FIX: make set_text(None) keep string empty instead of "None" (#10392)

jklymak · efiring · commit 84292c469029 · 2018-02-14T10:24:37.000-10:00
* FIX: make set_text(None) keep string empty
diff --git a/doc/api/next_api_changes/2018-02-07-JMK.rst b/doc/api/next_api_changes/2018-02-07-JMK.rst
@@ -0,0 +1,9 @@
+`Text.set_text` with string argument ``None`` sets string to empty
+------------------------------------------------------------------
+
+`Text.set_text` when passed a string value of ``None`` would set the
+string to ``"None"``, so subsequent calls to `Text.get_text` would return
+the ambiguous ``"None"`` string.
+
+This change sets text objects passed ``None`` to have empty strings, so that
+`Text.get_text` returns and an empty string.
diff --git a/lib/matplotlib/legend.py b/lib/matplotlib/legend.py
@@ -1103,16 +1103,18 @@ def set_title(self, title, prop=None):
         with *prop* parameter.
         """
         self._legend_title_box._text.set_text(title)
+        if title:
+            self._legend_title_box._text.set_visible(True)
+            self._legend_title_box.set_visible(True)
+        else:
+            self._legend_title_box._text.set_visible(False)
+            self._legend_title_box.set_visible(False)
 
         if prop is not None:
             if isinstance(prop, dict):
                 prop = FontProperties(**prop)
             self._legend_title_box._text.set_fontproperties(prop)
 
-        if title:
-            self._legend_title_box.set_visible(True)
-        else:
-            self._legend_title_box.set_visible(False)
         self.stale = True
 
     def get_title(self):
diff --git a/lib/matplotlib/tests/test_legend.py b/lib/matplotlib/tests/test_legend.py
@@ -517,3 +517,14 @@ def test_shadow_framealpha():
     ax.plot(range(100), label="test")
     leg = ax.legend(shadow=True, facecolor='w')
     assert leg.get_frame().get_alpha() == 1
+
+
+def test_legend_title_empty():
+    # test that if we don't set the legend title, that
+    # it comes back as an empty string, and that it is not
+    # visible:
+    fig, ax = plt.subplots()
+    ax.plot(range(10))
+    leg = ax.legend()
+    assert leg.get_title().get_text() == ""
+    assert leg.get_title().get_visible() is False
diff --git a/lib/matplotlib/text.py b/lib/matplotlib/text.py
@@ -158,6 +158,7 @@ def __init__(self,
         elif isinstance(fontproperties, six.string_types):
             fontproperties = FontProperties(fontproperties)
 
+        self._text = ''
         self.set_text(text)
         self.set_color(color)
         self.set_usetex(usetex)
@@ -1158,14 +1159,18 @@ def set_verticalalignment(self, align):
 
     def set_text(self, s):
         """
-        Set the text string *s*
+        Set the text string *s*.
 
         It may contain newlines (``\\n``) or math in LaTeX syntax.
 
-        ACCEPTS: string or anything printable with '%s' conversion.
+        ACCEPTS: string or object castable to string, except
+        ``None``, which is set to an empty string.
         """
-        self._text = '%s' % (s,)
-        self.stale = True
+        if s is None:
+            s = ''
+        if s != self._text:
+            self._text = '%s' % (s,)
+            self.stale = True
 
     @staticmethod
     def is_math_text(s, usetex=None):
