Range question type default should start at 0 and not 1

[Zachary-Sutherby]

From XLSForm spec, the Range question type by default should start at 0 and not 1.

pyxform default has "start" set to 1:

pyxform/pyxform/xls2json.py

Line 160 in 8288ba5

defaults = {"start": "1", "end": "10", "step": "1"}

[lognaturel]

Thanks for reporting! A PR would be welcome or we'll take it on soon.

[Zachary-Sutherby]

@lognaturel Thank you! PR submitted, unfortunately it looks like I can't set reviewers on the PR.

[lindsay-stevens]

@lognaturel some background:

• The feature design ticket and implementation PR (July 2017) nominated start=1 as the default, including in tests.
• The XLSForm.org docs PR (Feb 2018) doesn't say why it was documented as start=0 instead.
• The ODK spec and XForms spec and XLSForm.org template don't specify default values.
• The ODK docs and example form with all question types show examples using start=1 or assuming that default (i.e. the 5-star scale wiith appearance=rating and end=5 shows 5 stars).
• Since at least 2022 the Kobo docs show start=1 as an example but it the UI uses start=0 as the default (seen briefly in docs page video, and this kpi feature PR).
• Since at least 2019 the ESRI docs say the default is start=0.

Currently the range parameters are not required, so a change to the defaults would be not be backwards compatible for ODK users with forms using range without specifying a start value. I'm not sure about other libraries or form builders (besides kpi). If the default start value is changed then probably the above ODK docs should be updated.

In my opinion the default start=1 is more intuitive, considering that with the other defaults end=10 and step=1 it results in 10 ticks e.g. for a "rating on a scale out of 10" kind of question; whereas start=0 would give a default of 11 ticks.

[lognaturel]

Apologies for my hasty response, it seemed like a straightforward mismatch to redress but I now see it's not, @lindsay-stevens, thanks as always for the careful archaeology.

Given that we are really careful not to break compatibility and that this default has been as it is for over 8 years, it makes more sense to update docs instead. @Zachary-Sutherby, does that seem reasonable?

[tiritea]

...but it the UI uses start=0 as the default (seen briefly in docs page video...

Correct. Kobo defaults to start=0, end=10, step=1 when you add a range question in Kobo Formbuilder, but dont otherwise customize anything. These same values will, obviously, subsequently appear in the default resulting XForm generated by pyxform; that is, unless the form writer chooses to explicitly change them.

As Lindsay notes, the Kobo docs do appear to (override) this with a stated start=1, end=5, step=1 in most of our online examples.

All that said, I dont think we're particularly precious about this: the Kobo Formbuilder is already overriding pyxform's (incorrect?) defacto start=1 with XLSForm's defacto start=0... But it is still probably worth making form writers aware of the diff.

FWIW, I agree this could be considered a breaking change to folks with an existing XLSForm (that is, one not generated from Kobo's Formbuilder); if they re-deploy their XLSForm form they'll end up with a different XForm, one that has effectively added a (valid) 0 option to all their range questions.