vline etc. can be added to single plot now

without breaking previous _add_annotation_like behaviour.

Author: nicholas-esterer

packages/python/plotly/plotly/basedatatypes.py

@@ -1193,14 +1193,6 @@ def _add_annotation_like(
             xref, yref = xaxis.replace("axis", ""), yaxis.replace("axis", "")
             new_obj.update(xref=xref, yref=yref)
 
-        # xref and yref are set to the first axes if not set.
-        # This is so that routines that need these to be specified if row and
-        # col were not specified can still work (e.g., `add_vline`).
-        if new_obj.xref is None:
-            new_obj.xref = "x"
-        if new_obj.yref is None:
-            new_obj.yref = "y"
-
         self.layout[prop_plural] += (new_obj,)
 
         return self
@@ -3549,6 +3541,14 @@ def _process_multiple_paper_spanning_shapes(
         # the new shapes that were added at the end
         n_shapes_before = len(self.layout["shapes"])
         self.add_shape(row=row, col=col, **shape_args, **kwargs)
+        if row == None and col == None:
+            # this was called intending to add to a single plot (and
+            # self.add_shape succeeded)
+            # however, in the case of a single plot, xref and yref are not
+            # specified, so we specify them here to the following routines can work
+            # (they need to change xref or yref to paper and change their range
+            # to the domain)
+            self.layout["shapes"][-1].update(xref="x", yref="y")
         n_shapes_after = len(self.layout["shapes"])
         new_shapes = tuple(
             filter(

packages/python/plotly/plotly/tests/test_core/test_update_objects/test_paper_span_shapes.py

@@ -369,14 +369,28 @@ def test_add_span_shape_no_empty_plot(
                 {
                     "type": "line",
                     "x0": 0,
-                    "x1": 0.4,
+                    "x1": 1,
                     "xref": "paper",
                     "y0": 6,
                     "y1": 6,
                     "yref": "y",
                 }
             ],
-        )
+        ),
+        (
+            (go.Figure.add_vline, dict(x=6)),
+            [
+                {
+                    "type": "line",
+                    "y0": 0,
+                    "y1": 1,
+                    "xref": "x",
+                    "x0": 6,
+                    "x1": 6,
+                    "yref": "paper",
+                }
+            ],
+        ),
     ],
 )
 def test_non_subplot_add_span_shape(test_input, expected, non_subplot_fig_fixture):