**System Information**
Linux Mint 17.2 64 bit and Windows 7 64 bit
GeForce 540M GT
**Blender Version**
Broken: since 2.73 (up to to 2.77 rc1)
Worked: 2.72a
**Short description of error**
Mesh.calc_smooth_groups() doesn't properly generate smooth groups. It always generates as many smooth groups as there are faces in the mesh.
**Exact steps for others to reproduce the error**
Attached blend file contains a plane with 4 faces. The edges of one of the faces are marked as sharp.
Following code:
obj = bpy.data.objects['Plane']
me = obj.to_mesh(bpy.context.scene, True, 'PREVIEW')
(sg, nsg) = me.calc_smooth_groups()
print(sg)
{F286527} (script contained in the text file "test", just run script)
Output on blender 2.72a or older: (1, 2, 1, 1)
Output on blender 2.73 or newer: (1, 2, 3, 4)