Ensure that Path.arc works for any full circle.

QuLogic · QuLogic · commit 5f5ecb9c0ed2 · 2017-08-05T18:36:46.000-04:00
Depending on the inputs, the range may get squashed down to ~0 when trying to remove extra 2pi revolutions. Fixes #8992.
diff --git a/lib/matplotlib/path.py b/lib/matplotlib/path.py
@@ -872,6 +872,9 @@ def arc(cls, theta1, theta2, n=None, is_wedge=False):
         eta1 = np.arctan2(np.sin(theta1), np.cos(theta1))
         eta2 = np.arctan2(np.sin(theta2), np.cos(theta2))
         eta2 -= twopi * np.floor((eta2 - eta1) / twopi)
+        # Ensure 2pi range is not flattened to 0 due to floating-point errors.
+        if theta2 - theta1 > np.pi and eta2 - eta1 < np.pi:
+            eta2 += twopi
 
         # number of curve segments to make
         if n is None:
diff --git a/lib/matplotlib/tests/test_path.py b/lib/matplotlib/tests/test_path.py
@@ -205,3 +205,15 @@ def test_path_deepcopy():
     path2 = Path(verts, codes)
     copy.deepcopy(path1)
     copy.deepcopy(path2)
+
+
+@pytest.mark.parametrize('offset', range(-720, 361, 45))
+def test_full_arc(offset):
+    low = offset
+    high = 360 + offset
+
+    path = Path.arc(low, high)
+    mins = np.min(path.vertices, axis=0)
+    maxs = np.max(path.vertices, axis=0)
+    np.testing.assert_allclose(mins, -1)
+    assert np.allclose(maxs, 1)
