Option for cross-compatibility

[BrendanParmer]

• Add an option to generate code for both Blender pre-4.0 and 4.0+ NodeTree interfaces

[BrendanParmer]

Blender 4.1 introduces some breaking changes with NodeSockets that complicates things a little bit here.

In previous versions of Blender it was necessary to use the index of the node socket for setting defaults or linking sockets together, usually because the node would have multiple sockets of the same name, but different types. This was annoying and somewhat illegible.

In Blender 4.0, they introduced changes intended to make string lookups the primary way of accessing node sockets, but indexing was kept backwards compatible.

With Blender 4.1, several nodes now use dynamic declaration, and sockets no longer necessarily have the same indices as in previous versions, and previous scripts aren't forward compatible if using indexing.

Indices aren't reliable going from 4.1 to previous versions. Really, string lookups are necessary in both cases, only Blender will handle it for us post-4.0, getting us something like

if bpy.app.version < (4, 0, 0):
    for (key, socket) in node.[in/out]puts.items():
        if key == name and socket.type == type:
            #use this socket
else:
    if socket.enabled:
        # just use regular string lookup
    # otherwise don't generate

Defaults for unavailable sockets wouldn't be forwards-compatible, but this seems like an unlikely use case. NodeToPython probably shouldn't even be generating code for these unavailable sockets anyways

[Vollkornaffe]

Is the plan to have NodeToPython generate a top-level branch and then entirely separate generation code for different versions, or could it be possible to generate a "mostly shared" script that branches only where needed?

[BrendanParmer]

The first option's definitely easier, but NodeToPython's already verbose enough right now. Only branching where needed is my preference.

As a heads up, I plan on deprecating support for Blender versions earlier than 4.2 (oldest LTS) in the next release (earlier versions of NTP will always be available for download), so the original stuff in this issue about the NodeTree interfaces won't apply anymore. I do have cross-compatibility in general as a long-term goal, though there's lower hanging fruit I've been wanting to get to first. If there's interest from the community I'm happy to move it up my priority list, though