Stop ant script without failing build - ant

Question

In my ant script I want to exit (stop executing build) without failing when a condition is met. I have tried to use:
<if>
<equals arg1="${variable1}" arg2="${variable2}" />
<then>
<fail status="0" message="No change, exit" />
</then>
</if>
Ant script is stopped on condition but build is failed. I want to the build to be stopped but with no errors. I'm using "Invoke Ant" step in Jenkins.
Thanks.

Answer 1

I would suggest to refactor your ant script by reconsidering your approach. If you approach your problem with "execution of a build when a certain condition is met" instead of "failing the build if another condition is met" it is easier to implement:
<!-- add on top of your build file -->
<if>
<equals arg1="${variable1}" arg2="${variable2}" />
<then>
<property name="runBuild" value="true"/>
</then>
<else>
<property name="runBuild" value="false"/>
</else>
</if>
<!-- add to the target that shall be executed conditionally -->
<target name="myTarget" if="${runBuild}">
...
<!-- exit message as separate target -->
<target name="exitTarget" unless="${runBuild}">
<echo message="No Change, exit" />
</target>

Answer 2

Use builtin (since JDK 6) javascript engine,
no additional libraries (antcontrib .. etc.) needed !
1. Java System.exit()
<script language="javascript">
self.log("Ending intentionally \n...\n..\n.");
java.lang.System.exit(0);
</script>
you may get a BUILD FAILED when running in Eclipse :
BUILD FAILED
javax.script.ScriptException: sun.org.mozilla.javascript.internal.WrappedException:
Wrapped org.eclipse.ant.internal.launching.remote.AntSecurityException
=> then use Ant api instead
2. Ant api
<script language="javascript">
self.log("Ending intentionally \n...\n..\n.");
project.fireBuildFinished(null);
</script>
Output Eclipse, no BUILD SUCCESSFUL is printed :
[script] Ending intentionally
[script] ...
[script] ..
[script] .
Total time: 410 milliseconds
Output Console, BUILD SUCCESSFUL is printed 2 times :
[script] Ending intentionally
[script] ...
[script] ..
[script] .
BUILD SUCCESSFUL
Total time: 0 seconds
BUILD SUCCESSFUL
Total time: 0 seconds
Wrap in a macrodef for reuse, f.e. :
<macrodef name="stopbuild">
<attribute name="condition"/>
<attribute name="paramtype" default="math"/>
<attribute name="param1"/>
<attribute name="param2"/>
<attribute name="when" default="true"/>
<sequential>
<script language="javascript">
falsecondition = false;
switch ("#{condition}")
{
case "lt" :
b = "#{paramtype}" == "math" ? parseInt("#{param1}") < parseInt("#{param2}") : "#{param1}" < "#{param2}";
break;
case "gt" :
b = "#{paramtype}" == "math" ? parseInt("#{param1}") > parseInt("#{param2}") : "#{param1}" > "#{param2}";
break;
case "eq" :
b = "#{paramtype}" == "math" ? parseInt("#{param1}") == parseInt("#{param2}") : "#{param1}" == "#{param2}";
break;
default:
self.log("Wrong condition : #{condition}, supported: lt, gt, eq");
falsecondition = true;
}
if(!falsecondition && b == java.lang.Boolean.valueOf("#{when}")) {
self.log("Stopping Build because #{param1} #{condition} #{param2} is #{when} !!");
java.lang.System.exit(0);
// alternatively use
//project.fireBuildFinished(null);
}
</script>
</sequential>
</macrodef>
Examples
<!-- compare int, default paramtype=math and when=true -->
<stopbuild param1="10" param2="11" condition="lt"/>
output :
[script] Stopping Build because 10 lt 11 is true !!
<!-- compare strings, default when=true -->
<stopbuild param1="abc" param2="abcd" paramtype="foo" condition="lt"/>
output :
[script] Stopping Build because abc lt abcd is true !!

Answer 3

Internally <fail> throws a BuildException to fail the build process, so, as long as you are using this task, you will get the ant build exit with errors.
Personally I don't know if there is any other task to "normally" exit the build, but writing one by yourself is not hard at all.
Writing a task which executes the following code should work...
public void execute() {
// do something as you like
System.exit(0);
}