add test and remove warn parameter

zhoubecky · zhoubecky · commit 63f468ec8807 · 2018-03-14T16:19:53.000-04:00
diff --git a/lib/matplotlib/backend_bases.py b/lib/matplotlib/backend_bases.py
@@ -175,7 +175,7 @@ def draw_if_interactive(cls):
                 cls.trigger_manager_draw(manager)
 
     @classmethod
-    def show(cls, block=None, warn=True):
+    def show(cls, block=None):
         """Show all figures.
 
         `show` blocks by calling `mainloop` if *block* is ``True``, or if it
@@ -189,11 +189,10 @@ def show(cls, block=None, warn=True):
             try:
                 manager.show()
             except NonGuiException:
-                if warn:
-                    import warnings
-                    warnings.warn(
-                        "matplotlib is currently using a non-GUI backend, "
-                        "so cannot show the figure")
+                import warnings
+                warnings.warn(
+                    "matplotlib is currently using a non-GUI backend, "
+                    "so cannot show the figure")
                 return
         if cls.mainloop is None:
             return
diff --git a/lib/matplotlib/tests/test_backend_svg.py b/lib/matplotlib/tests/test_backend_svg.py
@@ -179,3 +179,22 @@ def psfont(*args, **kwargs):
     ax.text(0.5, 0.5, 'hello')
     with tempfile.TemporaryFile() as tmpfile, pytest.raises(ValueError):
         fig.savefig(tmpfile, format='svg')
+
+
+def test_NonGui_warning():
+    matplotlib.use('Agg')
+    import matplotlib.pyplot as plt
+    plt.plot([1, 2, 3])
+    plt.savefig('myfig')
+
+    with pytest.warns(UserWarning) as rec:
+        plt.show()
+        assert len(rec) == 1
+        assert 'matplotlib is currently using a non-GUI backend' \
+               in str(rec[0].message)
+
+    with pytest.warns(UserWarning) as rec:
+        plt.gcf().show()
+        assert len(rec) == 1
+        assert 'matplotlib is currently using a non-GUI backend' \
+               in str(rec[0].message)
