Fix Line3DCollection with autolim=True for lines of different lengths (matplotlib#30423)

* Fix Line3DCollection with autolim=True for lines of different lengths

When using Line3DCollection with autolim=True, the code was trying to
convert ragged arrays (lines with different numbers of points) directly
to a numpy array, which would fail. This fix extracts coordinates
separately to avoid the issue.

Fixes matplotlib#30418

* fix lint

* fix lint

* Add test for Line3DCollection with autolim=True and ragged arrays

* move test

* Update lib/mpl_toolkits/mplot3d/tests/test_axes3d.py

Co-authored-by: Elliott Sales de Andrade <quantum.analyst@gmail.com>

* Update lib/mpl_toolkits/mplot3d/tests/test_axes3d.py

Co-authored-by: Elliott Sales de Andrade <quantum.analyst@gmail.com>

---------

Co-authored-by: Elliott Sales de Andrade <quantum.analyst@gmail.com>

Author: MengAiDev

lib/mpl_toolkits/mplot3d/axes3d.py

@@ -2890,8 +2890,10 @@ def add_collection3d(self, col, zs=0, zdir='z', autolim=True, *,
 
         if autolim:
             if isinstance(col, art3d.Line3DCollection):
-                self.auto_scale_xyz(*np.array(col._segments3d).transpose(),
-                                    had_data=had_data)
+                # Handle ragged arrays by extracting coordinates separately
+                all_points = np.concatenate(col._segments3d)
+                self.auto_scale_xyz(all_points[:, 0], all_points[:, 1],
+                                    all_points[:, 2], had_data=had_data)
             elif isinstance(col, art3d.Poly3DCollection):
                 self.auto_scale_xyz(col._faces[..., 0],
                                     col._faces[..., 1],

lib/mpl_toolkits/mplot3d/tests/test_axes3d.py

@@ -2689,3 +2689,25 @@ def test_ndarray_color_kwargs_value_error():
     ax = fig.add_subplot(111, projection='3d')
     ax.scatter(1, 0, 0, color=np.array([0, 0, 0, 1]))
     fig.canvas.draw()
+
+
+def test_line3dcollection_autolim_ragged():
+    """Test Line3DCollection with autolim=True and lines of different lengths."""
+    fig = plt.figure()
+    ax = fig.add_subplot(projection='3d')
+
+    # Create lines with different numbers of points (ragged arrays)
+    edges = [
+        [(0, 0, 0), (1, 1, 1), (2, 2, 2)],  # 3 points
+        [(0, 1, 0), (1, 2, 1)],             # 2 points
+        [(1, 0, 1), (2, 1, 2), (3, 2, 3), (4, 3, 4)]  # 4 points
+    ]
+
+    # This should not raise an exception.
+    collections = ax.add_collection3d(art3d.Line3DCollection(edges), autolim=True)
+
+    # Check that limits were computed correctly with margins
+    # The limits should include all points with default margins
+    assert np.allclose(ax.get_xlim3d(), (-0.08333333333333333, 4.083333333333333))
+    assert np.allclose(ax.get_ylim3d(), (-0.0625, 3.0625))
+    assert np.allclose(ax.get_zlim3d(), (-0.08333333333333333, 4.083333333333333))