Address local-review findings + fix test_practitioner.py mock fixture

Found via local pre-PR validation (wider polymorphic-consumer pytest
sweep + adversarial probe + local AI review).

1. Fix `mock_continuous_results` fixture in tests/test_practitioner.py.
   The fixture was setting `r.overall_se = 0.1` on a fresh
   `ContinuousDiDResults.__new__()` mock. Pre-PR this silently created a
   junk attribute (canonical SE on ContinuousDiDResults is
   `overall_att_se`); post-PR `overall_se` is a read-only @Property alias
   added by this PR, so the assignment raised `AttributeError: can't set
   attribute`. Changed to assign the canonical `overall_att_se` field.
   `_handle_continuous` in practitioner.py never reads the SE field
   anyway — only `_check_nan_att(results)` reads `att`/`overall_att`.

2. Lock read-only alias semantics with a regression test
   (`test_aliases_are_read_only` parametrized over Pattern B / C / D)
   so future contributors who write similar fixtures fail loudly via
   this test rather than via a surprise AttributeError in another suite.

3. One-sentence REGISTRY.md note that aliases are @Property descriptors
   and therefore do NOT appear in `dataclasses.fields()` or
   `dataclasses.asdict()` output, and that assignment raises
   AttributeError — so serializers and field-walkers continue to see
   only the canonical field set.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: igerber

docs/methodology/REGISTRY.md

@@ -2,7 +2,7 @@
 
 This document provides the academic foundations and key implementation requirements for each estimator in diff-diff. It serves as a reference for contributors and users who want to understand the theoretical basis of the methods.
 
-**Result-class field naming.** Headline scalar inference fields appear under one of four native naming patterns: flat `att` / `se` / `conf_int` / `p_value` / `t_stat` (`DiDResults`, `SyntheticDiDResults`, `TROPResults`, `HeterogeneousAdoptionDiDResults`); `overall_*` (`CallawaySantAnnaResults` and the rest of the staggered family); `overall_att_*` (`ContinuousDiDResults`, where `att` and `acrt` are parallel response curves); and `avg_*` (`MultiPeriodDiDResults`). Every scalar treatment-effect result class covered by this naming contract additionally exposes the flat `att` / `se` / `conf_int` / `p_value` / `t_stat` names as read-only `@property` aliases for adapter / external-consumer compatibility (see PR for v3.3.3, motivated by `balance.interop.diff_diff`); `ContinuousDiDResults` further exposes `overall_*` aliases pointing at the ATT side. The native field is canonical for documentation, semantics, and computation — aliases are pure read-throughs and inherit the `safe_inference()` joint-NaN consistency contract automatically.
+**Result-class field naming.** Headline scalar inference fields appear under one of four native naming patterns: flat `att` / `se` / `conf_int` / `p_value` / `t_stat` (`DiDResults`, `SyntheticDiDResults`, `TROPResults`, `HeterogeneousAdoptionDiDResults`); `overall_*` (`CallawaySantAnnaResults` and the rest of the staggered family); `overall_att_*` (`ContinuousDiDResults`, where `att` and `acrt` are parallel response curves); and `avg_*` (`MultiPeriodDiDResults`). Every scalar treatment-effect result class covered by this naming contract additionally exposes the flat `att` / `se` / `conf_int` / `p_value` / `t_stat` names as read-only `@property` aliases for adapter / external-consumer compatibility (see PR for v3.3.3, motivated by `balance.interop.diff_diff`); `ContinuousDiDResults` further exposes `overall_*` aliases pointing at the ATT side. The native field is canonical for documentation, semantics, and computation — aliases are pure read-throughs and inherit the `safe_inference()` joint-NaN consistency contract automatically. Because aliases are `@property` descriptors (not dataclass fields), they do NOT appear in `dataclasses.fields()` or `dataclasses.asdict()` output, and assignment to an alias raises `AttributeError`; serializers and field-walkers continue to see only the canonical field set.
 
 ## Table of Contents
 

tests/test_practitioner.py

@@ -126,7 +126,10 @@ def mock_efficient_results():
 def mock_continuous_results():
     r = ContinuousDiDResults.__new__(ContinuousDiDResults)
     r.overall_att = 0.4
-    r.overall_se = 0.1
+    # Canonical SE field on ContinuousDiDResults is overall_att_se (the ATT side).
+    # `overall_se` is a read-only property alias since the v3.3.3 inference-field
+    # alias surface; assigning to it raises AttributeError.
+    r.overall_att_se = 0.1
     return r
 
 

tests/test_result_aliases.py

@@ -258,6 +258,54 @@ def test_multi_period_did_aliases():
     assert res.t_stat == _T
 
 
+# ============================================================================
+# Read-only semantics
+# ============================================================================
+
+
+@pytest.mark.parametrize(
+    ("cls", "ovr"),
+    [
+        (
+            CallawaySantAnnaResults,
+            {
+                "overall_att": _ATT,
+                "overall_se": _SE,
+                "overall_t_stat": _T,
+                "overall_p_value": _P,
+                "overall_conf_int": _CI,
+            },
+        ),
+        (ContinuousDiDResults, _continuous_did_overrides()),
+        (
+            MultiPeriodDiDResults,
+            {
+                "avg_att": _ATT,
+                "avg_se": _SE,
+                "avg_t_stat": _T,
+                "avg_p_value": _P,
+                "avg_conf_int": _CI,
+            },
+        ),
+    ],
+    ids=lambda v: v.__name__ if hasattr(v, "__name__") else "ovr",
+)
+def test_aliases_are_read_only(cls, ovr):
+    """Assigning to an alias must raise AttributeError (no setter installed).
+
+    Regression: a downstream test in tests/test_practitioner.py used
+    `r.overall_se = X` on a `ContinuousDiDResults.__new__()` mock — pre-alias
+    that silently created a junk attribute; post-alias the property correctly
+    rejects the assignment. Locking read-only here means future contributors
+    who write similar fixtures fail loudly via this test rather than via a
+    surprise `AttributeError: can't set attribute` deep in another suite.
+    """
+    res = cls(**_required_init_kwargs(cls, ovr))
+    for name in ("att", "se", "conf_int", "p_value", "t_stat"):
+        with pytest.raises(AttributeError):
+            setattr(res, name, object())
+
+
 # ============================================================================
 # Cross-cutting regression — balance.interop.diff_diff adapter pattern
 # ============================================================================