Blender v2.8 error: file export from new plugin

Question

For a blender v2.80 plugin I am developing I have to export a file generated from data available in the blender context. When I try to do the file export I obtain this exception:

from_object(...): currently only mesh objects are supported

which is given by the function bmesh.from_object()

I think it's because in the context I have some "illegal" element, but I am not able to understand which one. Can anyone help me?

I also attach the traceback of the error:

**Traceback (most recent call last):**

> File "C:\Users\Carlo\AppData\Roaming\Blender Foundation\Blender\2.80\scripts\addons\blenderfds28x\bl\menus.py", line 101, in execute
    fds_file = sc.to_fds(context=context, full=True)
  File "C:\Users\Carlo\AppData\Roaming\Blender Foundation\Blender\2.80\scripts\addons\blenderfds28x\lang.py", line 2030, in to_fds
    bodies.append(context.scene.collection.to_fds(context))
  File "C:\Users\Carlo\AppData\Roaming\Blender Foundation\Blender\2.80\scripts\addons\blenderfds28x\lang.py", line 2069, in to_fds
    bodies.extend(child.to_fds(context) for child in self.children)
  File "C:\Users\Carlo\AppData\Roaming\Blender Foundation\Blender\2.80\scripts\addons\blenderfds28x\lang.py", line 2069, in <genexpr>
    bodies.extend(child.to_fds(context) for child in self.children)
  File "C:\Users\Carlo\AppData\Roaming\Blender Foundation\Blender\2.80\scripts\addons\blenderfds28x\lang.py", line 2068, in to_fds
    bodies.extend(ob.to_fds(context) for ob in obs)
  File "C:\Users\Carlo\AppData\Roaming\Blender Foundation\Blender\2.80\scripts\addons\blenderfds28x\lang.py", line 2068, in <genexpr>
    bodies.extend(ob.to_fds(context) for ob in obs)
  File "C:\Users\Carlo\AppData\Roaming\Blender Foundation\Blender\2.80\scripts\addons\blenderfds28x\lang.py", line 1956, in to_fds
    return self.bf_namelist.to_fds(context)
  File "C:\Users\Carlo\AppData\Roaming\Blender Foundation\Blender\2.80\scripts\addons\blenderfds28x\types.py", line 244, in to_fds
    to_fds = p(self.element).to_fds(context)
  File "C:\Users\Carlo\AppData\Roaming\Blender Foundation\Blender\2.80\scripts\addons\blenderfds28x\lang.py", line 1229, in to_fds
    xbs, msg = geometry.to_fds.ob_to_xbs(context, ob, scale_length)
  File "C:\Users\Carlo\AppData\Roaming\Blender Foundation\Blender\2.80\scripts\addons\blenderfds28x\geometry\to_fds.py", line 136, in ob_to_xbs
    return _choice_to_xbs[ob.bf_xb](context, ob, scale_length)  # recalc
  File "C:\Users\Carlo\AppData\Roaming\Blender Foundation\Blender\2.80\scripts\addons\blenderfds28x\geometry\to_fds.py", line 58, in _ob_to_xbs_bbox
    xbs = list((utils.get_bbox_xbs(context, ob, scale_length, world=True),))
  File "C:\Users\Carlo\AppData\Roaming\Blender Foundation\Blender\2.80\scripts\addons\blenderfds28x\geometry\utils.py", line 78, in get_bbox_xbs
    bm = get_object_bmesh(context, ob, world=True)
  File "C:\Users\Carlo\AppData\Roaming\Blender Foundation\Blender\2.80\scripts\addons\blenderfds28x\geometry\utils.py", line 13, in get_object_bmesh
    bpy.ops.object.mode_set(mode="OBJECT")  # actualize
  File "F:\Tools\Blender\2.80\scripts\modules\bpy\ops.py", line 201, in __call__
    ret = op_call(self.idname_py(), None, kw)
RuntimeError: Operator bpy.ops.object.mode_set.poll() failed, context is incorrect

> location: F:\Tools\Blender\2.80\scripts\modules\bpy\ops.py:201

> location: F:\Tools\Blender\2.80\scripts\modules\bpy\ops.py:201
Error: Traceback (most recent call last):
  File "C:\Users\Carlo\AppData\Roaming\Blender Foundation\Blender\2.80\scripts\addons\blenderfds28x\bl\menus.py", line 101, in execute
    fds_file = sc.to_fds(context=context, full=True)
  File "C:\Users\Carlo\AppData\Roaming\Blender Foundation\Blender\2.80\scripts\addons\blenderfds28x\lang.py", line 2030, in to_fds
    bodies.append(context.scene.collection.to_fds(context))
  File "C:\Users\Carlo\AppData\Roaming\Blender Foundation\Blender\2.80\scripts\addons\blenderfds28x\lang.py", line 2069, in to_fds
    bodies.extend(child.to_fds(context) for child in self.children)
  File "C:\Users\Carlo\AppData\Roaming\Blender Foundation\Blender\2.80\scripts\addons\blenderfds28x\lang.py", line 2069, in <genexpr>
    bodies.extend(child.to_fds(context) for child in self.children)
  File "C:\Users\Carlo\AppData\Roaming\Blender Foundation\Blender\2.80\scripts\addons\blenderfds28x\lang.py", line 2068, in to_fds
    bodies.extend(ob.to_fds(context) for ob in ... truncated

Answer 1

The "only mesh objects are supported" would indicate that the object you are trying to get mesh data from is not a mesh object.

If you are looping through the selected objects, test that the object is a mesh object before converting.

for obj in bpy.context.selected_objects:
    if obj.type == 'MESH':
        bm.from_object(obj, context.view_layer.depsgraph)

You may also want to consider that bmesh is intended for editing mesh data, you can read the mesh data without converting it to bmesh.

for obj in bpy.context.selected_objects:
    if obj.type == 'MESH':
        for v in obj.data.vertices:
            print(v.co)
        for e in obj.data.edges:
            print(e.index)
        for f in obj.data.polygons:
            print(f.index)