Backport PR #10064: FIX: remove repeated label legend logic

dstansby · MeeseeksDev[bot] · commit c0fc4e2dcd04 · 2017-12-21T09:18:11.000Z
diff --git a/doc/api/api_changes.rst b/doc/api/api_changes.rst
@@ -10,6 +10,29 @@ out what caused the breakage and how to fix it by updating your code.
 For new features that were added to Matplotlib, please see
 :ref:`whats-new`.
 
+API Changes in 2.1.2
+====================
+
+`Figure.legend` no longer checks for repeated lines to ignore
+-------------------------------------------------------------
+
+`matplotlib.Figure.legend` used to check if a line had the
+same label as an existing legend entry. If it also had the same line color
+or marker color legend didn't add a new entry for that line. However, the
+list of conditions was incomplete, didn't handle RGB tupples,
+didn't handle linewidths or linestyles etc.
+
+This logic did not exist in `Axes.legend`.  It was included (erroneously)
+in Matplotlib 2.1.1 when the legend argument parsing was unified
+[#9324](https://github.com/matplotlib/matplotlib/pull/9324).  This change
+removes that check in `Axes.legend` again to restore the old behavior.
+
+This logic has also been dropped from `.Figure.legend`, where it
+was previously undocumented. Repeated
+lines with the same label will now each have an entry in the legend.  If
+you do not want the duplicate entries, don't add a label to the line, or
+prepend the label with an underscore.
+
 API Changes in 2.1.1
 ====================
 
diff --git a/lib/matplotlib/legend.py b/lib/matplotlib/legend.py
@@ -1325,43 +1325,9 @@ def _get_legend_handles_labels(axs, legend_handler_map=None):
     handles = []
     labels = []
 
-    def _in_handles(h, l):
-        # Method to check if we already have a given handle and label.
-        # Consider two handles to be the same if they share a label,
-        # color, facecolor, and edgecolor.
-
-        # Loop through each handle and label already collected
-        for f_h, f_l in zip(handles, labels):
-            if f_l != l:
-                continue
-            if type(f_h) != type(h):
-                continue
-            try:
-                if (colors.to_rgba_array(f_h.get_color()) !=
-                        colors.to_rgba_array(h.get_color())).any():
-                    continue
-            except AttributeError:
-                pass
-            try:
-                if (colors.to_rgba_array(f_h.get_facecolor()) !=
-                        colors.to_rgba_array(h.get_facecolor())).any():
-                    continue
-            except AttributeError:
-                pass
-            try:
-                if (colors.to_rgba_array(f_h.get_edgecolor()) !=
-                        colors.to_rgba_array(h.get_edgecolor())).any():
-                    continue
-            except AttributeError:
-                pass
-            return True
-        return False
-
     for handle in _get_legend_handles(axs, legend_handler_map):
         label = handle.get_label()
-        if (label and
-                not label.startswith('_') and
-                not _in_handles(handle, label)):
+        if (label and not label.startswith('_')):
             handles.append(handle)
             labels.append(label)
     return handles, labels
diff --git a/lib/matplotlib/tests/test_figure.py b/lib/matplotlib/tests/test_figure.py
@@ -90,7 +90,7 @@ def test_figure_legend():
     axes[0].plot([0, 1], [0, 1], label='y', color='r')
     axes[0].plot([0, 1], [0.5, 0.5], label='y', color='k')
 
-    axes[1].plot([0, 1], [1, 0], label='y', color='r')
+    axes[1].plot([0, 1], [1, 0], label='_y', color='r')
     axes[1].plot([0, 1], [0, 1], label='z', color='b')
     fig.legend()
 
diff --git a/lib/matplotlib/tests/test_legend.py b/lib/matplotlib/tests/test_legend.py
@@ -16,6 +16,7 @@
 import matplotlib.transforms as mtransforms
 import matplotlib.collections as mcollections
 from matplotlib.legend_handler import HandlerTuple
+import matplotlib.legend as mlegend
 import inspect
 
 
@@ -418,6 +419,21 @@ def test_nanscatter():
     ax.grid(True)
 
 
+def test_legend_repeatcheckok():
+    fig, ax = plt.subplots()
+    ax.scatter(0.0, 1.0, color='k', marker='o', label='test')
+    ax.scatter(0.5, 0.0, color='r', marker='v', label='test')
+    hl = ax.legend()
+    hand, lab = mlegend._get_legend_handles_labels([ax])
+    assert len(lab) == 2
+    fig, ax = plt.subplots()
+    ax.scatter(0.0, 1.0, color='k', marker='o', label='test')
+    ax.scatter(0.5, 0.0, color='k', marker='v', label='test')
+    hl = ax.legend()
+    hand, lab = mlegend._get_legend_handles_labels([ax])
+    assert len(lab) == 2
+
+
 @image_comparison(baseline_images=['not_covering_scatter'], extensions=['png'])
 def test_not_covering_scatter():
     colors = ['b', 'g', 'r']
