Data Mapper

Data Mapper keeps in-memory domain objects independent from database schemas and persistence APIs. Mapper implementations translate between the two.

src/app/
├── domain/
├── application/
├── mappers/
└── interface/

Complete Configuration

deply:
  paths: ["."]
  exclude_files:
    - '.*/\.venv/.*'
    - '.*/tests?/.*'
    - '.*/migrations/.*'
  layers:
    - name: domain
      collectors:
        - type: directory
          directories: ["src/app/domain"]
    - name: application
      collectors:
        - type: directory
          directories: ["src/app/application"]
    - name: mappers
      collectors:
        - type: directory
          directories: ["src/app/mappers"]
    - name: interface
      collectors:
        - type: directory
          directories: ["src/app/interface"]
  ruleset:
    domain:
      disallow_layer_dependencies: [application, mappers, interface]
      disallow_external_imports: [django, sqlalchemy, peewee]
    application:
      disallow_layer_dependencies: [mappers, interface]
    interface:
      disallow_layer_dependencies: [domain, mappers]

Mapper interfaces can live in application code, with concrete implementations in mappers. Deply can detect ORM imports in the domain; it cannot verify mapping completeness, identity handling, or transaction behavior.

Validate

deply validate --config=deply.yaml
deply analyze --parallel --config=deply.yaml

Reference: Fowler’s Data Mapper.