-dir).
On tonic minor versions sometimes comments or other non-functional changes are made, these will cause the
validate command to reject old protos generated by a lower version of this tool, requiring regeneration.
It could be argued that therefore a minor version change in tonic becomes a major version change
for this tool, although that may be a bit philosophical since the generated code runs the same.
Tonic converts protobuf comments to doc comments, if these include code examples, cargo will attempt to execute them
when running cargo test (doc-test stage).
This behaviour is different form using tonic-build, since those doc-comments are generated where cargo doesn't try
to run them.
Running them is almost always guaranteed to fail in the best case (because they will be non-rust code or not code at all),
and be a lurking security vulnerability in the worst case where someone have inserted malicious Rust-code in a doc-comment.
Ideally it'd be easier to disable running doc-test on a per-module basis. Placing generated protos in a separate lib which doesn't run doc-comments is a safer choice, although doc-tests being opt-in would be significantly safer.
Generate types from a .proto into an project.
cargo r -r -p proto-gen -- generate -d examples/example-project/proto -f examples/example-project/proto/my-proto.proto -o examples/example-project/src/proto_typesThis will generate Rust code from the proto specified in examples/example-project/proto/my-proto.proto and place it
in examples/example-project/src/proto_types.
cargo r -r -p proto-gen -- validate -d examples/example-project/proto -f examples/example-project/proto/my-proto.proto -o examples/example-project/src/proto_typesThis will also generate Rust code (to a temporary directory) and the run a diff against the code contained in examples/example-project/src/proto_types.
If it finds any diffs it will exit with error code 1 and a message.
If we want to use includes, the directory to include needs to be specified.
cargo r -r -p proto-gen -- generate -d examples/example-project/dep_protos -d examples/example-project/proto_with_deps -f examples/example-project/proto_with_deps/my-proto.proto -o examples/example-project/src/proto_typesHere we're passing -d twice, once to include the dependency protos, and one to include the protos we want to generate.
cargo r -r -p proto-gen -- validate -d examples/example-project/dep_protos -d examples/example-project/proto_with_deps -f examples/example-project/proto_with_deps/my-proto.proto -o examples/example-project/src/proto_types
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