Does ANT apply prefixValues if there is no property of the desired name ? Or is this a bug ? (SSCCE provided)

I have this weird behavior with ant and properties and I'd like to know what do you think. I don't get the logic. This behavior could be usefull but I would like to know if I can rely on it or if this is a bug.

It looks like ant is applying the prefix when expanding the right hand side of properties if there is no property of the desired name. Here is the SSCCE:

build.properties:

a=A
formula=${a}

build.xml:

<project default="test">
    <target name="test">
        <property name="test.a" value="[test.a has been used instead of a, why? prefixValues is false]" />
        <property file="build.properties" prefix="test" prefixValues="false" />
        <echo>${test.formula}</echo>
    </target>
</project>

output:

test:
    [echo] [test.a has been used instead of a, why? prefixValues is false]
BUILD SUCCESSFUL
Total time: 364 milliseconds

As you can see, test.formula should use "a" and not "test.a" but "a" is never defined. Is it the reason?

Solution

I ran some more test and could get a lot of different results.

After checking the sources, I think that there is a bug when looking for properties while adding them through a file. By modifying some ant source code, I could get it to work.

In the end, I decided to fill a bug report (https://issues.apache.org/bugzilla/show_bug.cgi?id=54769) with a proposed patch.

Thank you all.