How to overide custom node operator variables in the execution

Question

Related to the question here I wanted now to use the export custom node from the same addon. Considering that the invoke() function calls the file browser for setting the path the filename I would like to call the execution() function directly but by overriding the self.filepath variable. I've tried to follow the same trick as in the linked question, meaning:

override = {'node': bpy.data.node_groups['<node_group_name>'].nodes['VI CSV Export'], 'self.filepath':'<path_to_save_file>.csv'}
bpy.ops.node.csvexport(override, 'EXEC_DEFAULT')

But this complaints with the following error:

Error: Traceback (most recent call last):
  File "/ttsesm/blender-2.83.6-linux64/2.83/scripts/addons/vi-suite06/vi_operators.py", line 2200, in execute
    node = self.node
  File "/ttsesm/blender-2.83.6-linux64/2.83/scripts/modules/bpy_types.py", line 713, in __getattribute__
    return super().__getattribute__(attr)
AttributeError: 'NODE_OT_CSV' object has no attribute 'node'

location: /ttsesm/blender-2.83.6-linux64/2.83/scripts/modules/bpy/ops.py:199


Traceback (most recent call last):
  File "<blender_console>", line 1, in <module>
  File "/ttsesm/blender-2.83.6-linux64/2.83/scripts/modules/bpy/ops.py", line 199, in __call__
    ret = op_call(self.idname_py(), C_dict, kw, C_exec, C_undo)
RuntimeError: Error: Traceback (most recent call last):
  File "/ttsesm/blender-2.83.6-linux64/2.83/scripts/addons/vi-suite06/vi_operators.py", line 2200, in execute
    node = self.node
  File "/ttsesm/blender-2.83.6-linux64/2.83/scripts/modules/bpy_types.py", line 713, in __getattribute__
    return super().__getattribute__(attr)
AttributeError: 'NODE_OT_CSV' object has no attribute 'node'

location: /ttsesm/blender-2.83.6-linux64/2.83/scripts/modules/bpy/ops.py:199

My questions are why the node = self.node cannot be overridden and whether the way that I am overriding the self.filepath variable is the correct one.

Answer 1

self.node is set in invoke.

THe operator is designed to be invoked by pressing its button displayed on its node.

The operator defines

self.node = context.node

in its invoke method, and uses self.node in its execute method, and will hence not work unless invoked.

bpy.ops.foo.bar(override, 'INVOKE_DEFAULT', filepath=somefilepath)

IMO the simple fix is to edit the operator to use context.node as the node in place of self.node by placing

self.node = context.node

in the execute method also.

Alternatively return self.execute(context) from the invoke method if the value passed to self.filepath is a valid filepath and use

bpy.ops.foo.bar(override, 'INVOKE_DEFAULT', filepath=somefilepath)

to ensure it is invoked and node is set.

A note on overriding.

What you are passing in the override dictionary are context members, eg

override = {"foo" : "bar"}

then if passed as an override to the operator

context.foo == "bar"

is true within the operator.

The filepath is a property of the operator, not the context and is hence not going to do diddly squat if passed as part of the override. The operator (self) and context are not the same. Pass it to the operator as a keyword variable.

Fork it.

Finally, fork and make the changes, or suggest / request changes to the maintainer of the addon, so that it can be executed directly, or to find out if there are reasons why it cannot.