Backport PR #13209: Deprecate support for (n, 1)-shaped error arrays in errorbar().

tacaswell · MeeseeksDev[bot] · commit 5dc047428a61 · 2019-02-23T18:25:54.000Z
diff --git a/doc/api/next_api_changes/2019-01-18-AL.rst b/doc/api/next_api_changes/2019-01-18-AL.rst
@@ -0,0 +1,6 @@
+Deprecations
+````````````
+
+Support for passing (n, 1)-shaped error arrays to errorbar(), which was not
+documented and did not work for ``n = 2``, is deprecated (pass a 1D array
+instead).
diff --git a/lib/matplotlib/axes/_axes.py b/lib/matplotlib/axes/_axes.py
@@ -3309,6 +3309,12 @@ def extract_err(err, data):
                     or len(b_sh) > 2 or (len(b_sh) == 2 and b_sh[1] != 1)):
                 raise ValueError(
                     "err must be a scalar or a 1D or (2, n) array-like")
+            if len(a_sh) == 2 or len(b_sh) == 2:
+                cbook.warn_deprecated(
+                    "3.1", message="Support for passing a (n, 1)-shaped error "
+                    "array to errorbar() is deprecated since Matplotlib "
+                    "%(since)s and will be removed %(removal)s; pass a 1D "
+                    "array instead.")
             # Using list comprehensions rather than arrays to preserve units.
             for e in [a, b]:
                 if len(data) != len(e):
diff --git a/lib/matplotlib/tests/test_axes.py b/lib/matplotlib/tests/test_axes.py
@@ -2838,7 +2838,8 @@ def test_errorbar():
     fig, axs = plt.subplots(nrows=2, ncols=2, sharex=True)
     ax = axs[0, 0]
     # Try a Nx1 shaped error just to check
-    ax.errorbar(x, y, yerr=np.reshape(yerr, (len(y), 1)), fmt='o')
+    with pytest.warns(MatplotlibDeprecationWarning):
+        ax.errorbar(x, y, yerr=np.reshape(yerr, (len(y), 1)), fmt='o')
     ax.set_title('Vert. symmetric')
 
     # With 4 subplots, reduce the number of axis ticks to avoid crowding.
@@ -5216,9 +5217,12 @@ def generate_errorbar_inputs():
 
 @pytest.mark.parametrize('kwargs', generate_errorbar_inputs())
 def test_errorbar_inputs_shotgun(kwargs):
-    ax = plt.gca()
-    eb = ax.errorbar(**kwargs)
-    eb.remove()
+    with warnings.catch_warnings():
+        # (n, 1)-shaped error deprecation already tested by test_errorbar.
+        warnings.simplefilter("ignore", MatplotlibDeprecationWarning)
+        ax = plt.gca()
+        eb = ax.errorbar(**kwargs)
+        eb.remove()
 
 
 @image_comparison(baseline_images=["dash_offset"], remove_text=True)
