feat: FileSystemProvider::readAttributes faked posix support (#1067)

google-cloud-nio/src/main/java/com/google/cloud/storage/contrib/nio/CloudStorageFileSystem.java

@@ -64,9 +64,11 @@ public final class CloudStorageFileSystem extends FileSystem {
   public static final String URI_SCHEME = "gs";
   public static final String GCS_VIEW = "gcs";
   public static final String BASIC_VIEW = "basic";
+  public static final String POSIX_VIEW = "posix";
   public static final int BLOCK_SIZE_DEFAULT = 2 * 1024 * 1024;
   public static final FileTime FILE_TIME_UNKNOWN = FileTime.fromMillis(0);
-  public static final Set<String> SUPPORTED_VIEWS = ImmutableSet.of(BASIC_VIEW, GCS_VIEW);
+  public static final Set<String> SUPPORTED_VIEWS =
+      ImmutableSet.of(BASIC_VIEW, GCS_VIEW, POSIX_VIEW);
   private final CloudStorageFileSystemProvider provider;
   private final String bucket;
   private final CloudStorageConfiguration config;

google-cloud-nio/src/main/java/com/google/cloud/storage/contrib/nio/CloudStorageFileSystemProvider.java

@@ -19,6 +19,12 @@
 import static com.google.common.base.Preconditions.checkArgument;
 import static com.google.common.base.Preconditions.checkNotNull;
 import static com.google.common.base.Strings.isNullOrEmpty;
+import static java.nio.file.attribute.PosixFilePermission.GROUP_EXECUTE;
+import static java.nio.file.attribute.PosixFilePermission.GROUP_READ;
+import static java.nio.file.attribute.PosixFilePermission.GROUP_WRITE;
+import static java.nio.file.attribute.PosixFilePermission.OWNER_EXECUTE;
+import static java.nio.file.attribute.PosixFilePermission.OWNER_READ;
+import static java.nio.file.attribute.PosixFilePermission.OWNER_WRITE;
 
 import com.google.api.gax.paging.Page;
 import com.google.cloud.storage.Acl;
@@ -62,10 +68,13 @@
 import java.nio.file.attribute.BasicFileAttributes;
 import java.nio.file.attribute.FileAttribute;
 import java.nio.file.attribute.FileAttributeView;
+import java.nio.file.attribute.GroupPrincipal;
+import java.nio.file.attribute.UserPrincipal;
 import java.nio.file.spi.FileSystemProvider;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
+import java.util.EnumSet;
 import java.util.HashMap;
 import java.util.Iterator;
 import java.util.List;
@@ -852,7 +861,7 @@ public Map<String, Object> readAttributes(Path path, String attributes, LinkOpti
     //             (eg. BasicFileAttributeView and PosixFileAttributeView), so rather than a partial
     //             implementation we rely on the other overload for now.
 
-    // Partial implementation for a few commonly used ones: basic, gcs
+    // Partial implementation for a few commonly used ones: basic, gcs, posix
     String[] split = attributes.split(":", 2);
     if (split.length != 2) {
       throw new UnsupportedOperationException();
@@ -868,6 +877,9 @@ public Map<String, Object> readAttributes(Path path, String attributes, LinkOpti
       case "gcs":
         fileAttributes = readAttributes(path, CloudStorageFileAttributes.class, options);
         break;
+      case "posix":
+        // There is no real support for posix.
+        // Some systems expect Posix support for everything so these attributes are faked.
       case "basic":
         fileAttributes = readAttributes(path, BasicFileAttributes.class, options);
         break;
@@ -905,6 +917,53 @@ public Map<String, Object> readAttributes(Path path, String attributes, LinkOpti
       results.put("size", fileAttributes.size());
     }
 
+    // There is no real support for posix.
+    // Some systems fail if there is no posix support at all.
+    // To let these systems use this FileSystem these attributes are faked.
+    if (view.equals("posix")) {
+      if (allAttributes || attributeNames.contains("owner")) {
+        results.put(
+            "owner",
+            new UserPrincipal() {
+              @Override
+              public String getName() {
+                return "fakeowner";
+              }
+
+              @Override
+              public String toString() {
+                return "fakeowner";
+              }
+            });
+      }
+      if (allAttributes || attributeNames.contains("group")) {
+        results.put(
+            "group",
+            new GroupPrincipal() {
+              @Override
+              public String getName() {
+                return "fakegroup";
+              }
+
+              @Override
+              public String toString() {
+                return "fakegroup";
+              }
+            });
+      }
+      if (allAttributes || attributeNames.contains("permissions")) {
+        if (fileAttributes.isRegularFile()) {
+          results.put("permissions", EnumSet.of(OWNER_READ, OWNER_WRITE, GROUP_READ, GROUP_WRITE));
+        } else {
+          // Directories, Symlinks and Other:
+          results.put(
+              "permissions",
+              EnumSet.of(
+                  OWNER_READ, OWNER_WRITE, OWNER_EXECUTE, GROUP_READ, GROUP_WRITE, GROUP_EXECUTE));
+        }
+      }
+    }
+
     // CloudStorageFileAttributes
     if (fileAttributes instanceof CloudStorageFileAttributes) {
       CloudStorageFileAttributes cloudStorageFileAttributes =

google-cloud-nio/src/test/java/com/google/cloud/storage/contrib/nio/CloudStorageFileSystemProviderTest.java

@@ -59,6 +59,8 @@
 import java.nio.file.Paths;
 import java.nio.file.attribute.BasicFileAttributes;
 import java.nio.file.attribute.FileTime;
+import java.nio.file.attribute.GroupPrincipal;
+import java.nio.file.attribute.UserPrincipal;
 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
@@ -906,7 +908,51 @@ public void testReadAttributes() throws IOException {
     assertEquals(
         expectedSpecific,
         fileSystemProvider.readAttributes(
-            path1, "basic:lastModifiedTime,isSymbolicLink,isOther,etag,cacheControl"));
+            path1, "basic:lastModifiedTime,isSymbolicLink,isOther,etag,cacheControl,owner,group"));
+
+    // Add the attributes that are only known in posix view
+    // These are all fake values
+    expectedSpecific.put(
+        "owner",
+        new UserPrincipal() {
+          @Override
+          public String getName() {
+            return "fakeowner";
+          }
+
+          @Override
+          public String toString() {
+            return "fakeowner";
+          }
+        });
+
+    expectedSpecific.put(
+        "group",
+        new GroupPrincipal() {
+          @Override
+          public String getName() {
+            return "fakegroup";
+          }
+
+          @Override
+          public String toString() {
+            return "fakegroup";
+          }
+        });
+
+    // The equals between two anonymous classes (the UserPrincipal and GroupPrincipal) is always
+    // false
+    // so we compare the toString() instead.
+    assertEquals(
+        expectedSpecific.toString(),
+        fileSystemProvider
+            .readAttributes(
+                path1,
+                "posix:lastModifiedTime,isSymbolicLink,isOther,etag,cacheControl,owner,group")
+            .toString());
+
+    expectedSpecific.remove("owner");
+    expectedSpecific.remove("group");
 
     // Add the attributes that are only known in gcs view
     expectedSpecific.put("etag", Optional.of("TheEtag"));
@@ -915,7 +961,7 @@ public void testReadAttributes() throws IOException {
     assertEquals(
         expectedSpecific,
         fileSystemProvider.readAttributes(
-            path1, "gcs:lastModifiedTime,isSymbolicLink,isOther,etag,cacheControl"));
+            path1, "gcs:lastModifiedTime,isSymbolicLink,isOther,etag,cacheControl,owner,group"));
   }
 
   private static CloudStorageConfiguration permitEmptyPathComponents(boolean value) {

google-cloud-nio/src/test/java/com/google/cloud/storage/contrib/nio/CloudStorageFileSystemTest.java

@@ -179,7 +179,7 @@ public void testGetters() throws IOException {
       assertThat(fs.getRootDirectories()).containsExactly(fs.getPath("/"));
       assertThat(fs.getFileStores()).isEmpty();
       assertThat(fs.getSeparator()).isEqualTo("/");
-      assertThat(fs.supportedFileAttributeViews()).containsExactly("basic", "gcs");
+      assertThat(fs.supportedFileAttributeViews()).containsExactly("basic", "gcs", "posix");
     }
   }