def dir = file('data')

// end::workaround[]
def listFiles(File dir) {
    dir.listFiles({ file -> file.isFile() } as FileFilter).name.sort()
}

tasks.register('listFiles') {
    doLast {
        println listFiles(dir)
    }
}
// end::not-supported[]

// tag::workaround[]
class Files {
    static def listFiles(File dir) {
        dir.listFiles({ file -> file.isFile() } as FileFilter).name.sort()
    }
}

// tag::not-supported[]
val dir = file("data")

fun listFiles(dir: File): List<String> =
    dir.listFiles { file: File -> file.isFile }.map { it.name }.sorted()

tasks.register("listFiles") {
    doLast {
        println(listFiles(dir))
    }
}
// end::not-supported[]

// tag::workaround[]
object Files { // <1>
    fun listFiles(dir: File): List<String> =
        dir.listFiles { file: File -> file.isFile }.map { it.name }.sorted()
}

Execution failed for task ':listFiles'.

        then:
        !objectFile(orgFile)
        objectFile(movedFile)
    }

    def objectFile(TestFile testFile) {
        assert outputDir.listFiles().size() == 1
        assert outputDir.listFiles()[0].listFiles().size() == 1
        outputDir.listFiles()[0].listFiles()[0].text == testFile.absolutePath
    }

    def compile(TestFile... sourceToCompile) {
        List<TestFile> toCompile = Arrays.asList(sourceToCompile)

        this.additionalParameters = additionalParameters;
    }

    public boolean isListFiles() {
        return listFiles;
    }

    public void setListFiles(boolean listFiles) {
        this.listFiles = listFiles;
    }

    public String getLoggingLevel() {
        return loggingLevel;
    }

    public void setLoggingLevel(String loggingLevel) {

                "File(\"$directoryPath\").listFiles()"
            }

            @Override
            String getJavaExpression() {
                "new File(\"$directoryPath\").listFiles()"
            }

            @Override
            String getGroovyExpression() {
                "new File(\"$directoryPath\").listFiles()"
            }
        }
    }

 */
fun FileSystemOperations.removeOldVersionsFromDir(dir: Directory, shouldDelete: Spec<GradleVersion>, dirPrefix: String = "", dirSuffix: String = "") {
    if (dir.asFile.isDirectory) {
        for (cacheDir in dir.asFile.listFiles()) {
            val cacheDirName = cacheDir.name
            if (!cacheDirName.startsWith(dirPrefix) || !cacheDirName.endsWith(dirSuffix)) {
                continue
            }

        assertInstalled()
        return scriptFile().exec(args)
    }

    private TestFile scriptFile() {
        if (os.windows) {
            return installDir.listFiles().find { it.file && it.name.endsWith(".bat") }
        } else {
            return installDir.listFiles().find { it.file }
        }
    }

    NativeInstallationFixture assertInstalled() {
        installDir.assertIsDir()
        final script = scriptFile()

    }

    private List<File> listDirs(File baseDir) {
        return listFiles(baseDir, directoryFileFilter());
    }

    private List<File> listFiles(File baseDir) {
        return listFiles(baseDir, null);
    }

    private List<File> listFiles(File baseDir, @Nullable FileFilter filter) {
        File[] dirs = baseDir.listFiles(filter);
        return dirs == null ? Collections.<File>emptyList() : Arrays.asList(dirs);

    }

    public void setVerbose(boolean verbose) {
        this.verbose = verbose;
    }

    public boolean isListFiles() {
        return listFiles;
    }

    public void setListFiles(boolean listFiles) {
        this.listFiles = listFiles;
    }

    public String getEncoding() {
        return encoding;
    }

    public void setEncoding(String encoding) {
        this.encoding = encoding;