fix: preserve unexpected peak refinement failures (#140)

* fix: preserve unexpected peak refinement failures

* test: cover peak fit warnings and error propagation

---------

Co-authored-by: Peter Corke <peter.i.corke@gmail.com>

Author: RoboX2020

src/machinevisiontoolbox/base/findpeaks.py

@@ -4,6 +4,8 @@
 
 from __future__ import annotations
 
+import warnings
+
 import numpy as np
 import scipy as sp
 import spatialmath.base as base
@@ -116,10 +118,13 @@ def findpeaks(
                 poly, *_ = Polynomial.fit(
                     x[i - n2 : i + n2 + 1], y[i - n2 : i + n2 + 1], interp, full=True
                 )
-            except:
-                # handle situation where neighbourhood falls off the data
-                # vector
-                print(f"Peak at {x[i]} couldn't be fitted, skipping")
+            except (ValueError, np.linalg.LinAlgError):
+                # A neighbourhood near the boundary can contain too few samples.
+                warnings.warn(
+                    f"Peak at {x[i]} couldn't be fitted, skipping",
+                    RuntimeWarning,
+                    stacklevel=2,
+                )
                 continue
 
             # find the roots of the polynomial closest to the coarse peak

tests/base/test_findpeaks.py

@@ -1,13 +1,34 @@
 import unittest
+from unittest.mock import patch
 
 import numpy as np
+from numpy.polynomial import Polynomial
 
 from machinevisiontoolbox import findpeaks, findpeaks2d, findpeaks3d
 
 
 class TestFindpeaks(unittest.TestCase):
     """Test cases for 1D peak finding"""
 
+    def test_failed_refinement_warns_and_skips(self):
+        """Warn when the fit neighbourhood extends beyond the signal."""
+        y = np.array([0, 2, 0, 0, 0, 0, 0], dtype=float)
+        with self.assertWarnsRegex(
+            RuntimeWarning, "Peak at 1 couldn't be fitted, skipping"
+        ):
+            x, ymax = findpeaks(y, interp=6, npeaks=1)
+        self.assertEqual(x.size, 0)
+        self.assertEqual(ymax.size, 0)
+
+    def test_refinement_preserves_unexpected_exceptions(self):
+        """Let unrelated failures and user interrupts reach the caller."""
+        y = np.array([0, 1, 2, 1, 0], dtype=float)
+        for error in (RuntimeError("unexpected failure"), KeyboardInterrupt()):
+            with self.subTest(error=type(error).__name__):
+                with patch.object(Polynomial, "fit", side_effect=error):
+                    with self.assertRaises(type(error)):
+                        findpeaks(y, interp=True)
+
     def test_simple_peak(self):
         """Test detection of simple peak"""
         y = np.array([0, 0, 1, 2, 0, 0, 0, 3, 1, 0, 0, 0, 0])