Merge pull request matplotlib#25624 from tacaswell/fix/tightlayout_autolayout

FIX: correctly unset the layout engine in Figure.tight_layout

Author: oscargus

lib/matplotlib/figure.py

@@ -3515,7 +3515,7 @@ def tight_layout(self, *, pad=1.08, h_pad=None, w_pad=None, rect=None):
                     and previous_engine is not None:
                 _api.warn_external('The figure layout has changed to tight')
         finally:
-            self.set_layout_engine(None)
+            self.set_layout_engine('none')
 
 
 def figaspect(arg):

lib/matplotlib/tests/test_figure.py

@@ -659,6 +659,15 @@ def test_invalid_layouts():
         fig.set_layout_engine("constrained")
 
 
+@check_figures_equal(extensions=["png"])
+def test_tightlayout_autolayout_deconflict(fig_test, fig_ref):
+    for fig, autolayout in zip([fig_ref, fig_test], [False, True]):
+        with mpl.rc_context({'figure.autolayout': autolayout}):
+            axes = fig.subplots(ncols=2)
+            fig.tight_layout(w_pad=10)
+        assert isinstance(fig.get_layout_engine(), PlaceHolderLayoutEngine)
+
+
 @pytest.mark.parametrize('layout', ['constrained', 'compressed'])
 def test_layout_change_warning(layout):
     """