What's this for?

protoc-gen-openapi is a plugin for the Google protocol buffer compiler to generate openAPI V3 spec for any given input protobuf. It runs as a protoc-gen- binary that the protobuf compiler infers from the openapi_out flag.

Build protoc-gen-openapi

protoc-gen-openapi is written in Go, so ensure that is installed on your system. You can follow the instructions on the golang website or on Debian or Ubuntu, you can install it from the package manager:

sudo apt-get install -y golang

To build, run the following command from this project directory:

make build

Then ensure the resulting protoc-gen-openapi binary is in your PATH. A recommended location is $HOME/bin:

cp _output/.bin/protoc-gen-openapi $HOME/bin

Since the following is often in your $HOME/.bashrc file:

export PATH=$HOME/bin:$PATH

Using protoc-gen-openapi

---

TIP

The -I option in protoc is useful when you need to specify proto paths for imports.

---

Then to generate the OpenAPI spec of the protobuf defined by file.proto, run

protoc --openapi_out=output_directory input_directory/file.proto

With that input, the output will be written to

output_directory/file.json

Other supported options are:

• per_file
  • when set to true, the output is per proto file instead of per package.
• single_file
  • when set to true, the output is a single file of all the input protos specified.
• use_ref
  • when set to true, the output uses the $ref field in OpenAPI spec to reference other schemas.
• yaml
  • when set to true, the output is in yaml file.
• include_description
  • when set to true, the openapi schema will include descriptions, generated from the proto message comment.
• multiline_description
  • when set to true, the openapi schema will include descriptions, generated from the proto message comment, that can span multiple lines. This can only be used with yaml=true.
• enum_as_int_or_string
  • when set to true, the openapi schema will include x-kubernetes-int-or-string on enums.
• additional_empty_schemas
  • a + separated list of message names (core.solo.io.Status), whose generated schema should be an empty object that accepts all values.
• proto_oneof
  • when set to true, the openapi schema will include oneOf emulating the behavior of proto oneof.
• int_native
  • when set to true, the native openapi schemas will be used for Integer types instead of Solo wrappers that add Kubernetes extension headers to the schema to treat int as strings.
• disable_kube_markers
  • when set to true, kubebuilder markers and validations such as PreserveUnknownFields, MinItems, default, and all CEL rules will be omitted from the OpenAPI schema. The Type and Required markers will be maintained.
• ignored_kube_marker_substrings
  • when set, this list of substrings will be used to identify kubebuilder markers to ignore. When multiple are supplied, this will function as a logical OR i.e. any rule which contains a provided substring will be ignored