Retrieve property value from include'd / import'ed project - ant

Question

I am trying to use ant's include or import tasks to use a common build file. I am stuck at retrieving properties from included file.
These are my non-working samples, trying to retrieve "child-property"
Using ant import
parent file
<?xml version="1.0" encoding="UTF-8"?>
<project name="parent" basedir=".">
<import file="child.xml" />
<target name="parent-target">
<antcall target="child-target" />
<echo message="(From Parent) ${child-property}" />
</target>
</project>
child file
<?xml version="1.0" encoding="UTF-8"?>
<project name="child" basedir=".">
<target name="child-target">
<property name="child-property" value="i am child value" />
<echo message="(From Child) ${child-property}" />
</target>
</project>
output
parent-target:
child-target:
[echo] (From Child) i am child value
[echo] (From Parent) ${child-property}
Using ant include
parent file
<project name="parent" basedir=".">
<include file="child.xml" />
<target name="parent-target">
<antcall target="child.child-target" />
<echo message="(From Parent) ${child-property}" />
<echo message="(From Parent2) ${child.child-property}" />
</target>
</project>
child file
same as above
output
parent-target:
child.child-target:
[echo] (From Child) i am child value
[echo] (From Parent) ${child-property}
[echo] (From Parent2) ${child.child-property}
How can I access "child-property" from parent?

Answer 1

When you use the antcall task a new Ant cycle is started for the antcall'ed task - but that doesn't affect the context of the caller:
The called target(s) are run in a new
project; be aware that this means
properties, references, etc. set by
called targets will not persist back
to the calling project.
One way to make your simple example to work would be to change the first parent to:
<target name="parent-target" depends="child-target">
<echo message="(From Parent) ${child-property}" />
</target>
Then the child-target will be executed in the parent context before the parent-target.
But, you may find that there are side affects to running the child task in the context of the parent that you don't want.

Answer 2

It is a different approach but you may use macrodef.
parent.xml
<?xml version="1.0" encoding="UTF-8"?>
<project name="parent" basedir=".">
<import file="child.xml"/>
<target name="parent-target">
<child-macro myid="test"/>
<echo message="(From Parent) ${child-property}" />
</target>
child.xml
<?xml version="1.0" encoding="UTF-8"?>
<project name="child" basedir=".">
<macrodef name="child-macro">
<attribute name="myid" default=""/>
<sequential>
<property name="child-property" value="i am child value" />
<echo message="(From Child) ${child-property}" />
<echo message="Received params: myId=#{myid}"/>
</sequential>
</macrodef>
</project>
output
parent-target:
[echo] (From Child) i am child value
[echo] Received params: myId=test
[echo] (From Parent) i am child value

Answer 3

Ant-contrib's runtarget task has sufficiently solved my problem. It mignt not be suitable for others since it runs the target in parent's context. Guess there is no "one solution for all" for these kind of problems until Ant officially supports variables.
Parent
<project name="parent" basedir=".">
<!-- insert necessary antcontrib taskdef here-->
<include file="child.xml" />
<target name="parent-target">
<var name="x" value="x"/>
<runtarget target="child.child-target"/>
<echo message="From Parent: ${x}"/>
</target>
</project>
Child
<project name="child" basedir=".">
<property name="pre" value="childpre" />
<target name="child-target">
<var name="x" value="${x}y" />
</target>
</project>
Output
parent-target:
child.child-target:
[echo] From Parent: xy