Ivy optional configuration mapping (source, javadoc) - ivy

Question

Is it somehow possible to specify a optional defaultconfmapping for ivy?
What im looking for is to specify in the defaultconfmapping to get all source jars, but some lib dont have source jars available, and those would be fine to skip.
something like:
<dependencies defaultconf="default" defaultconfmapping="default->default,sources(?onlyifavailable)" >
is this somehow possible in ivy?
Else is there a way to only specify to NOT get a conf target?
ie:
<dependency org="org.lib" name="example" rev="default->!sources" />
The main thing i'm looking for is a way to define all (most) configuration mappings in the defaultconfmapping and not duplicate these mappings on individual items.
This means i'm looking for either an option to 'get but ignore if not there' or 'only adjust this part of the mapping without having to duplicate the parts that are still the same'
(one of the reasons is the large amount of dependecies we have)

Answer 1

If you have an empty fallback, it essentially makes the configuration optional:
<dependencies defaultconf="default" defaultconfmapping="default->default,sources()" >

Answer 2

Default configuration mappings are defined on the optional configuration declaration within your ivy file:
For example
<configurations defaultconfmapping="compile->default;sources;javadoc">
..
..
This creates 3 configuration mappings (which I think is what you're looking for):
compile->default
sources->sources
javadoc->javadoc
Personally I prefer to default an explicit configuration mapping on each dependency, but that's more pendantic.
Example
The following example generates an ivy report for each configuration and saves the source and javadoc jars in specific directories:
├── build.xml
├── ivy.xml
└── target
├── ivy-reports
│   ├── com.myspotontheweb-demo-compile.html
│   ├── com.myspotontheweb-demo-javadoc.html
│   ├── com.myspotontheweb-demo-runtime.html
│   ├── com.myspotontheweb-demo-sources.html
│   ├── com.myspotontheweb-demo-test.html
│   └── ivy-report.css
├── javadoc
│   ├── junit-4.11-javadoc.jar
│   ├── slf4j-api-1.7.5-javadoc.jar
│   └── slf4j-log4j12-1.7.5-javadoc.jar
└── sources
├── junit-4.11-sources.jar
├── slf4j-api-1.7.5-sources.jar
└── slf4j-log4j12-1.7.5-sources.jar
build.xml
<project name="demo" default="resolve" xmlns:ivy="antlib:org.apache.ivy.ant">
<!--
================
Build properties
================
-->
<property name="build.dir" location="target"/>
<target name="resolve" description="Use ivy to resolve classpaths">
<ivy:resolve/>
<ivy:report todir='${build.dir}/ivy-reports' graph='false' xml='false'/>
<ivy:cachepath pathid="compile.path" conf="compile"/>
<ivy:cachepath pathid="test.path" conf="test"/>
<ivy:retrieve pattern="${build.dir}/[conf]/[artifact]-[revision](-[classifier]).[ext]" conf="sources,javadoc"/>
</target>
</project>
ivy.xml
<ivy-module version="2.0">
<info organisation="com.myspotontheweb" module="demo"/>
<configurations defaultconfmapping="compile->default;sources;javadoc">
<conf name="compile" description="Required to compile application"/>
<conf name="sources" description="Source jars"/>
<conf name="javadoc" description="Javadoc jars"/>
<conf name="runtime" description="Additional run-time dependencies" extends="compile"/>
<conf name="test" description="Required for test only" extends="runtime"/>
</configurations>
<dependencies>
<!-- compile dependencies -->
<dependency org="org.slf4j" name="slf4j-api" rev="1.7.5"/>
<!-- runtime dependencies -->
<dependency org="org.slf4j" name="slf4j-log4j12" rev="1.7.5" conf="runtime->default;sources;javadoc"/>
<!-- test dependencies -->
<dependency org="junit" name="junit" rev="4.11" conf="test->default;sources;javadoc"/>
</dependencies>
</ivy-module>