Bugfix for loc legend validation

Co-authored-by: John Paul Jepko <[email protected]>

Author: robrighter

lib/matplotlib/legend.py

@@ -23,6 +23,7 @@
 
 import itertools
 import logging
+import numbers
 import time
 
 import numpy as np
@@ -517,6 +518,9 @@ def val_or_rc(val, rc_name):
             if not self.isaxes and loc in [0, 'best']:
                 loc = 'upper right'
 
+        type_err_message = ("loc must be string, coordinate tuple, or"
+                            f" an integer 0-10, not {loc!r}")
+
         # handle outside legends:
         self._outside_loc = None
         if isinstance(loc, str):
@@ -535,6 +539,19 @@ def val_or_rc(val, rc_name):
                     loc = locs[0] + ' ' + locs[1]
             # check that loc is in acceptable strings
             loc = _api.check_getitem(self.codes, loc=loc)
+        elif np.iterable(loc):
+            # coerce iterable into tuple
+            loc = tuple(loc)
+            # validate the tuple represents Real coordinates
+            if len(loc) != 2 or not all(isinstance(e, numbers.Real) for e in loc):
+                raise ValueError(type_err_message)
+        elif isinstance(loc, int):
+            # validate the integer represents a string numeric value
+            if loc < 0 or loc > 10:
+                raise ValueError(type_err_message)
+        else:
+            # all other cases are invalid values of loc
+            raise ValueError(type_err_message)
 
         if self.isaxes and self._outside_loc:
             raise ValueError(

lib/matplotlib/tests/test_legend.py

@@ -1219,3 +1219,79 @@ def test_ncol_ncols(fig_test, fig_ref):
     ncols = 3
     fig_test.legend(strings, ncol=ncols)
     fig_ref.legend(strings, ncols=ncols)
+
+
+def test_loc_invalid_tuple_exception():
+    # check that exception is raised if the loc arg
+    # of legend is not a 2-tuple of numbers
+    fig, ax = plt.subplots()
+    with pytest.raises(ValueError, match=('loc must be string, coordinate '
+                       'tuple, or an integer 0-10, not \\(1.1,\\)')):
+        ax.legend(loc=(1.1, ))
+
+    with pytest.raises(ValueError, match=('loc must be string, coordinate '
+                       'tuple, or an integer 0-10, not \\(0.481, 0.4227, 0.4523\\)')):
+        ax.legend(loc=(0.481, 0.4227, 0.4523))
+
+    with pytest.raises(ValueError, match=('loc must be string, coordinate '
+                       'tuple, or an integer 0-10, not \\(0.481, \'go blue\'\\)')):
+        ax.legend(loc=(0.481, "go blue"))
+
+
+def test_loc_valid_tuple():
+    fig, ax = plt.subplots()
+    ax.legend(loc=(0.481, 0.442))
+    ax.legend(loc=(1, 2))
+
+
+def test_loc_valid_list():
+    fig, ax = plt.subplots()
+    ax.legend(loc=[0.481, 0.442])
+    ax.legend(loc=[1, 2])
+
+
+def test_loc_invalid_list_exception():
+    fig, ax = plt.subplots()
+    with pytest.raises(ValueError, match=('loc must be string, coordinate '
+                       'tuple, or an integer 0-10, not \\[1.1, 2.2, 3.3\\]')):
+        ax.legend(loc=[1.1, 2.2, 3.3])
+
+
+def test_loc_invalid_type():
+    fig, ax = plt.subplots()
+    with pytest.raises(ValueError, match=("loc must be string, coordinate "
+                       "tuple, or an integer 0-10, not {'not': True}")):
+        ax.legend(loc={'not': True})
+
+
+def test_loc_validation_numeric_value():
+    fig, ax = plt.subplots()
+    ax.legend(loc=0)
+    ax.legend(loc=1)
+    ax.legend(loc=5)
+    ax.legend(loc=10)
+    with pytest.raises(ValueError, match=('loc must be string, coordinate '
+                       'tuple, or an integer 0-10, not 11')):
+        ax.legend(loc=11)
+
+    with pytest.raises(ValueError, match=('loc must be string, coordinate '
+                       'tuple, or an integer 0-10, not -1')):
+        ax.legend(loc=-1)
+
+
+def test_loc_validation_string_value():
+    fig, ax = plt.subplots()
+    ax.legend(loc='best')
+    ax.legend(loc='upper right')
+    ax.legend(loc='best')
+    ax.legend(loc='upper right')
+    ax.legend(loc='upper left')
+    ax.legend(loc='lower left')
+    ax.legend(loc='lower right')
+    ax.legend(loc='right')
+    ax.legend(loc='center left')
+    ax.legend(loc='center right')
+    ax.legend(loc='lower center')
+    ax.legend(loc='upper center')
+    with pytest.raises(ValueError, match="'wrong' is not a valid value for"):
+        ax.legend(loc='wrong')