Forum OpenACS Development: template::list pagination in a xowiki page

I have built some UI pages using template::list in pages initialized by "::xowiki::Package initialize" rather than ad_page_contract.

I have found that when using pagination, links to pages show an issue: "::xowiki::Package initialize" transforms every specified, but empty variable passed to the query into a "{}".

If I say, for instance "my-page?page=&orderby=column,asc", ad_page_contract will set a variable $page as the empty string, while "::xowiki::Package initialize" will give me an empty brackets list. With this last behavior, the page will return an error, because $page is not a number.

I have found that if we change template::list::get_url, so it doesn't export empty variables at all using "-no_empty" flag, the problem goes away.

I have tested on my busy installation using lists all over the place and I haven't found regressions. If ok I can commit.

http://www.openacs.org/api-doc/proc-view?proc=template%3a%3alist%3a%3aget_url&source_p=1

All the best.

Together with the filter I click, list machinery exports also every other page variable, so the list doesn't forget all other filters, but just adds the one I have clicked. In this situation, if we export empty variables, xowiki initialization puts the extra brackets into play.

Another situation where this happens is when we come back to a template::list:: page initialized in xowiki from a url created by "ad_return_url". This proc exports every variable, including empty ones, so xowiki initialization will treat them as "{}".

Real example: I have a list where I filter my entries by title. This list is created by template::list into a "xowiki initialized" page. In the list I have "edit" action, and I create the url so that when I finish editing, I am taken back to the list I was looking before. This url is created by ad_return_url. Leaving empty the "title" textfield of my form makes so that when I come back, textfield contains a "{}", and my entries are not shown because they don't match this pattern.

The solution for me was replacing "ad_return_url" with "export_vars -base [ad_conn url] -entire_form -no_empty" that basically is the same thing, but without exporting empty vars.

Xowiki's approach is probably more correct, because we could have mandatory variables that are just good as empty strings, and removing them could cause failures by the page contract. It would be just great if they could stay the empty string and don't turn "{}", otherwise template:: machinery and xowiki's become harder to mix.