- Rename _BACKENDS → _backends: pyright treats uppercase module-level
names as constants and flags the reassignment in _get_backends() as
reportConstantRedefinition; lowercase avoids this.
- Add TYPE_CHECKING guard importing CommitCancelled/Freezer/get_freezer
from .freeze: pyright cannot see module-level __getattr__ bindings, so
reportUnsupportedDunderAll fired for those three __all__ entries; the
guard makes them visible to the type checker without running at import
time.
- Update test_backend_selection.py to patch _backends (lowercase).
`undefined-all-variable` fires on CommitCancelled / Freezer / get_freezer
in __all__ because pylint can't see module-level __getattr__ bindings;
`global-statement` fires on the _BACKENDS singleton setter. Both are
intentional patterns — add inline disables rather than suppress globally.
Importing backend.docker.util previously triggered eager loading of all
three backend packages (~76 modules) because backend/__init__.py imported
DockerBottleBackend, FirecrackerBottleBackend, and MacosContainerBottleBackend
at module scope. This made the module prohibitively expensive to import
from the orchestrator layer and elsewhere.
The three backend imports are now deferred into _get_backends(), which
loads all three on first call and caches the result in the module-level
_BACKENDS variable (initially None). Module-level __getattr__ exposes
backend classes and freeze symbols lazily for existing import/patch sites.
backend/docker/util.py raw subprocess.run(["docker", ...]) calls are
replaced with the shared run_docker primitive from docker_cmd, eliminating
the duplication between the backend and orchestrator implementations.
_silent_run() is removed; image_exists() is inlined directly onto
run_docker. The commit_container test is updated to patch run_docker
instead of subprocess.run.
didericis-claude