Form with only a submit button no longer allowed.

[David Manns]

I have long used a form with just a 'Checkout' button in conjunction with a grid that displays the current state of a registration (multiple guests):

form2 = Form(fields, formstyle=FormStyleBulma, submit_value='Checkout')

This is no longer allowed, but I think it's a legitimate use case.

[Massimo DiPierro]

Not sure I understand this use case. Nothing should have changed. At least not intentionally. Can you provide a minimal example so I can reproduce?

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[David Manns]

I can certainly create a _minimal example, but to illustrate my use case I attach a screen shot, and I propose a small change to form.py below.

Creating an event registration in my app involves creating individual records for a member(host) and, possibly, their guest(s). Sometimes there are selections (e.g., meal choices, ticket options) to be made per guest. So I use a grid to build the overall registration.

I use a separate form to create a checkout button to confirm the registration and make payment. Sometimes this form contains an input field (e.g. a "how did you hear of this event" multichoice survey), but more often the form is simply a way of creating a nice consistent checkout button.

The commit https://github.com/web2py/py4web/commit/025c34c85eda16afb846725bcfb2f087210c039a made major changes to form.py and in particular at line 1036 raises an error if there are no fields in a form.

Removing that test/raise and adding "not all_tablenames or " to the last line of the following selection seems to work, one can once again have a form with just a button:

if isinstance(table, list):

# using _table to check if Field.bind was called

# and the field is bound to a table, since unlike `tablename`, `_table` is

# only set in Field.bind()

all_tablenames = list(

set(

str(getattr(field, "_table", None) or "no_table") for field in table

)

)

# only disable dbio if the fields are from multiple tables

# this allows making forms for a subset of fields easily:

# Form([db.tbl.field1, db.tbl.field2])

if not all_tablenames or len(all_tablenames) > 1 or all_tablenames[0] in "no_table":

[Massimo DiPierro]

Understood. Implemented as you suggested

[David Manns]

The fix works once the test and raise error are removed at form.py line 1036/7:

if isinstance(table, list):

fields_list = table

if len(fields_list) == 0:

raise ValueError("Cannot build form with empty list of fields")

[Massimo DiPierro]

fixed