FIX: ensure errorbar creates line collection even with empty data

tacaswell · tacaswell · commit af904fc3db5f · 2017-11-07T02:09:11.000-05:00
closes #9699
diff --git a/lib/matplotlib/axes/_axes.py b/lib/matplotlib/axes/_axes.py
@@ -3033,7 +3033,7 @@ def extract_err(err, data):
             # select points without upper/lower limits in x and
             # draw normal errorbars for these points
             noxlims = ~(xlolims | xuplims)
-            if noxlims.any():
+            if noxlims.any() or len(noxlims) == 0:
                 yo, _ = xywhere(y, right, noxlims & everymask)
                 lo, ro = xywhere(left, right, noxlims & everymask)
                 barcols.append(self.hlines(yo, lo, ro, **eb_lines_style))
@@ -3082,7 +3082,7 @@ def extract_err(err, data):
             # select points without upper/lower limits in y and
             # draw normal errorbars for these points
             noylims = ~(lolims | uplims)
-            if noylims.any():
+            if noylims.any() or len(noylims) == 0:
                 xo, _ = xywhere(x, lower, noylims & everymask)
                 lo, uo = xywhere(lower, upper, noylims & everymask)
                 barcols.append(self.vlines(xo, lo, uo, **eb_lines_style))
diff --git a/lib/matplotlib/tests/test_axes.py b/lib/matplotlib/tests/test_axes.py
@@ -5402,3 +5402,10 @@ def test_polar_gridlines():
 
     assert ax.xaxis.majorTicks[0].gridline.get_alpha() == .2
     assert ax.yaxis.majorTicks[0].gridline.get_alpha() == .2
+
+
+def test_empty_errorbar_legend():
+    fig, ax = plt.subplots()
+    ax.errorbar([], [], xerr=[], label='empty y')
+    ax.errorbar([], [], yerr=[], label='empty x')
+    ax.legend()
