Nest-Multer-Bug

A repo that illustrates a potential bug in NestJS

Setup

git clone git@github.com:Haltarys/Nest-Multer-Bug.git
npm i
npm run start:dev

To upload a file, run (in another terminal):

curl localhost:3000/image/upload -F "file=@./nest-cli.json"

Description of the bug

When uploading a file to the application (launched with npm run start:dev), after a few seconds, the app reloads as if a change to a source file ocurred and gets stuck at File change detected. Starting incremental compilation.... This happens even if the file is saved in a directory that is not in src.

Details

This example is based on the documentation on how to upload a file. In order to save a file to the disk you need to add the following lines of code to the imports of the AppModule.

MulterModule.register({
  dest: './upload',
});

Note that ./upload is relative to the root directory, not src.

Extract from app.module.ts:

@Module({
  imports: [
    MulterModule.register({
      dest: './upload',
    }),
    ImageModule,
  ],
  controllers: [AppController],
  providers: [AppService],
})

However, if this code is added to a sub-module of AppModule (namely ImageModule), the auto-reload triggers every time a file is uploaded to the endpoint.

The file is uploaded and saved regardless of the method used.

The auto-reload does not trigger with a simple POST request:

curl localhost:3000/image/upload -X POST