public abstract ConfigurableFileCollection getSourceFiles();

    public void sources(FileCollection sourceFiles) {
        getSourceFiles().from(sourceFiles);
    }

    // ...
// end::custom-task-class[]

// tag::task-arg-method[]
    // ...
    public void sources(TaskProvider<?> inputTask) {
        getSourceFiles().from(inputTask);
    }
    // ...
// end::task-arg-method[]

    public abstract ConfigurableFileCollection getSourceFiles();

    public void sources(FileCollection sourceFiles) {
        getSourceFiles().from(sourceFiles);
    }

    // ...
// end::custom-task-class[]

// tag::task-arg-method[]
    // ...
    public void sources(TaskProvider<?> inputTask) {
        getSourceFiles().from(getProject().getLayout().files(inputTask));
    }
    // ...

        return headerFiles;
    }

    @Override
    public List<SourceFile> getSourceFiles() {
        ArrayList<SourceFile> sourceFiles = new ArrayList<SourceFile>();
        sourceFiles.addAll(getExecutable().getSourceFiles());
        sourceFiles.addAll(getLibrary().getSourceFiles());
        return sourceFiles;
    }

public abstract class ProcessTemplates extends DefaultTask {

    @Input
    public abstract Property<TemplateEngineType> getTemplateEngine();

    @InputFiles
    public abstract ConfigurableFileCollection getSourceFiles();

    @Nested
    public abstract TemplateData getTemplateData();

    @OutputDirectory
    public abstract DirectoryProperty getOutputDir();

    @Inject

public abstract class ProcessTemplates extends DefaultTask {

    @Input
    public abstract Property<TemplateEngineType> getTemplateEngine();

    @InputFiles
    public abstract ConfigurableFileCollection getSourceFiles();

    @Nested
    public abstract TemplateData getTemplateData();

    @OutputDirectory
    public abstract DirectoryProperty getOutputDir();

    @Inject

        // this mimics the behavior of the Ant javac task (and therefore AntJavaCompiler),
        // which silently excludes files not ending in .java
        Iterable<File> javaOnly = Iterables.filter(spec.getSourceFiles(), NormalizingJavaCompiler::hasJavaExtension);
        spec.setSourceFiles(ImmutableSet.copyOf(javaOnly));
    }

    private static boolean hasJavaExtension(@Nullable File input) {

    }

    @Internal
    public ConfigurableFileCollection getSourceFiles() {
        return sourceFiles;
    }

    @Input
    public Set<String> getSourceFilePaths() {
        return collect(getSourceFiles().getFiles(), File::getAbsolutePath);
    }

    @Internal
    public Set<File> getResourceFiles() {

    }

    @Override
    public boolean getHasSourceFiles() {
        throw failWithUnsupportedMethod("getHasSourceFiles()");
    }

    @Override
    public FileCollection getSourceFiles() {
        throw failWithUnsupportedMethod("getSourceFiles()");
    }

    List<TestFile> sourceFiles

    def setup() {
        _ * spec.objectFileDir >> outputDir
        _ * delegateCompiler.execute(_) >> { NativeCompileSpec spec ->
            List<File> sourceFiles = spec.getSourceFiles()
            sourceFiles.each{ inputFile ->
                createObjDummy(inputFile)
            }
            _ * workResult.getDidWork() >> !sourceFiles.isEmpty();
            return workResult
        }
    }

        logCompilerArguments(spec);
        return delegateAndHandleErrors(spec);
    }

    private void resolveSourceFiles(JavaCompileSpec spec) {
        spec.setSourceFiles(ImmutableSet.copyOf(spec.getSourceFiles()));
    }

    private void resolveClasspath(ScalaJavaJointCompileSpec spec) {
        List<File> classPath = Lists.newArrayList(spec.getCompileClasspath());
        classPath.add(spec.getDestinationDir());