Simple plugin to generate an enum object for every oneof

buf.gen.yaml

version: v1
plugins:
  - name: oneofhelper
    path: ./src/protoc-gen-oneofhelper.ts
    opt: target=ts
    out: src/gen

protoc-gen-oneofhelper.ts

#!/usr/bin/env -S npx tsx

import { createEcmaScriptPlugin, runNodeJs } from "@bufbuild/protoplugin";
import { localName, GeneratedFile, Schema } from "@bufbuild/protoplugin/ecmascript";
import type { DescMessage } from "@bufbuild/protobuf";

const protocGenOneofhelper = createEcmaScriptPlugin({
  name: "protoc-gen-oneofhelper",
  version: `v1.0.0`,
  generateTs (schema: Schema) {
    for (const file of schema.files) {
      const f = schema.generateFile(file.name + "_oneofhelper.ts");
      f.preamble(file);
      for (const message of file.messages) {
        generateMessage(f, message);
      }
    }
  }
});

// prettier-ignore
function generateMessage(f: GeneratedFile, message: DescMessage) {
  for (const oo of message.oneofs) {
    // Name of the enum we are about to generate
    const name = localName(oo).replace(/^[a-z]/, v => v.toUpperCase()) + "Case";
    f.print`export const ${name} = {`;
    for (const field of oo.fields) {
      f.print`  ${field.name.toUpperCase()}: '${localName(field)}',`;
    }
    f.print`} as const;`;
  }
  for (const nestedMessage of message.nestedMessages) {
    generateMessage(f, nestedMessage);
  }
}

runNodeJs(protocGenOneofhelper);

posting here to reference everything in on place

Notes:

1. ensure to make file executable by running chmod +x protoc-gen-oneofhelper.ts
2. had to modify the code a bit due to some conflicts with similar named oneof properties
   • This also puts a blank line between enums created

const titleCase = (value: string) => {
  return value.replace(/^[a-z]/, (v) => v.toUpperCase());
};

// prettier-ignore
function generateMessage(f: GeneratedFile, message: DescMessage) {
  for (const oo of message.oneofs) {
    // Name of the enum we are about to generate
    const name = titleCase(message.name) + '_' + titleCase(localName(oo)) + "Case";
    f.print`export const ${name} = {`;
    for (const field of oo.fields) {
      f.print`  ${field.name.toUpperCase()}: '${localName(field)}',`;
    }
    f.print`} as const;
`;
  }
  for (const nestedMessage of message.nestedMessages) {
    generateMessage(f, nestedMessage);
  }
}

Links:

• bufbuild/protobuf-es#337