Problem with template in Kobo Driver

[Terisa de morgan]

I've got this template for subtitle in the Kobo Driver, and it has been working till now (it works indeed when I send the books):

program:
	pags = field ("#pag");
	subDes = field ("#subd_enc");
	miVal = field ("#mi_val");
     mediaStar = field ("#media_s");
	
	subTitle = pags ;
	if (subDes)
	then
		subTitle = subTitle & "-" & subDes
	fi;

	if (miVal > 0)
	then
		subTitle = subTitle & " (" & rating_to_stars(miVal, 0);
		if (fractional_part (miVal) !=# 0)
		then
			subTitle = subTitle & "½" & ")"
		else
			subTitle = subTitle & ")"
		fi
	fi;
	subTitle

Now, just out of the blue, I try to modify another configuration in the driver and I get this message:

Spoiler:

calibre, version 8.5.0
ERROR: Invalid template for Subtitle: <p>The template "program:
pags = field ("#pag");
subDes = field ("#subd_enc");
miVal = field ("#mi_val");
mediaStar = field ("#media_s");

subTitle = pags ;
if (subDes)
then
subTitle = subTitle & "-" & subDes
fi;

if (miVal > 0)
then
subTitle = subTitle & " (" & rating_to_stars(miVal, 0);
if (fractional_part (miVal) !=# 0)
then
subTitle = subTitle & "½" & ")"
else
subTitle = subTitle & ")"
fi
fi;
subTitle" is invalid:<br>The rating must be a number between 0 and 5

What has changed? As I haven't touched it since the Kobo Extended driver was deprecated.
Additional info: I see the json file has as date: Jun 5, 2025, that I added another collection to ignore, and the change was fine. I've been up to date with 8 version, so I would be running the latest release at that moment. And, furthermore, it has just worked when I've sent books to the device.

[chaley]

What changed is that from 11 May the kobo driver now checks templates. Unfortunately it doesn't have a real book so it uses "fake" metadata. This can cause the problem you are seeing.

I think I will take out the validations. They seem to cause more problems than help.

[chaley]

I've submitted a fix to Kovid.

The specific problem is that the fake metadata for your rating column is text, which can't convert to a number. You can work around the problem until my fix is released by changing

miVal = field ("#mi_val");

to

miVal = format_number($#mi_val, 'd');

The format_number() function changes invalid text to the empty string, which is interpreted as 0 in a numeric context.

[Terisa de morgan]

Originally Posted by chaley

What changed is that from 11 May the kobo driver now checks templates. Unfortunately it doesn't have a real book so it uses "fake" metadata. This can cause the problem you are seeing.

I think I will take out the validations. They seem to cause more problems than help.

If fake metadata doesn't take into account real types... yes, I see it

[Terisa de morgan]

Originally Posted by chaley

I've submitted a fix to Kovid.

The specific problem is that the fake metadata for your rating column is text, which can't convert to a number. You can work around the problem until my fix is released by changing

miVal = field ("#mi_val");

to

miVal = format_number($#mi_val, 'd');

The format_number() function changes invalid text to the empty string, which is interpreted as 0 in a numeric context.

Thank you, I've changed it and it works Anyway, I'd already solved my problem, as it was a small change, and notepad++ over json complains less

[chaley]

Originally Posted by Terisa de morgan

If fake metadata doesn't take into account real types... yes, I see it

The changes I submitted solve exactly this problem, constructing a Metadata object by looking at the types of the fields in the database. I used the same solution as I did for the Template Tester some years ago. Once the change is accepted, if the template works in the template tester called from the Kobo driver then it will also work when the driver does validatation.

A side benefit: constructing a "model" metadata instance, one with all fields defined and set to plausible values, is now done by the API function get_model_metadata_instance() in calibre.ebooks.metadata.base.

[Terisa de morgan]

Thank you, I'll test the original templatge again when the changes are in the official realese.