Forum OpenACS Q&A: if/else tags in adp

Reuven,

I didn't know about this. Thanks for catching and letting us know.

When troubleshooting things like this, I usually copy the packages/acs-templating/www/doc/demo/compile.tcl script to the directory where my templates are, and then request compile?file=foo.adp. This gives you the code being generated by from the ADP template, and makes it a lot easier to troubleshoot what's going on.

In this example, I have this template:

<% set foo 1 %>

<if @foo@ true>Something</if>

Here's a bit of html.

<else>Something else.</else>

Which is translated into:

set __adp_output ""

set foo 1

if {[template::util::is_true "${foo}"]} {

append __adp_output "Something"

}

append __adp_output "

Here's a bit of html.

" else {

append __adp_output "Something else."
}

set __adp_output

So you can see what's happening: The <else> tag just appends " else {...}" to whatever line happens to be the latest one written so far. Since that in this case is the "append __adp_output" command, the else block is simply appended.

Here's the implementation of the tag:

template_tag else { chunk params } {

  template::adp_append_code "else {" -nobreak

  template::adp_compile_chunk $chunk

  template::adp_append_code "}"

}

So what would it take to fix? We'd have to save either the expression or the result of evaluating the expression from the <if> tag onto some sort of stack, and then pop the stack in the else tag.

Not impossible. And the current implementation of the <else> tag is, to say the least, not very robust.

Of course, it's easy to change the ADP file to not do this. You can just have two <if> chunks with inverted arguments.

Comments, others?

/Lars

Tom,

I agree that there isn't any good reason to have text between the </if> and <else> tags.  But the graphic designer (who is the client) didn't know this, and reported that weird things were happening to her pages.

So I'm not really asking for ADP to allow random stuff between </if> and <else>.  Rather, I'm asking that (a) this restriction be made explicit in the documentation, and (b) the error message make the error more obvious, so that designers and programmers alike aren't confused and surprised when funny things happen.

Let's just agree it's a bug :)

Lars, did you dig into this enough to figure out how to fix it?  I think the fix is simple: whitespace followed by an optional tag (to account for ifs at the end of a script) are the only things that are legal after the close-if tag.

Here is a short shell script that can help identify problems with .adp's. (Improperly closed <if> & <else> tags, improperly nested tags, etc.) In fact, it's more rigorous about well-formed .adp code than the ACS code. I wrote it to help our graphic designer find a missing </if> in an .adp that had grown to several thousand lines long.

Usage: save as adp-validate, stick it somewhere in your $PATH and then run: adp-validate *.adp from a shell.

#!/bin/sh
# -*- tcl -*- 
exec tclsh "$0" "$@"

package require Tcl 8.3
 
package require nstcl-templating
package require fileutil
 
foreach file $argv {
    if [catch {
        ::nstcl::template::adp::adp_to_pseudo_code [fileutil::cat $file]
    } problem] {
        puts stderr "$file ==> $problem"
    } else {
        puts "$file ==> OK"
    }
}