code: protected Set<File> jrxmlFilesToCompile(SourceMapping mapping) throws MojoExecutionException {
  		if (!sourceDirectory.isDirectory()) {
  			String message = sourceDirectory.getName() + " is not a directory";
  			if (failOnMissingSourceDirectory) {
  				throw new IllegalArgumentException(message);
  			}
  			else {
  				log.warn(message + ", skip JasperReports reports compiling.");
  				return Collections.emptySet();
  			}
  		}
  
  		try {
  			SourceInclusionScanner scanner = createSourceInclusionScanner();
  			scanner.addSourceMapping(mapping);
  			return scanner.getIncludedSources(sourceDirectory, outputDirectory);
  		}
  		catch (InclusionScanException e) {
  			throw new MojoExecutionException("Error scanning source root: \'" + sourceDirectory + "\'.", e);
  		}
  	}
docs: Determines source files to be compiled.
  
  @param mapping The source files
  
  @return set of jxml files to compile
  
  @throws MojoExecutionException When there's trouble with the input