Conditional logic can cause an Orbeon form error

[robshaffbbc]

To recreate:

1. In the form editor make a form with two controls: one text field and one Boolean check box.
2. In the basic settings tab for the check box set the name to "acontrol"
3. In the formulas tab for the text field under Visibility enter $acontrol = 'true'
4. Save + Publish the form in the form editor
5. In the form runner tick the check box and save the form.
6. Reload the form and a form error will prevent the form runner from loading the form for editing.

Notes:

• Comparing the boolean value of the checkbox to any string seems to do this.
• Changing Visibility to $acontrol = true() works fine.

[robshaffbbc]

May or may not be related but putting $variable in the calculated value field when $variable is not defined produces a generic form error when running the form.

[ebruchez]

This is kind of by design: the idea is that such errors taking place during page initialization are usually programming errors. See also the doc on error handling.

It's a bit unclear how we should improve on this.

[robshaffbbc]

I think the main issue I had with this is that the user of the form has no idea what the problem is because the error message is just the standard form failed to load message. As for improvements I can think of a few options.

1. Pre-validation of the code used in the settings tab but this could create difficulties if you are using fields from the form as you never know the full range of data the code will see in the form.
2. There could be a more meaningful error message to indicate why the user can not open the form for editing (however I am not aware of any precedent set for this)
3. Just ignore the field if the code in it is not working. (and the user potentially wont know the field is broken if it defaults to visible)

So all of these have weaknesses but might be better than a general "form failed to load" page.

[ebruchez]

I guess it depends which user you are talking about ;)

If it's the end user of the form, then that user should see a nice error page, maybe with a code to help with support. But the end user probably doesn't care what the exact XPath error might have caused the issue.

If the user is the programmer, then sure, the error message should be the best possible.

BTW, are you using the dev run mode? Because that mode is supposed to show a detailed error message in the browser.

[robshaffbbc]

OK that is a fair distinction to make. We currently do not customise the default error page for our end user but we could make that nicer. On the dev side we cannot use dev mode due to https://github.com/orbeon/orbeon-forms/issues/1492 so we will have a solution to this on the next upgrade.

[robshaffbbc]

Closed this on the assumption that the error message in dev mode clarifies the reason for the form error.

[ebruchez]

Thanks, you'll let us know if you have more ideas as to how to improve this.