Bad .json file format is detected (Cando upload)

[ecx2093]

I am using cadnano ver 2.5.1.11 and I am running into some issues when I upload my .json file to the Cando modelling server. I get the following error:

Bad .json file format is detected in ‘tutorial_resave.json’. Or no dsDNA or strand crossovers exist. Please check your file format.

So I went to the tutorials section on the Cando website and downloaded their .json file for a simple two helix bundle. Uploading this to the Cando server works fine and I get the results back. HOWEVER when i download the .json, open it with cadnano, resave it under a new file name, and then upload to the Cando server, I get the bad .json error back.

Could there be some problem with saving to .json that now renders the file incompatible with Cando? I swear I was able to upload .json files from Cadnano to Cando about a year ago, but that was probably a different version of cadnano.

[polyhdron]

Hi, I ran into the same problem. Any solution or workaround yet?
I suppose the new .json file format is not supported by CanDo. Is there a way to convert it back to the old .json format? (In the documentation under 'Scripting' I saw the 'Export to Legacy Format' section with TK...)
Cadnano 2.0 crashes when I try to open the file, same for cadnanoSQ 0.2.4.
Thanks a lot!

[Akodiat]

It's possible to write a script to load the file, then use writeToFile() with legacy=True to write it in legacy format.

This works for cadnano 2.5.1, at least for the simple design I just tested:

import sys
import cadnano
from cadnano.document import Document

app = cadnano.app()
doc = app.document = Document()

filename = sys.argv[1]
    
doc.readFile(filename)
doc.writeToFile(filename=('converted_'+filename), legacy=True)

[polyhdron]

Thanks, it worked!
In the meantime I also found the script here:
https://github.com/cadnano/cadnano2.5/tree/master/misc/examples/02_export_legacy