cursus.validation.alignment.validators.registry_binding_validator

B3 — Registry-Binding Validator (FZ 31e1d3g3 Phase D, the reframed Level-4).

The old Level-4 step-type validators did SOURCE-LEVEL contract testing — inspect.getsource( builder_class) substring scans + hasattr(builder_class, "_create_estimator") method-presence checks — on the assumption that each step had a hand-written per-step builder whose Python source embodied the contract. Against the shared TemplateStepBuilder shell (all 45 builders are class XStepBuilder(TemplateStepBuilder): STEP_NAME = "X") those checks are meaningless: the source is identical for every step, and hasattr(shell, "_create_estimator") is FALSE because the estimator factory lives in TrainingHandler.make_compute, not the shell — so the old validators report EVERY shell as FAILED (“Missing Training required method: _create_estimator”).

B3 replaces “does the builder SOURCE contain pattern X” with “can the step be REALIZED from its .step.yaml + config” — the genuine residue the construction invariant can’t self-check:

B3-1 HANDLER BINDS — resolve_handler(sagemaker_step_type, patterns.step_assembly) yields a

routable construction handler (raises NoBuilderError for Base/Lambda/unknown). Calling it IS the binding check that replaces the source scan.

B3-2 BUILDER LOADABLE — load_builder_class(step_name) returns a class that is a StepBuilderBase

(the shell or the synthesized declarative shell), i.e. no orphan registry row.

B3-3 CONFIG-FIELD COVERAGE — the resolved config class supplies every field the bound handler +

compute descriptor will read at build time. The required set is the handler’s declared requires_config_fields (DATA — some reads use a runtime attr name, statically undecidable) UNION the descriptor-derived attrs (compute *_field names with non-None values; contract.input_source_overrides values). A field absent from the config class = ERROR; a soft job_arguments[].source provenance attr = WARNING. (Optional config fields that carry a default are NOT requirements — a missing value can’t break getattr.)

class RegistryBindingValidator(workspace_dirs=None)

Bases: object

B3: validate that a step is realizable from its registry row + .step.yaml + config.

Exposes validate_builder_config_alignment(step_name) — the same method name/signature the deleted per-step-type validators exposed — so level_validators.run_level_4_validation and the MCP/CLI consumers are byte-unchanged.

validate_builder_config_alignment(step_name)

Run the three B3 sub-checks. Returns the issue-shaped result the priority resolver reads.