Merge pull request matplotlib#22883 from anntzer/tca

Tweak argument checking in tripcolor().

Author: oscargus

doc/api/next_api_changes/deprecations/22883-AL.rst

@@ -0,0 +1,3 @@
+Passing too many positional arguments to ``tripcolor``
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+... is now deprecated (extra arguments were previously silently ignored).

lib/matplotlib/tests/test_triangulation.py

@@ -242,7 +242,7 @@ def test_tripcolor_color():
     x = [-1, 0, 1, 0]
     y = [0, -1, 0, 1]
     fig, ax = plt.subplots()
-    with pytest.raises(ValueError, match="Missing color parameter"):
+    with pytest.raises(TypeError, match=r"tripcolor\(\) missing 1 required "):
         ax.tripcolor(x, y)
     with pytest.raises(ValueError, match="The length of C must match either"):
         ax.tripcolor(x, y, [1, 2, 3])
@@ -255,8 +255,8 @@ def test_tripcolor_color():
     with pytest.raises(ValueError,
                        match="'gouraud' .* at the points.* not at the faces"):
         ax.tripcolor(x, y, [1, 2], shading='gouraud')  # faces
-    with pytest.raises(ValueError,
-                       match=r"pass C positionally or facecolors via keyword"):
+    with pytest.raises(TypeError,
+                       match="positional.*'C'.*keyword-only.*'facecolors'"):
         ax.tripcolor(x, y, C=[1, 2, 3, 4])
 
     # smoke test for valid color specifications (via C or facecolors)
@@ -282,7 +282,7 @@ def test_tripcolor_warnings():
     C = [0.4, 0.5]
     fig, ax = plt.subplots()
     # additional parameters
-    with pytest.warns(UserWarning, match="Additional positional parameters"):
+    with pytest.warns(DeprecationWarning, match="Additional positional param"):
         ax.tripcolor(x, y, C, 'unused_positional')
     # facecolors takes precednced over C
     with pytest.warns(UserWarning, match="Positional parameter C .*no effect"):

lib/matplotlib/tri/tripcolor.py

@@ -79,12 +79,14 @@ def tripcolor(ax, *args, alpha=1.0, norm=None, cmap=None, vmin=None,
     else:
         # Color from positional parameter C
         if not args:
-            raise ValueError(
-                "Missing color parameter. Please pass C positionally or "
-                "facecolors via keyword")
+            raise TypeError(
+                "tripcolor() missing 1 required positional argument: 'C'; or "
+                "1 required keyword-only argument: 'facecolors'")
         elif len(args) > 1:
-            _api.warn_external(
-                "Additional positional parameters {args[1:]!r} are ignored")
+            _api.warn_deprecated(
+                "3.6", message=f"Additional positional parameters "
+                f"{args[1:]!r} are ignored; support for them is deprecated "
+                f"since %(since)s and will be removed %(removal)s")
         C = np.asarray(args[0])
         if len(C) == len(tri.x):
             # having this before the len(tri.triangles) comparison gives