Bugfix for loc legend validation

robrighter · robrighter · commit 51385ed5b2f7 · 2023-03-06T22:46:48.000-05:00
Co-authored-by: John Paul Jepko &lt;jpjepko@users.noreply.github.com&gt;
diff --git a/lib/matplotlib/legend.py b/lib/matplotlib/legend.py
@@ -23,6 +23,7 @@
 
 import itertools
 import logging
+import numbers
 import time
 
 import numpy as np
@@ -518,6 +519,8 @@ def val_or_rc(val, rc_name):
                 loc = 'upper right'
 
         # handle outside legends:
+        type_err_message = ("loc must be string, coordinate tuple or,"
+                            f" an integer 0-10, not {loc!r}")
         self._outside_loc = None
         if isinstance(loc, str):
             if loc.split()[0] == 'outside':
@@ -535,6 +538,18 @@ 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 isinstance(loc, tuple):
+            # 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(
diff --git a/lib/matplotlib/tests/test_legend.py b/lib/matplotlib/tests/test_legend.py
@@ -1219,3 +1219,71 @@ 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_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_string_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')
+    s = ("'wrong' is not a valid value for"
+         " loc; supported values are 'best', 'upper right', "
+         "'upper left', 'lower left', 'lower right', 'right',"
+         " 'center left', 'center right', 'lower center', "
+         "'upper center', 'center'")
+    with pytest.raises(ValueError, match=s):
+        ax.legend(loc='wrong')
