feat(relations): coerce bare cross-family DAG dependency refs (item 92) - #284
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A DAG target anchored on family X that joins a BARE foreign-family dependency ref now compiles the ref in its own family and coerces the result to the anchor's family via _coerce_to_match (item 94), instead of leaving the ref on the anchor pair to fail in read(). - _anchor_prototype(family, dialect) + _is_lazy_narwhals helpers - _resolve_identity_leaf(name) -> (family, dialect, ReadRelNode) - foreign branch: bare ReadRelNode -> compile own family + coerce; derived root stays on the anchor pair (item 97's territory) - upfront lazy-narwhals-anchor guard (order-independent rejection) Design: mountainash-central 2026-08-14-dag-cross-family-bare-dependency-coercion.md (Rev 5)
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Implements backlog item 92 — RelationDAG cross-family bare-dependency coercion.
A DAG target anchored on one family that joins a BARE foreign-family dependency ref now compiles the ref in its own family and coerces the result to the anchor's family via
_coerce_to_match(item 94), instead of leaving the ref on the anchor pair to fail raw inread().Changes
_anchor_prototype(family, dialect)+_is_lazy_narwhalsmodule helpers_resolve_identity_leaf(name)→(family, dialect, ReadRelNode)ReadRelNoderoot → compile own family + coerce + restore; derived root stays on the anchor pair (item 97's territory)Tests:
tests/relations/dag/test_dag_cross_family_bare.py(acceptance + Ibis/narwhals-anchor matrix + derived-non-rescue boundary); updatedTestExplicitBackendPerRefNeverBuildsInvalidHybridto the new own-family-compile semantics.Full suite: 22250 passed, 0 failed. Ruff clean. (mypy baseline has pre-existing
import-untyped/capability_census errors, unchanged.)Design: mountainash-central
2026-08-14-dag-cross-family-bare-dependency-coercion.md(Revision 5).