Rewrite Triangulation.get_from_args_and_kwargs to make parameter parsing testable

Author: timhoffm

lib/matplotlib/tests/test_triangulation.py

@@ -12,6 +12,52 @@
 from matplotlib.testing.decorators import image_comparison, check_figures_equal
 
 
+x = [-1, 0, 1, 0]
+y = [0, -1, 0, 1]
+triangles = [[0, 1, 2], [0, 2, 3]]
+mask = [False, True]
+
+
+@pytest.mark.parametrize('args, kwargs, expected', [
+    ([x, y], {}, [x, y, None, None]),
+    ([x, y, triangles], {}, [x, y, triangles, None]),
+    ([x, y], dict(triangles=triangles), [x, y, triangles, None]),
+    ([x, y], dict(mask=mask), [x, y, None, mask]),
+    ([x, y, triangles], dict(mask=mask), [x, y, triangles, mask]),
+    ([x, y], dict(triangles=triangles, mask=mask), [x, y, triangles, mask]),
+])
+def test_extract_triangulation_params(args, kwargs, expected):
+    other_args = [1, 2]
+    other_kwargs = {'a': 3, 'b': '4'}
+    x_, y_, triangles_, mask_, args_, kwargs_ = \
+        mtri.Triangulation._extract_triangulation_params(
+            args + other_args, {**kwargs, **other_kwargs})
+    x, y, triangles, mask = expected
+    assert x_ is x
+    assert y_ is y
+    assert_array_equal(triangles_, triangles)
+    assert mask_ is mask
+    assert args_ == other_args
+    assert kwargs_ == other_kwargs
+
+
+def test_extract_triangulation_positional_mask():
+    global x, y, triangles, mask
+    # mask cannot be passed positionally
+    x_, y_, triangles_, mask_, args_, kwargs_ = \
+        mtri.Triangulation._extract_triangulation_params(x, y, triangles, mask)
+    assert mask_ is None
+    assert args_ == [mask]
+    # the positional mask has to be catched downstream because this must pass
+    # unknown args through
+
+
+del x
+del y
+del triangles
+del mask
+
+
 def test_delaunay():
     # No duplicate points, regular grid.
     nx = 5

lib/matplotlib/tri/triangulation.py

@@ -136,34 +136,34 @@ def get_from_args_and_kwargs(*args, **kwargs):
         if isinstance(args[0], Triangulation):
             triangulation, *args = args
         else:
-            x, y, *args = args
-
-            # Check triangles in kwargs then args.
-            triangles = kwargs.pop('triangles', None)
-            from_args = False
-            if triangles is None and args:
-                triangles = args[0]
-                from_args = True
-
-            if triangles is not None:
-                try:
-                    triangles = np.asarray(triangles, dtype=np.int32)
-                except ValueError:
-                    triangles = None
-
-            if triangles is not None and (triangles.ndim != 2 or
-                                          triangles.shape[1] != 3):
-                triangles = None
-
-            if triangles is not None and from_args:
-                args = args[1:]  # Consumed first item in args.
-
-            # Check for mask in kwargs.
-            mask = kwargs.pop('mask', None)
-
+            x, y, triangles, mask, args, kwargs = \
+                Triangulation._extract_triangulation_params(args, kwargs)
             triangulation = Triangulation(x, y, triangles, mask)
         return triangulation, args, kwargs
 
+    @staticmethod
+    def _extract_triangulation_params(args, kwargs):
+        x, y, *args = args
+        # Check triangles in kwargs then args.
+        triangles = kwargs.pop('triangles', None)
+        from_args = False
+        if triangles is None and args:
+            triangles = args[0]
+            from_args = True
+        if triangles is not None:
+            try:
+                triangles = np.asarray(triangles, dtype=np.int32)
+            except ValueError:
+                triangles = None
+        if triangles is not None and (triangles.ndim != 2 or
+                                      triangles.shape[1] != 3):
+            triangles = None
+        if triangles is not None and from_args:
+            args = args[1:]  # Consumed first item in args.
+        # Check for mask in kwargs.
+        mask = kwargs.pop('mask', None)
+        return x, y, triangles, mask, args, kwargs
+
     def get_trifinder(self):
         """
         Return the default `matplotlib.tri.TriFinder` of this