Loading Error: 'TypeError: Cannot set property 'textContent' of null'

[mdestaubin]

Description

The users forms were reportedly working properly until Nov 5th, when some of their forms began showing the loading error: 'TypeError: Cannot set property 'textContent' of null'

Steps to Reproduce

1. Upload XLSForm from conversation https://app.intercom.io/a/apps/s6hn3a8q/inbox/inbox/2698693/conversations/19407773139 to the HHI server.
2. Try to open or preview the form.

Expected behavior

The form should open or be previewed properly with no loading errors.

Actual behavior

Loading Error: 'TypeError: Cannot set property 'textContent' of null' pops up.

Additional details

[tinok]

Congrats on your first bug report @mdestaubin 🙌 🕺

[magicznyleszek]

@jnm do you think this can have something to do with Martijn removing jQuery from Enketo? I remember he mentioned he had bugs because jQuery handles not found nodes behind the scenes.

[jnm]

@magicznyleszek, maybe. I tried this Multilingual_V_5_03.xls form and a different error appears in Firefox: TypeError: i[0].querySelector(...) is null. Chrome still shows TypeError: Cannot set property 'textContent' of null, though.

In any event, this bug needs to be filed against Enketo Express: https://github.com/enketo/enketo-express/issues

[jnm]

With the handy-dandy browser developer tools, I was able to figure out that things were getting hung up around this part of the form:

type	name
begin_repeat	group_csv
calculate	ex_date
calculate	ex_depatred
calculate	ex_staff
calculate	ex_order_no
calculate	ex_progrmm_loc
calculate	all_pujas_date
calculate	ex_lang
calculate	ex_name
calculate	ex_cc
calculate	ex_prasad_name
calculate	ex_adress
calculate	ex_zip_city
calculate	ex_country
calculate	ex_star
calculate	all_pujas_name
calculate	all_pujas_date_001
calculate	ex_notes
calculate	ex_mail
calculate	ex_phone
calculate	ex_birthdates
end_repeat

A minimal form to reproduce the problem needs only:

type	name	label
begin_repeat	mysterious_repeat	mysterious repeat
end_repeat

@magicznyleszek, I'll ask you to try your hand at this kind of troubleshooting in the future.

@tinok, is there a valid reason for someone to have a repeating group filled only with calculate questions? If not, can we tell the user that we appreciate the bug report, while advising them that their form design is actually broken? (@mdestaubin, this is what we need to know for you to respond to the user)

[jnm]

If my understanding of kobotoolbox/enketo-express#1112 is correct, this should be fixed by rejecting forms with empty repeating groups as invalid. I mentioned this particular manifestation of the issue to Martijn at enketo/enketo-validate#38.