variable_user_pre_initialize_extension is not valid when left empty

[charredchar]

I receive an error stating I need to home when selecting a file to print if I do not home the printer before selecting the file.
Since I use Klicky-00 I have my homing routine within my start gcode which is just after the MMU_START_SETUP in my slicer. But the printer does not get that far into the start gcode before triggering this error. I can not move this homing before the MMU_START_SETUP as the rest of my start macro depends on the specific homing used within the macro.
Removing MMU_START_SETUP from my start gcode in the slicer allows the printer to start without an issue except for the fact nothing gets passed to HH.

klippy.log

[moggieuk]

I you sure you are not calling something extra in the MMU_START_SETUP? E.g. is

variable_user_pre_initialize_extension      : ""

set to anything?

The MMU_START_SETUP should not attempt to move the toolhead during setup (unless an error occurs and even then it will just report a warning).

[charredchar]

The only option I currently have for MMU_START_SETUP is INITIAL_TOOL since I do not have the other options set up yet.

I originally had G28 in the variable_user_pre_initialize_extension option (as it is there by default) but it was causing a second unneeded homing as I have one near the start of my start gcode.

I attempted to remove it (leaving it empty as your example) but I would receive a Klipper error;
Option 'variable_user_pre_initialize_extension' in section 'gcode_macro _MMU_SOFTWARE_VARS' is not a valid literal: unexpected EOF while parsing (, line 0)

So I changed it to M117 just to have something there and the error of not having anything there went away.

And while I was typing this out I decided to test a little more... I found the issue and I am a little annoyed at the cause. 😅
For some reason SuperSlicer added a move before any of my start gcode. I've never seen this before using an MMU and I've seen this error happen more than once so I (falsely) assumed it was MMU related and not my slicer. Sorry, I should have check my gcode file first. I will continue to troubleshoot this with SuperSlicer.
But I do want to change this issue to the semi-related error with variable_user_pre_initialize_extension being empty noted above. Having M117 in there is kind of more of a hack than anything, it should allow for it to be empty.

[moggieuk]

This isn't actually a bug, but rather a limitation of jinja templating and evaluation. I suspect you are still running under Python2. In this version (which has been deprecated for 3 years now) you cannot set to a double quoted string. I know that a single quoted string will work like:

variable_user_pre_initialize_extension      : ''

Because it is a "feature" of python there is nothing I can do to support double quote on Python 2.

Re Slicer issue: SuperSlicer does have quirks -- one reason I stick with PrusaSlicer (they are annoyingly slow at taking PRs and updates but there QA is good). But thanks for the info!

If you can validate the single quote and Python2 setup then I can close out this issue.