Promote remaining duck-typed attribute probes (add_chg_spin_ebd, geo_compress, reinit_exclude) to base-class interfaces #5897

Follow-up to the capability-method cleanups on the DPA4 graph branch (supports_native_spin/supports_charge_spin, the uses_graph_lower cluster, and has_spin are now declared on the shared base classes with concrete defaults and probed via direct calls).

Call sites use getattr(obj, "attr", <default>) / hasattr duck typing instead of an interface declared once on the owning base class (make_base_descriptor / make_base_fitting / make_base_model / BaseAtomicModel). Each entry below is a candidate for a concrete-default method on its base, so a typo'd or renamed name raises instead of silently degrading to the default.

Inventory

(Updated after a receiver-agnostic re-sweep of both getattr and hasattr over all of deepmd/ outside the frozen deepmd/pt tree — the original issue text understated the scope.)

Charge-spin interface family (largest cluster, ~25 sites)

• has_chg_spin_ebd — 5 hasattr sites; get_dim_chg_spin — 10 hasattr sites; has_default_chg_spin — 5; get_default_chg_spin — 3; add_chg_spin_ebd attribute — dpmodel/atomic_model/dp_atomic_model.py, pt_expt/infer/deep_eval.py (2 sites). Candidate: declare the whole family on the owning bases (atomic model and/or descriptor) with concrete defaults (False/0/None) and drop every probe.

Compression / kernel-eligibility attributes

• geo_compress — 12 sites (7 getattr + 5 hasattr) across pt_expt/utils/serialization.py, pt_expt/model/make_model.py, jax/utils/serialization.py, deepmd/kernels/cuda/dpa1/canonical.py. Candidate: base-descriptor capability accessor.
• _fused_eligible — 4 sites (pt_expt/utils/serialization.py, kernels/triton/dpa1/{edge_conv,se_conv}.py, kernels/cuda/dpa1/canonical.py).
• tebd_compress, type_embd_data — jax/utils/serialization.py + assorted hasattr sites in dpmodel descriptors.

Fitting interface

• get_var_name — 9 hasattr sites; get_task_dim — 4; get_intensive — 4. Candidate: concrete defaults on make_base_fitting.
• reinit_exclude — dpmodel/atomic_model/dp_atomic_model.py via hasattr. Candidate: concrete no-op on make_base_fitting.

Atomic-model attributes

• pair_excl — 8 getattr(..., None) sites (dpmodel/pt_expt/jax/kernels). Dead-defensive if BaseAtomicModel.__init__ always sets it — verify, then make the direct attribute access the contract.
• pair_exclude_types — pt_expt/utils/serialization.py.

Dead-defensive probes of already-declared base methods (drop the probe, call directly)

• has_message_passing — 2 hasattr sites; has_default_fparam — 2 hasattr sites (e.g. jax/jax2tf/tfmodel.py).

Self-probes with defaults (attribute should be declared, not probed)

• use_loc_mapping — pt_expt/descriptor/repflows.py (getattr(self, ..., False)).
• set_davg_zero / set_stddev_constant — dpmodel/utils/env_mat_stat.py, pd/model/descriptor/descriptor.py.
• trainable — probed with INCONSISTENT defaults: True at pt_expt/descriptor/dpa4.py vs False at pt_expt/utils/network.py — an unpinned contract; decide the default once, declare it, and align both.

tf2 optional-feature hooks

• set_enable_compile, _call_common_lower_formatted — tf2/train/trainer.py (getattr(model, ..., None) then call-if-present). Candidate: declared no-op hooks on the base model.

Explicitly out of scope (legitimate duck typing, not the disease)

• getattr(torch.ops.deepmd, "...", None) custom-op registry probes (ops genuinely optional at runtime).
• serialize/deserialize protocol checks in the generic pt_expt wrapper machinery.
• Probes on external/non-deepmd objects (dtype, shape, dlpack, sess, ...).
• deepmd/tf (TF1) and deepmd/pt legacy trees (frozen; base declarations still propagate to their classes where the factories are shared).

Notes

• Defaults must be concrete, not abstract, so descriptors/fittings across all backends need no change (the base factories are shared by dpmodel/pt/pd/tf).
• Base-class docstrings stay implementer-agnostic (no concrete descriptor names or mechanism names).
• Each promotion comes with a universal-suite assertion covering both branches (default and override), following DescriptorTestCase.test_capability_contract / ModelTestCase.test_has_spin.
• The pd has_spin probe trio found in the re-sweep has already been fixed on the DPA4 graph branch (direct calls).

Design caveats (apply per item before promoting)

1. Guard against base-interface bloat. Every capability method that only a handful of subclasses override widens the shared base interface (the charge-spin family alone adds ~5 methods). Admission criterion: promote only when the probe spans multiple backends/modules; for a single-call-site probe, first consider narrowing the call site instead of widening the base.
2. Kernel-eligibility attributes may belong on the kernel side, not the descriptor base. _fused_eligible (and to a degree geo_compress) are kernel/backend implementation concerns, not descriptor domain semantics — promoting an underscore-private name into the shared backend-agnostic base leaks kernel concerns into dpmodel. Alternative to evaluate per item: let the kernel layer own the eligibility check ("can I fuse this descriptor?") rather than the descriptor declaring "I am fusable".
3. pair_excl: verification must precede deletion. Making direct attribute access the contract is valid only after verifying that BaseAtomicModel.__init__ unconditionally sets it on every construction path (including deserialize). Deleting the defensive getattr(..., None) probes first orphans that precondition — enumerate the paths, then drop the probes.

Triage (2026-08-11, applies the caveats above per item)

A. Promote to a base interface

B. Pin the contract (no new method; tighten the invariant)

C. Narrow fix (family-/call-site-local; do NOT widen the base)

D. Leave as-is (kernel-/single-backend-local protocols)

[amended during implementation] tf2/train/trainer.py's set_enable_compile / _call_common_lower_formatted and _fused_eligible were left as-is per this table, as originally triaged. During the residual audit, the atom_excl getattr siblings (e.g. deepmd/kernels/cuda/dpa1/canonical.py:44) were confirmed to be the same duck-typing disease but are outside this issue's inventory entirely (issue text never listed atom_excl) — candidate follow-up issue, not fixed here.

Cross-cutting

1. hasattr semantic inversion: the flagged sites in table A cannot be mechanically replaced — each must become a value check.
2. Every promotion ships the dual-branch (default + override) universal-suite assertion; pair_excl ships the construction-path assertion instead.