Convert date x-values per stairs segment

Author: robertoffmoura

plotly/matplotlylib/renderer.py

@@ -795,15 +795,27 @@ def _draw_step_path(self, props):
             self.msg += "    Step path is not in data coordinates, not drawing\n"
             return
         style = props["style"]
+        segments = []
+        segment_x = []
+        segment_y = []
+        for (x0, y0), code in zip(props["data"], props["pathcodes"]):
+            if code == "M" and segment_x:
+                segments.append((segment_x, segment_y))
+                segment_x = []
+                segment_y = []
+            if not segment_x or x0 != segment_x[-1] or y0 != segment_y[-1]:
+                segment_x.append(x0)
+                segment_y.append(y0)
+        if segment_x:
+            segments.append((segment_x, segment_y))
         x = []
         y = []
-        for (x0, y0), code in zip(props["data"], props["pathcodes"]):
-            if code == "M" and x:
+        for sub_x, sub_y in segments:
+            if x:
                 x.append(None)
                 y.append(None)
-            if not x or x0 != x[-1] or y0 != y[-1]:
-                x.append(x0)
-                y.append(y0)
+            x.extend(self._convert_x_dates(sub_x))
+            y.extend(sub_y)
         if len(x) < 2:
             self.msg += "    Step path has fewer than 2 points, not drawing\n"
             return

plotly/matplotlylib/tests/test_renderer.py

@@ -594,6 +594,21 @@ def test_stairs_nan_values_split_into_disjoint_steps():
     assert tuple(trace.y) == (0.2, 1.0, 1.0, 0.2, None, 0.2, 0.5, 0.5, 0.2)
 
 
+def test_stairs_date_xaxis_with_nan_values():
+    """NaN-separated stairs on a date axis must export date strings."""
+    dates = [
+        datetime.datetime(2023, 1, 1) + datetime.timedelta(days=i) for i in range(4)
+    ]
+    fig, ax = plt.subplots()
+    ax.stairs([1.0, np.nan, 0.5], dates)
+
+    plotly_fig = tls.mpl_to_plotly(fig)
+
+    trace = plotly_fig.data[0]
+    assert None in trace.x
+    assert all(isinstance(x, str) or x is None for x in trace.x)
+
+
 def test_stairs_label_used_in_legend():
     """A labeled stairs patch must become a named legend entry."""
     fig, ax = plt.subplots()