From 86f68154852bcea9e33d8d809b1d403e2f35994e Mon Sep 17 00:00:00 2001
From: Chadwick Boulay <chadwick.boulay@gmail.com>
Date: Sun, 12 Jul 2026 21:03:32 -0400
Subject: [PATCH] Add passthrough mode to GaussianSmoothingFilterTransformer

Degenerate smoothing settings (sigma None or <= 0, width None or <= 0,
kernel_size <= 1) now disable smoothing: the transformer passes messages
through unchanged instead of raising. The design wrapper returns None
coefficients (rather than None from get_design_function) so passthrough
works on both the sync __call__ path and the async unit path, and can be
toggled live via update_settings.

kernel_size=1 previously designed a warning single-tap identity kernel;
it is now a silent passthrough. The standalone design function still
raises/warns as before.
---
 src/ezmsg/sigproc/gaussiansmoothing.py       | 12 +++-
 tests/unit/test_gaussian_smoothing_filter.py | 58 ++++++++++++++++++--
 2 files changed, 63 insertions(+), 7 deletions(-)

diff --git a/src/ezmsg/sigproc/gaussiansmoothing.py b/src/ezmsg/sigproc/gaussiansmoothing.py
index f0f01507..25a0b76b 100644
--- a/src/ezmsg/sigproc/gaussiansmoothing.py
+++ b/src/ezmsg/sigproc/gaussiansmoothing.py
@@ -84,8 +84,16 @@ def gaussian_smoothing_filter_design(
 class GaussianSmoothingFilterTransformer(FilterByDesignTransformer[GaussianSmoothingSettings, BACoeffs]):
     def get_design_function(
         self,
-    ) -> Callable[[float], BACoeffs]:
-        def design_wrapper(fs: float) -> BACoeffs:
+    ) -> Callable[[float], BACoeffs | None]:
+        def design_wrapper(fs: float) -> BACoeffs | None:
+            if (
+                self.settings.sigma is None
+                or self.settings.sigma <= 0
+                or self.settings.width is None
+                or self.settings.width <= 0
+                or (self.settings.kernel_size is not None and self.settings.kernel_size <= 1)
+            ):
+                return None
             return gaussian_smoothing_filter_design(
                 sigma=self.settings.sigma * fs,  # settings.sigma is in seconds
                 width=self.settings.width,
diff --git a/tests/unit/test_gaussian_smoothing_filter.py b/tests/unit/test_gaussian_smoothing_filter.py
index 5ab2c2d7..29491f9d 100644
--- a/tests/unit/test_gaussian_smoothing_filter.py
+++ b/tests/unit/test_gaussian_smoothing_filter.py
@@ -1,3 +1,6 @@
+import asyncio
+import warnings
+
 import numpy as np
 import pytest
 from ezmsg.util.messages.axisarray import AxisArray
@@ -275,13 +278,58 @@ def _kernel_len(fs: float) -> int:
     assert len_1000 == int(2 * 4 * 0.02 * 1000.0 + 1)
 
 
-def test_gaussian_identity_kernel_warns_and_passes_through():
-    """An explicit single-tap kernel warns and leaves the data unchanged."""
-    proc = GaussianSmoothingFilterTransformer(GaussianSmoothingSettings(sigma=0.02, kernel_size=1, axis="time"))
+def test_gaussian_identity_kernel_design_warns():
+    """The standalone design function still warns for a single-tap kernel."""
+    with pytest.warns(UserWarning, match="identity"):
+        gaussian_smoothing_filter_design(sigma=2.0, kernel_size=1)
+
+
+@pytest.mark.parametrize(
+    "settings_kwargs",
+    [
+        {"sigma": None},
+        {"sigma": 0.0},
+        {"sigma": -0.01},
+        {"width": None},
+        {"width": 0},
+        {"width": -2},
+        {"kernel_size": 0},
+        {"kernel_size": 1},
+        {"kernel_size": -1},
+    ],
+)
+def test_gaussian_passthrough_settings(settings_kwargs):
+    """Degenerate settings disable smoothing: input passes through unchanged, silently."""
+    proc = GaussianSmoothingFilterTransformer(GaussianSmoothingSettings(axis="time", **settings_kwargs))
     msg = make_msg()
-    with pytest.warns(UserWarning):
+    with warnings.catch_warnings():
+        warnings.simplefilter("error")
         result = proc(msg)
-    assert np.allclose(result.data, msg.data)
+    assert result.data is msg.data
+    assert proc.state.filter.settings.coefs is None
+
+
+def test_gaussian_passthrough_async_path():
+    """The async unit path (__acall__ -> _aprocess) bypasses the sync __call__
+    shortcut, so passthrough must survive it too."""
+    proc = GaussianSmoothingFilterTransformer(GaussianSmoothingSettings(axis="time", sigma=0.0))
+    msg = make_msg()
+    result = asyncio.run(proc.__acall__(msg))
+    assert result.data is msg.data
+
+
+def test_gaussian_passthrough_toggle():
+    """Smoothing can be disabled and re-enabled live via update_settings."""
+    proc = GaussianSmoothingFilterTransformer(GaussianSmoothingSettings(axis="time", sigma=0.0))
+    msg = make_msg()
+    assert proc(msg).data is msg.data
+
+    proc.update_settings(sigma=0.02)  # 2 samples at 100 Hz
+    smoothed = proc(msg)
+    assert not np.allclose(smoothed.data, msg.data)
+
+    proc.update_settings(sigma=0.0)
+    assert proc(msg).data is msg.data
 
 
 def test_gaussian_empty_after_init():