Backport PR #17938: Don't allow 1D lists as subplot_moasic layout.

jklymak · meeseeksmachine · commit 0c9799eb4082 · 2020-07-15T22:48:54.000Z
diff --git a/lib/matplotlib/figure.py b/lib/matplotlib/figure.py
@@ -1614,6 +1614,8 @@ def _make_array(inp):
             """
             r0, *rest = inp
             for j, r in enumerate(rest, start=1):
+                if isinstance(r, str):
+                    raise ValueError('List layout specification must be 2D')
                 if len(r0) != len(r):
                     raise ValueError(
                         "All of the rows must be the same length, however "
diff --git a/lib/matplotlib/tests/test_figure.py b/lib/matplotlib/tests/test_figure.py
@@ -728,6 +728,10 @@ def test_empty(self, fig_test, fig_ref, x, empty_sentinel):
         axB = fig_ref.add_subplot(gs[1, 1])
         axB.set_title(labels[1])
 
+    def test_fail_list_of_str(self):
+        with pytest.raises(ValueError, match='must be 2D'):
+            plt.subplot_mosaic(['foo', 'bar'])
+
     @check_figures_equal(extensions=["png"])
     @pytest.mark.parametrize("subplot_kw", [{}, {"projection": "polar"}, None])
     def test_subplot_kw(self, fig_test, fig_ref, subplot_kw):
