src-gen does not preserve directory structure

[tpluscode]

I have mappings in nested dir structure which results in the following, including the generated output

/
├── mappings/
│   ├── dimensions/
│   │   ├── customer.xrm
│   │   └── product.xrm
│   └── facts.xrm
└── src-gen/
    ├── customer.csv.meta.json
    ├── facts.csv.meta.json
    └── product.csv.meta.json

Instead, I expected the directory dimensions to be kept in src-gen:

/
├── mappings/
│   ├── dimensions/
│   │   ├── customer.xrm
│   │   └── product.xrm
│   └── facts.xrm
└── src-gen/
    ├── dimensions/
    │   ├── customer.csv.meta.json
    │   └── product.csv.meta.json
    └── facts.csv.meta.json