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FIX: behaviour of legend labels with leading underscores did not adhere to the API documentation #24713

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FIX: behaviour of legend labels with leading underscores did not adhere to the API documentation #24713

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fe9e9e9
Fixed behaviour of matplotlib.legend.Legend with respect to the handl…
Klayto-235 Dec 13, 2022
e54aeed
Adapted tests for the previous fix.
Klayto-235 Dec 13, 2022
73da1bc
Fixed newly failing tests
Klayto-235 Dec 13, 2022
abad6cc
Implemented more complete test
Klayto-235 Dec 13, 2022
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18 changes: 2 additions & 16 deletions lib/matplotlib/legend.py
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Original file line number Diff line number Diff line change
Expand Up @@ -22,7 +22,6 @@
"""

import itertools
import logging
import time

import numpy as np
Expand Down Expand Up @@ -418,17 +417,6 @@ def val_or_rc(val, rc_name):
self.borderaxespad = val_or_rc(borderaxespad, 'legend.borderaxespad')
self.columnspacing = val_or_rc(columnspacing, 'legend.columnspacing')
self.shadow = val_or_rc(shadow, 'legend.shadow')
# trim handles and labels if illegal label...
_lab, _hand = [], []
for label, handle in zip(labels, handles):
if isinstance(label, str) and label.startswith('_'):
_api.warn_external(f"The label {label!r} of {handle!r} starts "
"with '_'. It is thus excluded from the "
"legend.")
else:
_lab.append(label)
_hand.append(handle)
labels, handles = _lab, _hand

handles = list(handles)
if len(handles) < 2:
Expand Down Expand Up @@ -1228,8 +1216,6 @@ def _parse_legend_args(axs, *args, handles=None, labels=None, **kwargs):
*kwargs* with keywords handles and labels removed.

"""
log = logging.getLogger(__name__)

handlers = kwargs.get('handler_map')
extra_args = ()

Expand All @@ -1253,8 +1239,8 @@ def _parse_legend_args(axs, *args, handles=None, labels=None, **kwargs):
elif len(args) == 0:
handles, labels = _get_legend_handles_labels(axs, handlers)
if not handles:
log.warning(
"No artists with labels found to put in legend. Note that "
_api.warn_external(
"No artists with labels found to put in legend. Note that "
"artists whose label start with an underscore are ignored "
"when legend() is called with no argument.")

Expand Down
55 changes: 38 additions & 17 deletions lib/matplotlib/tests/test_legend.py
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Original file line number Diff line number Diff line change
Expand Up @@ -80,20 +80,40 @@ def test_various_labels():
ax.legend(numpoints=1, loc='best')


def test_legend_label_with_leading_underscore():
def test_legend_label_with_leading_underscore1():
"""
Test that artists with labels starting with an underscore are not added to
the legend, and that a warning is issued if one tries to add them
explicitly.
the legend when the legend method is called with no arguments, and that a
warning is issued if one tries to add them explicitly.
"""
fig, ax = plt.subplots()
line, = ax.plot([0, 1], label='_foo')
ax.plot([0, 1], label='_foo')
with pytest.warns(UserWarning,
match=r"starts with '_'.*excluded from the legend."):
legend = ax.legend(handles=[line])
match=r"artists whose label start with an underscore "
"are ignored"):
legend = ax.legend()
assert len(legend.legendHandles) == 0


def test_legend_label_with_leading_underscore2():
"""
Test that artists with labels starting with an underscore are added to the
legend when the legend method is called with arguments.
"""
fig, ax = plt.subplots()
lines = ax.plot([0, 1], label='_foo')
legend = ax.legend(handles=lines)
assert len(legend.legendHandles) == 1
legend = ax.legend(handles=lines, labels=["_foo"])
assert len(legend.legendHandles) == 1
legend = ax.legend(labels=["_foo"])
assert len(legend.legendHandles) == 1
legend = ax.legend(["_foo"])
assert len(legend.legendHandles) == 1
legend = ax.legend(lines, ["_foo"])
assert len(legend.legendHandles) == 1


@image_comparison(['legend_labels_first.png'], remove_text=True)
def test_labels_first():
# test labels to left of markers
Expand Down Expand Up @@ -512,9 +532,10 @@ def test_text_nohandler_warning():
"""Test that Text artists with labels raise a warning"""
fig, ax = plt.subplots()
ax.text(x=0, y=0, s="text", label="label")
with pytest.warns(UserWarning) as record:
with pytest.warns(UserWarning,
match="Legend does not support handles for .+ "
"instances"):
ax.legend()
assert len(record) == 1

# this should _not_ warn:
f, ax = plt.subplots()
Expand Down Expand Up @@ -546,7 +567,7 @@ def test_legend_title_empty():
# it comes back as an empty string, and that it is not
# visible:
fig, ax = plt.subplots()
ax.plot(range(10))
ax.plot(range(10), label="foo")
leg = ax.legend()
assert leg.get_title().get_text() == ""
assert not leg.get_title().get_visible()
Expand Down Expand Up @@ -579,7 +600,7 @@ def test_window_extent_cached_renderer():

def test_legend_title_fontprop_fontsize():
# test the title_fontsize kwarg
plt.plot(range(10))
plt.plot(range(10), label="foo")
with pytest.raises(ValueError):
plt.legend(title='Aardvark', title_fontsize=22,
title_fontproperties={'family': 'serif', 'size': 22})
Expand All @@ -590,27 +611,27 @@ def test_legend_title_fontprop_fontsize():

fig, axes = plt.subplots(2, 3, figsize=(10, 6))
axes = axes.flat
axes[0].plot(range(10))
axes[0].plot(range(10), label="foo")
leg0 = axes[0].legend(title='Aardvark', title_fontsize=22)
assert leg0.get_title().get_fontsize() == 22
axes[1].plot(range(10))
axes[1].plot(range(10), label="foo")
leg1 = axes[1].legend(title='Aardvark',
title_fontproperties={'family': 'serif', 'size': 22})
assert leg1.get_title().get_fontsize() == 22
axes[2].plot(range(10))
axes[2].plot(range(10), label="foo")
mpl.rcParams['legend.title_fontsize'] = None
leg2 = axes[2].legend(title='Aardvark',
title_fontproperties={'family': 'serif'})
assert leg2.get_title().get_fontsize() == mpl.rcParams['font.size']
axes[3].plot(range(10))
axes[3].plot(range(10), label="foo")
leg3 = axes[3].legend(title='Aardvark')
assert leg3.get_title().get_fontsize() == mpl.rcParams['font.size']
axes[4].plot(range(10))
axes[4].plot(range(10), label="foo")
mpl.rcParams['legend.title_fontsize'] = 20
leg4 = axes[4].legend(title='Aardvark',
title_fontproperties={'family': 'serif'})
assert leg4.get_title().get_fontsize() == 20
axes[5].plot(range(10))
axes[5].plot(range(10), label="foo")
leg5 = axes[5].legend(title='Aardvark')
assert leg5.get_title().get_fontsize() == 20

Expand Down Expand Up @@ -895,7 +916,7 @@ def test_legend_labelcolor_rcparam_markerfacecolor_short():


def test_get_set_draggable():
legend = plt.legend()
legend = plt.legend("foo")
assert not legend.get_draggable()
legend.set_draggable(True)
assert legend.get_draggable()
Expand Down