Re: Using "if" to test for existence of properties

Hello,

Maybe I am missing something here, but, I tried this using the following:

<if test="${property::exists('MyProperty')}">
                                                <echo message="${MyProperty}" />
                                </if>

This executed without failure, but, I did not define "MyProperty" at all, so, I added this to the above, outside of the target that was running, i.e.:

<?xml version="1.0" encoding="utf-8" ?>
<project name="test" basedir="." default="build">

                                                <property name="MyProperty" value="" />

                                                <target name="build">
                                                                <if test="${property::exists('MyProperty')}">
                                                                                <echo message="${MyProperty}" />
                                                                </if>
                                                </target>
</project>

This also executed without failure, essentially echoing a "[echo]" with no text.

As I stated, I may be missing something here, but, this appears to work fine (in NAnt 0.86 ...). Please let me know if I have misunderstood your issue.

Thanks,
Mike

From: Durand Van Arnem [mailto:[email protected]]
Sent: Tuesday, April 13, 2010 10:33 AM
To: NAnt Users
Subject: [NAnt-users] Using "if" to test for existence of properties

Hello,

I could use some advice about how to handle this situation:

I have a property, MyProperty, that may or may not be set.  I want a task to execute if the property is set, e.g.
<echo messsage="Hello ${MyProperty}!" if="${property::exists('MyProperty')" />

If MyProperty is not set, this task fails because NAnt appears to evaluate the message portion regardless of the result of the IF evaluation.  I could rewrite like this:

<if test="${property::exists('MyProperty')}">
    <echo message="Hello ${MyProperty}!" />
</if>

However, I run into the same issue with filterchains:

<!-- FAILS if MyProperty is not set, because NAnt evaluates the tokens regardless of the IF result -->
<copy failonerror="true" verbose="true" todir="C:\Temp">
    <fileset refid="Deploy-FileSet" />
    <filterchain>
        <replacetokens begintoken="[" endtoken="]" ignorecase="true" if="${property::exists('MyProperty')}">
            <token key="ABC" value="${MyProperty}" />
        </replacetokens>
    </filterchain>
</copy>

I'd rather not enclose the whole definition of the copy in an IF, with a nearly identical "else" version for the case when MyProperty is not set.

How have you handled this situation?

Thanks,
Durand

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