Unused code generated with ts-proto and nestJs=true when using google.protobuf.Struct

[00KL]

Problem description

When generating TypeScript code from a .proto file that uses google.protobuf.Struct and the option ts_proto_opt=nestjs=true, the generated code includes unused functions and interfaces.
This unused code causes TypeScript type-checking errors in NestJS projects when the following options are enabled in tsconfig.json:

"noUnusedLocals": true,
"noUnusedParameters": true

With these options, TypeScript will report errors for unused code, such as:

ERROR in ./libs/device-communication/src/generated/google/protobuf/struct.ts:104:10
TS6133: 'createBaseValue' is declared but its value is never read.
    102 | };
    103 |
  > 104 | function createBaseValue(): Value {
        |          ^^^^^^^^^^^^^^^
    105 |   return {};
    106 | }
    107 |

ERROR in ./libs/device-communication/src/generated/google/protobuf/struct.ts:195:28
TS6133: 'T' is declared but its value is never read.
    193 | } as any;
    194 |
  > 195 | export interface MessageFns<T> {}
        |                            ^^^
    196 |
    197 | export interface StructWrapperFns {
    198 |   wrap(object: { [key: string]: any } | undefined): Struct;

Found 2 errors in 5260 ms.

Reproduction steps

1. Create a new empty folder and enter it:

   mkdir grpc-node-unused-code-example
   cd grpc-node-unused-code-example

2. Create a file named package.json with the following content:

   {
     "name": "grpc-node-unused-code-example",
     "version": "1.0.0",
     "private": true,
     "description": "Minimal reproduction for unused code generated by ts-proto with nestJs=true and google.protobuf.Struct",
     "scripts": {
       "generate": "protoc --plugin=./node_modules/.bin/protoc-gen-ts_proto --ts_proto_out=./generated --ts_proto_opt=nestJs=true,unrecognizedEnum=false,env=node -I=. example.proto"
     },
     "devDependencies": {
       "ts-proto": "^2.7.2",
       "typescript": "^5.8.3"
     }
   }

3. Install the dependencies:

   npm install

4. Create a file named example.proto with the following content:

   syntax = "proto3";
   import "google/protobuf/struct.proto";
   
   service ExampleService {
     rpc ExampleMethod (google.protobuf.Struct) returns (google.protobuf.Struct);
   }

5. Create a file named tsconfig.json with the following content:

   {
     "compilerOptions": {
       "noUnusedLocals": true,
       "noUnusedParameters": true
     }
   }

6. Run the code generation command (either as a script or raw command):

   • Using npm script:

     npm run generate

   • Or directly:

     npx protoc --plugin=./node_modules/.bin/protoc-gen-ts_proto --ts_proto_out=./generated --ts_proto_opt=nestJs=true,unrecognizedEnum=false,env=node -I=. example.proto

7. Check the generated TypeScript code for google.protobuf.Struct in the generated directory.

You will see code like:

function createBaseValue(): Value {
  return {};
}

export interface MessageFns<T> {}

These code snippets are never used.

Environment

• OS name, version and architecture:
• Node version:
• Node installation method:
• Compiler version:
• Package name and version:
  • ts-proto@2.7.2
  • typescript@5.8.3

Additional context

This only happens when using ts_proto_opt=nestjs=true and the noUnusedLocals/noUnusedParameters options.
Include logs or more context if needed.

[stephenh]

Hi @00KL ; historically ts-proto tries very hard to not generated unused code, so I sympathesize that this is annoying; it looks like this check is tripping us up:

https://github.com/stephenh/ts-proto/blob/main/src/main.ts#L197

Because it leads to this line getting called:

https://github.com/stephenh/ts-proto/blob/main/src/main.ts#L223

Which I guess we don't need for NestJS output & specifically the struct output?

Dunno, I don't have time to look into the nuances, but if you'd like to poke around there & submit a PR, that would be great! Thanks!