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

You can just use the overwrite attribute also.

<property name="ernex.core.build" value="Latest" overwrite="false" />

We use this also to specify a default setting mostly for properties that will be set from the command line. debug mode for example.

<property name="debug" value="false" overwrite="false" />

BOb



From: Christopher Brandt [mailto:[email protected]]
Sent: Tuesday, April 13, 2010 11:55 AM
To: NAnt Users
Cc: Durand Van Arnem; Bob Archer
Subject: Re: [NAnt-users] Using "if" to test for existence of properties

Same strategy here; ensure the property exists and then use the if attribute to test its value. One place where you can use the if / unless attributes to test existence is in setting the property itself, so giving it a default value. We use the following to ensure that required properties are at least set to a default value:

<property name="ernex.core.build" value="Latest" unless="${property::exists('ernex.core.build')}" />

Hope that helps
---
Chris.

Continuous improvement is better than delayed perfection. - Mark Twain

On Tue, Apr 13, 2010 at 7:51 AM, Bob Archer <[email protected]<mailto:[email protected]>> wrote:
I think I have run into this before. I think the easiest fix is to make sure the property always exists. Then you can check to see if it is not empty.

BOb


From: Durand Van Arnem [mailto:[email protected]<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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