Don't silence TypeErrors in fmt_{x,y}data.

anntzer · anntzer · commit b4db19656c2e · 2018-10-28T12:33:28.000+01:00
Still in the "fewer ways to shoot oneself in the foot" spirit.
diff --git a/doc/api/next_api_changes/2018-10-27-AL.rst b/doc/api/next_api_changes/2018-10-27-AL.rst
@@ -0,0 +1,7 @@
+``Axes.fmt_xdata`` and ``Axes.fmt_ydata`` no longer ignore TypeErrors raised by a user-provided formatter
+`````````````````````````````````````````````````````````````````````````````````````````````````````````
+
+Previously, if the user provided a ``fmt_xdata`` or ``fmt_ydata`` function that
+raised a TypeError (or set them to a non-callable), the exception would be
+silently ignored and the default formatter be used instead.  This is no longer
+the case; the exception is now propagated out.
diff --git a/lib/matplotlib/axes/_base.py b/lib/matplotlib/axes/_base.py
@@ -3700,32 +3700,26 @@ def yaxis_date(self, tz=None):
 
     def format_xdata(self, x):
         """
-        Return *x* string formatted.  This function will use the attribute
-        self.fmt_xdata if it is callable, else will fall back on the xaxis
-        major formatter
+        Return *x* formatted as an x-value.
+
+        This function will use the `.fmt_xdata` attribute if it is not None,
+        else will fall back on the xaxis major formatter.
         """
-        try:
-            return self.fmt_xdata(x)
-        except TypeError:
-            func = self.xaxis.get_major_formatter().format_data_short
-            val = func(x)
-            return val
+        return (self.fmt_xdata if self.fmt_xdata is not None
+                else self.xaxis.get_major_formatter().format_data_short)(x)
 
     def format_ydata(self, y):
         """
-        Return y string formatted.  This function will use the
-        :attr:`fmt_ydata` attribute if it is callable, else will fall
-        back on the yaxis major formatter
+        Return *y* formatted as an y-value.
+
+        This function will use the `.fmt_ydata` attribute if it is not None,
+        else will fall back on the yaxis major formatter.
         """
-        try:
-            return self.fmt_ydata(y)
-        except TypeError:
-            func = self.yaxis.get_major_formatter().format_data_short
-            val = func(y)
-            return val
+        return (self.fmt_ydata if self.fmt_ydata is not None
+                else self.yaxis.get_major_formatter().format_data_short)(y)
 
     def format_coord(self, x, y):
-        """Return a format string formatting the *x*, *y* coord"""
+        """Return a format string formatting the *x*, *y* coordinates."""
         if x is None:
             xs = '???'
         else:
diff --git a/lib/matplotlib/tests/test_backend_bases.py b/lib/matplotlib/tests/test_backend_bases.py
@@ -1,3 +1,5 @@
+import re
+
 from matplotlib.backend_bases import (
     FigureCanvasBase, LocationEvent, RendererBase)
 import matplotlib.pyplot as plt
@@ -71,22 +73,26 @@ def test_non_gui_warning():
                 in str(rec[0].message))
 
 
-def test_location_event_position():
-    # LocationEvent should cast its x and y arguments
-    # to int unless it is None
-    fig = plt.figure()
+@pytest.mark.parametrize(
+    "x, y", [(42, 24), (None, 42), (None, None), (200, 100.01), (205.75, 2.0)])
+def test_location_event_position(x, y):
+    # LocationEvent should cast its x and y arguments to int unless it is None.
+    fig, ax = plt.subplots()
     canvas = FigureCanvasBase(fig)
-    test_positions = [(42, 24), (None, 42), (None, None),
-                      (200, 100.01), (205.75, 2.0)]
-    for x, y in test_positions:
-        event = LocationEvent("test_event", canvas, x, y)
-        if x is None:
-            assert event.x is None
-        else:
-            assert event.x == int(x)
-            assert isinstance(event.x, int)
-        if y is None:
-            assert event.y is None
-        else:
-            assert event.y == int(y)
-            assert isinstance(event.y, int)
+    event = LocationEvent("test_event", canvas, x, y)
+    if x is None:
+        assert event.x is None
+    else:
+        assert event.x == int(x)
+        assert isinstance(event.x, int)
+    if y is None:
+        assert event.y is None
+    else:
+        assert event.y == int(y)
+        assert isinstance(event.y, int)
+    if x is not None and y is not None:
+        assert re.match(
+            "x={} +y={}".format(ax.format_xdata(x), ax.format_ydata(y)),
+            ax.format_coord(x, y))
+        ax.fmt_xdata = ax.fmt_ydata = lambda x: "foo"
+        assert re.match("x=foo +y=foo", ax.format_coord(x, y))
