Fix ErrorBarCurveItem to handle all-NaN data gracefully and add corresponding tests

Author: PierreRaybaut

CHANGELOG.md

@@ -36,6 +36,10 @@
 🛠️ Bug fixes:
 
 * [Issue #46](https://github.com/PlotPyStack/PlotPy/issues/46) - Contrast adjustment with 'Eliminate outliers' failed for float images with high dynamic range
+* Fixed `ErrorBarCurveItem` handling of all-NaN data:
+  * Fixed `ValueError: zero-size array to reduction operation minimum which has no identity` when error bar curves contain only NaN values
+  * Added proper checks in `boundingRect()` and `draw()` methods to handle empty arrays gracefully
+  * Error bar curves with all-NaN data now fall back to parent class behavior instead of crashing
 * Item list: refresh tree when item parameters are changed:
   * Added `SIG_ITEM_PARAMETERS_CHANGED` signal to `BasePlot` class
   * This signal is emitted when the parameters of an item are changed using the parameters dialog, or a specific tool (e.g. the colormap selection tool, or the lock/unlock tool for image items)

plotpy/items/curve/errorbar.py

@@ -243,6 +243,11 @@ def boundingRect(self) -> QC.QRectF:
         plot: BasePlot = self.plot()
         xminf, yminf = xmin[np.isfinite(xmin)], ymin[np.isfinite(ymin)]
         xmaxf, ymaxf = xmax[np.isfinite(xmax)], ymax[np.isfinite(ymax)]
+
+        # If all values are NaN, return the parent's bounding rect
+        if 0 in (xminf.size, yminf.size, xmaxf.size, ymaxf.size):
+            return CurveItem.boundingRect(self)
+
         if plot is not None and "log" in (
             plot.get_axis_scale(self.xAxis()),
             plot.get_axis_scale(self.yAxis()),
@@ -272,6 +277,8 @@ def draw(
         if self._x is None or self._x.size == 0:
             return
         x, y, xmin, xmax, ymin, ymax = self.get_minmax_arrays(all_values=False)
+        if x.size == 0:  # All values are NaN
+            return
         tx = vmap(xMap, x)
         ty = vmap(yMap, y)
         RN = list(range(len(tx)))

plotpy/tests/unit/test_plot_curve.py

@@ -19,6 +19,26 @@
 )
 
 
+def test_plot_curve_anomalies():
+    """Test plotting of a curve with anomalies"""
+    x = np.array([0.0, 1.0, 2.0, 3.0, 4.0, 5.0])
+    dx = dy = y = x * np.nan
+
+    with qt_app_context(exec_loop=False):
+        win = make.dialog(toolbar=True, type="curve")
+        plot = win.manager.get_plot()
+        for curve in (
+            make.merror(x, y, label="Curve"),
+            make.merror(x, y, dx, label="Curve"),
+            make.merror(x, y, dy, label="Curve"),
+            make.merror(x, y, dx, dy, label="Curve"),
+        ):
+            plot.add_item(curve)
+        win.show()
+        plot.do_autoscale()  # Force autoscale (was crashing initially with NaN data)
+        exec_dialog(win)
+
+
 def test_plot_curve():
     """Test plotting of a curve with PlotDialog"""
     x = np.linspace(-10, 10, 200)
@@ -90,5 +110,6 @@ def test_plot_curve_anti_aliasing():
 
 
 if __name__ == "__main__":
-    test_plot_curve()
-    test_plot_curve_anti_aliasing()
+    test_plot_curve_anomalies()
+    # test_plot_curve()
+    # test_plot_curve_anti_aliasing()

test_nan_fix.py

@@ -0,0 +1,47 @@
+#!/usr/bin/env python3
+"""
+Test script to verify the NaN handling fix in ErrorBarCurveItem
+"""
+
+import numpy as np
+from guidata.qthelpers import qt_app_context
+
+from plotpy.builder import make
+
+
+def test_nan_errorbar_fix():
+    """Test that ErrorBarCurveItem handles all-NaN data gracefully"""
+    print("Testing ErrorBar curve with all-NaN data...")
+
+    with qt_app_context():
+        # Create data with all NaN values (this was causing the error)
+        x = np.array([0.0, 1.0, 2.0, 3.0, 4.0, 5.0])
+        y = np.array([0.0, 1.0, 0.0, 1.0, 0.0, 1.0]) * np.nan
+        dx = np.array([0.1, 0.1, 0.1, 0.1, 0.1, 0.1])
+        dy = np.array([0.1, 0.1, 0.1, 0.1, 0.1, 0.1])
+
+        # Create errorbar curve
+        curve = make.merror(x, y, dx, dy, title="Test curve with NaN")
+
+        # Test that boundingRect doesn't crash (this was the original issue)
+        try:
+            bbox = curve.boundingRect()
+            print(f"✓ boundingRect() succeeded: {bbox}")
+        except Exception as e:
+            print(f"✗ boundingRect() failed: {e}")
+            return False
+
+        # Test that get_minmax_arrays works
+        try:
+            _ = curve.get_minmax_arrays()
+            print("✓ get_minmax_arrays() succeeded")
+        except Exception as e:
+            print(f"✗ get_minmax_arrays() failed: {e}")
+            return False
+
+        print("✓ All tests passed! NaN handling fix is working correctly.")
+        return True
+
+
+if __name__ == "__main__":
+    test_nan_errorbar_fix()