More code review changes and tests

Author: scottshambaugh

lib/mpl_toolkits/mplot3d/axes3d.py

@@ -107,6 +107,8 @@ def __init__(
         focal_length : float, default: None
             For a projection type of 'persp', the focal length of the virtual
             camera. Must be > 0. If None, defaults to 1.
+            For a projection type of 'ortho', must be set to either None
+            or infinity (numpy.inf). If None, defaults to infinity.
             The focal length can be computed from a desired Field Of View via
             the equation: focal_length = 1/tan(FOV/2)
 
@@ -1019,7 +1021,7 @@ def set_proj_type(self, proj_type, focal_length=None):
                 self._focal_length = focal_length
         elif proj_type == 'ortho':
             if focal_length not in (None, np.inf):
-                raise ValueError(f"focal_length = {focal_length} must be"
+                raise ValueError(f"focal_length = {focal_length} must be "
                                  f"None for proj_type = {proj_type}")
             self._focal_length = np.inf
 

lib/mpl_toolkits/tests/test_mplot3d.py

@@ -1036,6 +1036,15 @@ def test_unautoscale(axis, auto):
     np.testing.assert_array_equal(get_lim(), (-0.5, 0.5))
 
 
+def test_axes3d_focal_length_checks():
+    fig = plt.figure()
+    ax = fig.add_subplot(projection='3d')
+    with pytest.raises(ValueError):
+        ax.set_proj_type('persp', focal_length=0)
+    with pytest.raises(ValueError):
+        ax.set_proj_type('ortho', focal_length=1)
+
+
 @mpl3d_image_comparison(['axes3d_focal_length.png'], remove_text=False)
 def test_axes3d_focal_length():
     fig, axs = plt.subplots(1, 2, subplot_kw={'projection': '3d'})