Fix ScipWriter temp file creation on file systems without POSIX permissions

scip-aggregator/src/main/java/org/scip_code/scip_java/aggregator/ScipWriter.java

@@ -2,9 +2,11 @@
 
 import java.io.BufferedOutputStream;
 import java.io.IOException;
+import java.nio.file.FileSystems;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.nio.file.StandardCopyOption;
+import java.nio.file.attribute.FileAttribute;
 import java.nio.file.attribute.PosixFilePermissions;
 import org.scip_code.scip.Index;
 
@@ -16,15 +18,25 @@ public class ScipWriter implements AutoCloseable {
   private final ScipAggregatorOptions options;
 
   public ScipWriter(ScipAggregatorOptions options) throws IOException {
-    this.tmp =
-        Files.createTempFile(
-            "scip-aggregator",
-            "index.scip",
-            PosixFilePermissions.asFileAttribute(PosixFilePermissions.fromString("rw-r--r--")));
+    this.tmp = createTempFile();
     this.output = new ScipOutputStream(new BufferedOutputStream(Files.newOutputStream(tmp)));
     this.options = options;
   }
 
+  /**
+   * Creates the temporary output file with {@code rw-r--r--} permissions where the file system
+   * supports POSIX permissions. Other file systems (for example NTFS on Windows) reject the POSIX
+   * attribute, so the file is created with the default permissions there.
+   */
+  private static Path createTempFile() throws IOException {
+    if (FileSystems.getDefault().supportedFileAttributeViews().contains("posix")) {
+      FileAttribute<?> permissions =
+          PosixFilePermissions.asFileAttribute(PosixFilePermissions.fromString("rw-r--r--"));
+      return Files.createTempFile("scip-aggregator", "index.scip", permissions);
+    }
+    return Files.createTempFile("scip-aggregator", "index.scip");
+  }
+
   public void emitTyped(Index index) {
     this.output.write(index.toByteArray());
   }

scip-aggregator/src/test/java/org/scip_code/scip_java/aggregator/ScipWriterTest.java

@@ -0,0 +1,38 @@
+package org.scip_code.scip_java.aggregator;
+
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.List;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+import org.scip_code.scip.ToolInfo;
+
+/**
+ * Regression test for creating the temporary output file on file systems without POSIX permission
+ * support, such as NTFS on Windows.
+ */
+class ScipWriterTest {
+
+  @Test
+  void writesOutputFile(@TempDir Path dir) throws Exception {
+    Path output = dir.resolve("index.scip");
+    ScipAggregatorOptions options =
+        new ScipAggregatorOptions(
+            List.of(),
+            output,
+            dir,
+            new ScipAggregatorReporter() {},
+            ToolInfo.getDefaultInstance(),
+            false,
+            List.of(),
+            false,
+            true,
+            false);
+    try (ScipWriter writer = new ScipWriter(options)) {
+      writer.build();
+    }
+    assertTrue(Files.exists(output));
+  }
+}