8361587: AssertionError in File.listFiles() when path is empty and -esa is enabled

src/java.base/share/classes/java/io/File.java

@@ -264,7 +264,6 @@ private File(String pathname, int prefixLength) {
      */
     private File(String child, File parent) {
         assert parent.path != null;
-        assert (!parent.path.isEmpty());
         this.path = FS.resolve(parent.path, child);
         this.prefixLength = parent.prefixLength;
     }

src/java.base/unix/classes/java/io/UnixFileSystem.java

@@ -117,6 +117,7 @@ private static String trimSeparator(String s) {
     @Override
     public String resolve(String parent, String child) {
         if (child.isEmpty()) return parent;
+        if (parent.isEmpty()) return child;
         if (child.charAt(0) == '/') {
             if (parent.equals("/")) return child;
             return trimSeparator(parent + child);

test/jdk/java/io/File/EmptyPath.java

@@ -22,7 +22,7 @@
  */
 
 /* @test
- * @bug 4842706 8024695
+ * @bug 4842706 8024695 8361587
  * @summary Test some file operations with empty path
  * @run junit EmptyPath
  */
@@ -36,7 +36,9 @@
 import java.nio.file.Path;
 import java.util.Arrays;
 import java.util.HashSet;
+import java.util.List;
 import java.util.Set;
+import java.util.stream.Collectors;
 
 import org.junit.jupiter.api.BeforeAll;
 import org.junit.jupiter.api.Test;
@@ -105,13 +107,28 @@ public void exists() {
         assertTrue(f.exists());
     }
 
+    @Test
+    public void getAbsoluteFile() {
+        assertEquals(p.toAbsolutePath().toFile(), f.getAbsoluteFile());
+    }
+
     @Test
     public void getAbsolutePath() {
         System.out.println(p.toAbsolutePath().toString() + "\n" +
                            f.getAbsolutePath());
         assertEquals(p.toAbsolutePath().toString(), f.getAbsolutePath());
     }
 
+    @Test
+    public void getCanonicalFile() throws IOException {
+        assertEquals(p.toRealPath().toFile(), f.getCanonicalFile());
+    }
+
+    @Test
+    public void getCanonicalPath() throws IOException {
+        assertEquals(p.toRealPath().toString(), f.getCanonicalPath());
+    }
+
     private void checkSpace(long expected, long actual) {
         if (expected == 0) {
             assertEquals(0L, actual);
@@ -136,6 +153,11 @@ public void getParent() {
         assertNull(f.getParent());
     }
 
+    @Test
+    public void getParentFile() {
+        assertNull(f.getParentFile());
+    }
+
     @Test
     public void getPath() {
         assertEquals(p.toString(), f.getPath());
@@ -198,11 +220,58 @@ public void list() throws IOException {
         assertEquals(nioSet, ioSet);
     }
 
+    @Test
+    public void listFiles() throws IOException {
+        File child = new File(f.getAbsoluteFile(), "child");
+        assertTrue(child.createNewFile());
+        child.deleteOnExit();
+
+        File[] files = f.listFiles();
+        for (File file : files)
+            assertEquals(-1, f.toString().indexOf(File.separatorChar));
+
+        Set<String> ioSet = Arrays.stream(files)
+            .map(File::getName)
+            .collect(Collectors.toSet());
+
+        assertTrue(ioSet.contains(child.getName()));
+
+        Set<String> nioSet = Files.list(p)
+            .map(Path::getFileName)
+            .map(Path::toString)
+            .collect(Collectors.toSet());
+        assertEquals(nioSet, ioSet);
+    }
+
+    @Test
+    public void listRoots() {
+        Set<String> expected = Arrays.stream(f.getAbsoluteFile().listRoots())
+            .map(File::toString)
+            .collect(Collectors.toSet());
+        Set<String> actual = Arrays.stream(f.listRoots())
+            .map(File::toString)
+            .collect(Collectors.toSet());
+        assertEquals(expected, actual);
+    }
+
     @Test
     public void mkdir() {
         assertFalse(f.mkdir());
     }
 
+    @Test
+    public void mkdirs() {
+        File child = new File(f, "child");
+        assertFalse(child.mkdirs());
+    }
+
+    @Test
+    public void renameTo() throws IOException {
+        File tmp = File.createTempFile("foo", "bar", f.getAbsoluteFile());
+        assertTrue(tmp.exists());
+        assertFalse(f.renameTo(tmp));
+    }
+
     @Test
     public void setLastModified() {
         long t0 = f.lastModified();
@@ -271,6 +340,12 @@ public void toPath() {
         assertEquals(p, f.toPath());
     }
 
+    @Test
+    public String toString() {
+        assertEquals(EMPTY_STRING, f.toString());
+        return EMPTY_STRING;
+    }
+
     @Test
     public void toURI() {
         assertEquals(f.toPath().toUri(), f.toURI());