Fail early when setting Text color to a non-colorlike.

Otherwise, the error is only raised when drawing the artist, which is
always confusing.  Also add a general `_check_color_like` mechanism and
use it for Line2D as well, instead of relying on a slightly strange
`if not is_color_like(): check_in_list(get_named_colors_mapping())`
call where the check_in_list *always* fails.

Author: anntzer

lib/matplotlib/colors.py

@@ -147,6 +147,15 @@ def is_color_like(c):
         return True
 
 
+def _check_color_like(**kwargs):
+    """
+    For each *key, value* pair in *kwargs*, check that *value* is color-like.
+    """
+    for k, v in kwargs.items():
+        if not is_color_like(v):
+            raise ValueError(f"{v!r} is not a valid value for {k}")
+
+
 def same_color(c1, c2):
     """
     Return whether the colors *c1* and *c2* are the same.

lib/matplotlib/lines.py

@@ -13,7 +13,6 @@
 from .artist import Artist, allow_rasterization
 from .cbook import (
     _to_unmasked_float_array, ls_mapper, ls_mapper_r, STEP_LOOKUP_MAP)
-from .colors import is_color_like, get_named_colors_mapping
 from .markers import MarkerStyle
 from .path import Path
 from .transforms import Bbox, BboxTransformTo, TransformedPath
@@ -1050,9 +1049,8 @@ def set_color(self, color):
         ----------
         color : color
         """
-        if not is_color_like(color) and color != 'auto':
-            _api.check_in_list(get_named_colors_mapping(),
-                               _print_supported_values=False, color=color)
+        if not cbook._str_equal(color, 'auto'):
+            mcolors._check_color_like(color=color)
         self._color = color
         self.stale = True
 

lib/matplotlib/tests/test_text.py

@@ -709,3 +709,8 @@ def test_update_mutate_input():
     t.update(inp)
     assert inp['fontproperties'] == cache['fontproperties']
     assert inp['bbox'] == cache['bbox']
+
+
+def test_invalid_color():
+    with pytest.raises(ValueError):
+        plt.figtext(.5, .5, "foo", c="foobar")

lib/matplotlib/text.py

@@ -934,6 +934,10 @@ def set_color(self, color):
         ----------
         color : color
         """
+        # "auto" is only supported by axisartist, but we can just let it error
+        # out at draw time for simplicity.
+        if not cbook._str_equal(color, "auto"):
+            mpl.colors._check_color_like(color=color)
         # Make sure it is hashable, or get_prop_tup will fail.
         try:
             hash(color)