build.gradle

buildscript {
    repositories {
        jcenter()
    }
    dependencies {
        classpath 'commons-io:commons-io:2.5'
    }
}

task embeddedInputs( type: EmbeddedInputs ) {
    sourceFile = file( 'src/one.src' )
    outputDir = new File( buildDir, 'compiled' )
}




class EmbeddedInputs extends DefaultTask {
    def m_cachedDeps = null

    def sourceFile

    def outputDir

    @InputFile
    File getSrcFile() {
        return project.file( sourceFile )
    }

    List<File> findDeps( File src ) {
        logger.info "Processing ${src} for dependencies"
        return src.readLines().findResults { line ->
            def result = ( line =~ /# dep:(.*)/ )
            if( result.matches() ) {
                return new File( src.parent, result[0][1] )
            }
            return null
        }
    }
        
    @InputFiles
    List<File> getDependencies() {
        /*
         * Since calculating this might be expensive, grab a cached result if possible (Gradle will call this
         * method more than once).
         * Duplicate dependency detection not present.
         */
        if( !m_cachedDeps ) {
            m_cachedDeps = []
            def toProcess = [srcFile]
            while( !toProcess.empty ) {
                def current = toProcess.pop()
                def deps = findDeps( current )
                toProcess.addAll( deps )
                m_cachedDeps.addAll( deps )
            }
        }
        return m_cachedDeps
    }

    @OutputFile
    File getOutFile() {
        return new File( project.file( outputDir ), "${org.apache.commons.io.FilenameUtils.getBaseName( srcFile.name )}.out" )
    }

    @TaskAction
    void compile() {
        logger.lifecycle "Compiling ${inputs.files as List} into ${outFile}"

        outFile.parentFile.mkdirs()

        outFile.withWriter() { writer ->
            inputs.files.each {
                logger.info "Processing ${it}"

                it.readLines().findResults { line ->
                    if( !line.startsWith( '#' ) ) {
                        writer.println line
                    }
                }
            }
        }
    }
}