[MCLEAN-124] Leverage Files.delete(Path) API to provide more accurate reason in case of failure

src/main/java/org/apache/maven/plugins/clean/Cleaner.java

@@ -273,7 +273,8 @@ private boolean isSymbolicLink(Path path) throws IOException {
      * @throws IOException If a file/directory could not be deleted and <code>failOnError</code> is <code>true</code>.
      */
     private int delete(File file, boolean failOnError, boolean retryOnError) throws IOException {
-        if (!file.delete()) {
+        IOException error = delete(file);
+        if (error != null) {
             boolean deleted = false;
 
             if (retryOnError) {
@@ -289,18 +290,18 @@ private int delete(File file, boolean failOnError, boolean retryOnError) throws
                     } catch (InterruptedException e) {
                         // ignore
                     }
-                    deleted = file.delete() || !file.exists();
+                    deleted = delete(file) == null || !file.exists();
                 }
             } else {
                 deleted = !file.exists();
             }
 
             if (!deleted) {
                 if (failOnError) {
-                    throw new IOException("Failed to delete " + file);
+                    throw new IOException("Failed to delete " + file, error);
                 } else {
                     if (log.isWarnEnabled()) {
-                        log.warn("Failed to delete " + file);
+                        log.warn("Failed to delete " + file, error);
                     }
                     return 1;
                 }
@@ -310,6 +311,15 @@ private int delete(File file, boolean failOnError, boolean retryOnError) throws
         return 0;
     }
 
+    private static IOException delete(File file) {
+        try {
+            Files.delete(file.toPath());
+        } catch (IOException e) {
+            return e;
+        }
+        return null;
+    }
+
     private static class Result {
 
         private int failures;

src/test/java/org/apache/maven/plugins/clean/CleanerTest.java

@@ -0,0 +1,183 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.apache.maven.plugins.clean;
+
+import java.io.IOException;
+import java.nio.file.AccessDeniedException;
+import java.nio.file.DirectoryNotEmptyException;
+import java.nio.file.Path;
+import java.nio.file.attribute.PosixFilePermission;
+import java.nio.file.attribute.PosixFilePermissions;
+import java.util.Iterator;
+import java.util.LinkedHashMap;
+import java.util.Map;
+import java.util.Map.Entry;
+import java.util.Set;
+
+import org.apache.maven.plugin.logging.Log;
+import org.apache.maven.plugin.testing.SilentLog;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+
+import static java.nio.file.Files.createDirectory;
+import static java.nio.file.Files.createFile;
+import static java.nio.file.Files.exists;
+import static java.nio.file.Files.getPosixFilePermissions;
+import static java.nio.file.Files.setPosixFilePermissions;
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertInstanceOf;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+class CleanerTest {
+
+    private boolean warnEnabled;
+
+    /**
+     * Use a {@code LinkedHashMap} to preserve the order of the logged warnings.
+     */
+    private final Map<CharSequence, Throwable> warnings = new LinkedHashMap<>();
+
+    /**
+     * Ideally we should use a mocking framework such as Mockito for this, but alas, this project has no such dependency.
+     */
+    private final Log log = new SilentLog() {
+
+        @Override
+        public boolean isWarnEnabled() {
+            return warnEnabled;
+        }
+
+        @Override
+        public void warn(CharSequence content, Throwable error) {
+            warnings.put(content, error);
+        }
+    };
+
+    @Test
+    void deleteSucceedsDeeply(@TempDir Path tempDir) throws Exception {
+        final Path basedir = createDirectory(tempDir.resolve("target"));
+        final Path file = createFile(basedir.resolve("file"));
+        final Cleaner cleaner = new Cleaner(null, log, false, null, null);
+        cleaner.delete(basedir.toFile(), null, false, true, false);
+        assertFalse(exists(basedir));
+        assertFalse(exists(file));
+    }
+
+    @Test
+    void deleteFailsWithoutRetryWhenNoPermission(@TempDir Path tempDir) throws Exception {
+        warnEnabled = true;
+        final Path basedir = createDirectory(tempDir.resolve("target"));
+        createFile(basedir.resolve("file"));
+        final Set<PosixFilePermission> initialPermissions = getPosixFilePermissions(basedir);
+        final String rwxrwxr_x = PosixFilePermissions.toString(initialPermissions);
+        // Prevent directory listing, which will result in a DirectoryNotEmptyException.
+        final String rw_rw_r__ = rwxrwxr_x.replace('x', '-');
+        final Set<PosixFilePermission> permissions = PosixFilePermissions.fromString(rw_rw_r__);
+        setPosixFilePermissions(basedir, permissions);
+        try {
+            final Cleaner cleaner = new Cleaner(null, log, false, null, null);
+            final IOException exception =
+                    assertThrows(IOException.class, () -> cleaner.delete(basedir.toFile(), null, false, true, false));
+            assertTrue(warnings.isEmpty());
+            assertEquals("Failed to delete " + basedir, exception.getMessage());
+            final DirectoryNotEmptyException cause =
+                    assertInstanceOf(DirectoryNotEmptyException.class, exception.getCause());
+            assertEquals(basedir.toString(), cause.getMessage());
+        } finally {
+            // Allow the tempDir to be cleared by the @TempDir extension.
+            setPosixFilePermissions(basedir, initialPermissions);
+        }
+    }
+
+    @Test
+    void deleteFailsAfterRetryWhenNoPermission(@TempDir Path tempDir) throws Exception {
+        final Path basedir = createDirectory(tempDir.resolve("target"));
+        createFile(basedir.resolve("file"));
+        final Set<PosixFilePermission> initialPermissions = getPosixFilePermissions(basedir);
+        final String rwxrwxr_x = PosixFilePermissions.toString(initialPermissions);
+        // Prevent directory listing, which will result in a DirectoryNotEmptyException.
+        final String rw_rw_r__ = rwxrwxr_x.replace('x', '-');
+        final Set<PosixFilePermission> permissions = PosixFilePermissions.fromString(rw_rw_r__);
+        setPosixFilePermissions(basedir, permissions);
+        try {
+            final Cleaner cleaner = new Cleaner(null, log, false, null, null);
+            final IOException exception =
+                    assertThrows(IOException.class, () -> cleaner.delete(basedir.toFile(), null, false, true, true));
+            assertEquals("Failed to delete " + basedir, exception.getMessage());
+            final DirectoryNotEmptyException cause =
+                    assertInstanceOf(DirectoryNotEmptyException.class, exception.getCause());
+            assertEquals(basedir.toString(), cause.getMessage());
+        } finally {
+            // Allow the tempDir to be cleared by the @TempDir extension.
+            setPosixFilePermissions(basedir, initialPermissions);
+        }
+    }
+
+    @Test
+    void deleteLogsWarningWithoutRetryWhenNoPermission(@TempDir Path tempDir) throws Exception {
+        warnEnabled = true;
+        final Path basedir = createDirectory(tempDir.resolve("target"));
+        final Path file = createFile(basedir.resolve("file"));
+        final Set<PosixFilePermission> initialPermissions = getPosixFilePermissions(basedir);
+        final String rwxrwxr_x = PosixFilePermissions.toString(initialPermissions);
+        final String r_xr_xr_x = rwxrwxr_x.replace('w', '-');
+        final Set<PosixFilePermission> permissions = PosixFilePermissions.fromString(r_xr_xr_x);
+        setPosixFilePermissions(basedir, permissions);
+        try {
+            final Cleaner cleaner = new Cleaner(null, log, false, null, null);
+            assertDoesNotThrow(() -> cleaner.delete(basedir.toFile(), null, false, false, false));
+            assertEquals(2, warnings.size());
+            final Iterator<Entry<CharSequence, Throwable>> it =
+                    warnings.entrySet().iterator();
+            final Entry<CharSequence, Throwable> warning1 = it.next();
+            assertEquals("Failed to delete " + file, warning1.getKey());
+            final AccessDeniedException cause1 = assertInstanceOf(AccessDeniedException.class, warning1.getValue());
+            assertEquals(file.toString(), cause1.getMessage());
+            final Entry<CharSequence, Throwable> warning2 = it.next();
+            assertEquals("Failed to delete " + basedir, warning2.getKey());
+            final DirectoryNotEmptyException cause2 =
+                    assertInstanceOf(DirectoryNotEmptyException.class, warning2.getValue());
+            assertEquals(basedir.toString(), cause2.getMessage());
+        } finally {
+            setPosixFilePermissions(basedir, initialPermissions);
+        }
+    }
+
+    @Test
+    void deleteDoesNotLogAnythingWhenNoPermissionAndWarnDisabled(@TempDir Path tempDir) throws Exception {
+        warnEnabled = false;
+        final Path basedir = createDirectory(tempDir.resolve("target"));
+        createFile(basedir.resolve("file"));
+        final Set<PosixFilePermission> initialPermissions = getPosixFilePermissions(basedir);
+        final String rwxrwxr_x = PosixFilePermissions.toString(initialPermissions);
+        final String r_xr_xr_x = rwxrwxr_x.replace('w', '-');
+        final Set<PosixFilePermission> permissions = PosixFilePermissions.fromString(r_xr_xr_x);
+        setPosixFilePermissions(basedir, permissions);
+        try {
+            final Cleaner cleaner = new Cleaner(null, log, false, null, null);
+            assertDoesNotThrow(() -> cleaner.delete(basedir.toFile(), null, false, false, false));
+            assertTrue(warnings.isEmpty());
+        } finally {
+            setPosixFilePermissions(basedir, initialPermissions);
+        }
+    }
+}