Fix extraction

Author: larsgrefer

sass-embedded-host/src/main/java/de/larsgrefer/sass/embedded/connection/DartSassPackageProvider.java

@@ -37,10 +37,12 @@ synchronized File extractPackage() throws IOException {
 
         Path targetPath = getTargetPath();
 
-        try {
-            IOUtils.extract(dist, targetPath);
-        } catch (IOException e) {
-            throw new IOException(String.format("Failed to extract %s into %s", dist, targetPath), e);
+        if (IOUtils.isEmpty(targetPath)) {
+            try {
+                IOUtils.extract(dist, targetPath);
+            } catch (IOException e) {
+                throw new IOException(String.format("Failed to extract %s into %s", dist, targetPath), e);
+            }
         }
 
         File execDir = targetPath.resolve("dart-sass").toFile();

sass-embedded-host/src/main/java/de/larsgrefer/sass/embedded/util/IOUtils.java

@@ -13,6 +13,7 @@
 import java.nio.file.Path;
 import java.nio.file.StandardCopyOption;
 import java.util.concurrent.TimeUnit;
+import java.util.stream.Stream;
 import java.util.zip.ZipEntry;
 import java.util.zip.ZipInputStream;
 
@@ -23,6 +24,20 @@
 @RequiresApi(10000)
 public class IOUtils {
 
+    public static boolean isEmpty(Path path) throws IOException {
+        if (Files.notExists(path)) {
+            return true;
+        }
+
+        if (Files.isDirectory(path)) {
+            try (Stream<Path> walk = Files.walk(path)) {
+                return walk.noneMatch(Files::isRegularFile);
+            }
+        }
+
+        return false;
+    }
+
     public static void extract(URL archiveUrl, Path destinationDir) throws IOException {
         String file = archiveUrl.getPath();
         if (file.endsWith(".zip")) {

sass-embedded-host/src/test/java/de/larsgrefer/sass/embedded/util/IOUtilsTest.java

@@ -0,0 +1,36 @@
+package de.larsgrefer.sass.embedded.util;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+
+import java.io.File;
+import java.io.IOException;
+import java.nio.file.Path;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.jupiter.api.Assertions.*;
+
+class IOUtilsTest {
+
+    @Test
+    void isEmpty(@TempDir Path tempDir) throws IOException {
+
+        assertThat(IOUtils.isEmpty(tempDir)).isTrue();
+
+        File subfolder1 = new File(tempDir.toFile(), "foo");
+        subfolder1.mkdir();
+
+        assertThat(IOUtils.isEmpty(tempDir)).isTrue();
+
+        File subfolder2 = new File(tempDir.toFile(), "bar");
+        subfolder2.mkdir();
+
+        assertThat(IOUtils.isEmpty(tempDir)).isTrue();
+
+        File file1 = new File(subfolder1, "dummy.txt");
+        file1.createNewFile();
+
+        assertThat(IOUtils.isEmpty(tempDir)).isFalse();
+
+    }
+}