Checking a reference with ant

Is there any way to check in ant that a reference with specific refid is defined somewhere?

For example, I need to check that my.ref is defined before using it as follows.

<pathconvert property="my.prop" refid="my.ref">
...
</pathconvert>

I need to do it since in my project there are some build scripts which not under my control (actually, I am not allowed to examine their content sometimes).

These scripts are supposed to define this reference. Unfortunately, I can't count that this reference is defined due to some reason.

So, I need to check it and perform graceful error handling or some specific actions.

Is there any way to do it?

Update:

I found the correct way to do it myself. It can be done by using isreference elem开发者_如何学运维ent of the condition task.

For instance:

<condition property="my.ref.defined">
    <isreference refid="my.ref"/>
</condition>
<fail unless="my.ref.defined" message="Reference my.ref not defined."/>

You can set a property based on the value of a reference, then test that property. For example:

<property name="my.prop" value="${toString:my.ref}" />

To make sure it works with all types of references it's better to use ${ant.refid:reference}, see Ant Manual, though it works with ${toString:reference} in most cases.

With Ant Plugin Flaka it's a one-liner =

 <project name="demo" xmlns:fl="antlib:it.haefelinger.flaka">
  <fl:fail message="Houston we have a problem" test="not has.property['ant.refid:my.ref']"/>

Flaka has also control structures like when, unless, while, for, choose, switch ..

 <fl:when test="not has.property['ant.refid:my.ref']">
  ...
 </fl:when>

see Flaka Manual