Add validation for fontstretch

oscargus · oscargus · commit 63eba3b87daa · 2022-03-04T20:19:09.000+01:00
diff --git a/lib/matplotlib/rcsetup.py b/lib/matplotlib/rcsetup.py
@@ -387,6 +387,20 @@ def validate_fontweight(s):
         raise ValueError(f'{s} is not a valid font weight.') from e
 
 
+def validate_fontstretch(s):
+    stretchvalues = [
+        'ultra-condensed', 'extra-condensed', 'condensed', 'semi-condensed',
+        'normal', 'semi-expanded', 'expanded', 'extra-expanded',
+        'ultra-expanded']
+    # Note: Historically, stretchvalues have been case-sensitive in Matplotlib
+    if s in stretchvalues:
+        return s
+    try:
+        return int(s)
+    except (ValueError, TypeError) as e:
+        raise ValueError(f'{s} is not a valid font stretch.') from e
+
+
 def validate_font_properties(s):
     parse_fontconfig_pattern(s)
     return s
@@ -900,7 +914,7 @@ def _convert_validator_spec(key, conv):
     "font.family":     validate_stringlist,  # used by text object
     "font.style":      validate_string,
     "font.variant":    validate_string,
-    "font.stretch":    validate_string,
+    "font.stretch":    validate_fontstretch,
     "font.weight":     validate_fontweight,
     "font.size":       validate_float,  # Base font size in points
     "font.serif":      validate_stringlist,
diff --git a/lib/matplotlib/tests/test_rcparams.py b/lib/matplotlib/tests/test_rcparams.py
@@ -20,6 +20,7 @@
     _validate_color_or_linecolor,
     validate_cycler,
     validate_float,
+    validate_fontstretch,
     validate_fontweight,
     validate_hatch,
     validate_hist_bins,
@@ -469,6 +470,26 @@ def test_validate_fontweight(weight, parsed_weight):
         assert validate_fontweight(weight) == parsed_weight
 
 
+@pytest.mark.parametrize('stretch, parsed_stretch', [
+    ('expanded', 'expanded'),
+    ('EXPANDED', ValueError),  # stretch is case-sensitive
+    (100, 100),
+    ('100', 100),
+    (np.array(100), 100),
+    # fractional fontweights are not defined. This should actually raise a
+    # ValueError, but historically did not.
+    (20.6, 20),
+    ('20.6', ValueError),
+    ([100], ValueError),
+])
+def test_validate_fontstretch(stretch, parsed_stretch):
+    if parsed_stretch is ValueError:
+        with pytest.raises(ValueError):
+            validate_fontstretch(stretch)
+    else:
+        assert validate_fontstretch(stretch) == parsed_stretch
+
+
 def test_keymaps():
     key_list = [k for k in mpl.rcParams if 'keymap' in k]
     for k in key_list:
