oracle/graal · error · UnsupportedOperationException

view <{}> is not supported

Error message

view <{}> is not supported

What it means

Thrown by the private TruffleFileSystemProvider.getFileAttributeView(TrufflePath, String, ...) when the requested file-attribute-view name is anything other than 'basic'. The Truffle file system implements only the basic view; posix, unix, dos, owner, acl, and user views have no native backing. It is reached from readAttributes(Path, String, ...) where the view is the prefix before ':' in the attribute string.

Source

Thrown at espresso/src/com.oracle.truffle.espresso.io/src/sun/nio/fs/TruffleFileSystemProvider.java:317

        return (V) new TruffleBasicFileAttributeView(TrufflePath.toTrufflePath(path), TrufflePath.followLinks(options));
    }

    @Override
    @SuppressWarnings("unchecked")
    public <A extends BasicFileAttributes> A readAttributes(Path path, Class<A> type, LinkOption... options) throws IOException {
        Objects.requireNonNull(type);
        if (type != BasicFileAttributes.class) {
            throw new UnsupportedOperationException();
        }
        return (A) getFileAttributeView(path, BasicFileAttributeView.class, options).readAttributes();
    }

    private TruffleBasicFileAttributeView getFileAttributeView(TrufflePath path, String type, LinkOption... options) {
        Objects.requireNonNull(type);
        if ("basic".equals(type)) {
            return (TruffleBasicFileAttributeView) getFileAttributeView(path, BasicFileAttributeView.class, options);
        }
        throw new UnsupportedOperationException("view <" + type + "> is not supported");
    }

    @Override
    public Map<String, Object> readAttributes(Path path, String attributes, LinkOption... options) throws IOException {
        String view;
        String attrs;
        int colonPos = attributes.indexOf(':');
        if (colonPos == -1) {
            view = "basic";
            attrs = attributes;
        } else {
            view = attributes.substring(0, colonPos++);
            attrs = attributes.substring(colonPos);
        }
        return getFileAttributeView(TrufflePath.toTrufflePath(path), view, options).readAttributes(attrs);
    }

    @Override

View on GitHub (pinned to a66e9ccd1d)

Solutions

1. Use the basic view: Files.readAttributes(path, "basic:*") or BasicFileAttributes.class
2. Guard with path.getFileSystem().supportedFileAttributeViews().contains("posix") before requesting posix attributes
3. Wrap posix queries in try/catch UnsupportedOperationException and fall back to basic attributes

Example fix

// before
PosixFileAttributes attrs = Files.readAttributes(path, PosixFileAttributes.class);

// after
BasicFileAttributes attrs;
if (path.getFileSystem().supportedFileAttributeViews().contains("posix")) {
    attrs = Files.readAttributes(path, PosixFileAttributes.class);
} else {
    attrs = Files.readAttributes(path, BasicFileAttributes.class);
}

Set<String> views = path.getFileSystem().supportedFileAttributeViews();
String view = attributes.contains(":") ? attributes.substring(0, attributes.indexOf(':')) : "basic";
if (!views.contains(view)) {
    attributes = "basic:lastModifiedTime,lastAccessTime,creationTime,size,isDirectory,isRegularFile";
}

catch (UnsupportedOperationException e) { fall back to Files.readAttributes(path, BasicFileAttributes.class); }

When it happens

Trigger: Files.readAttributes(path, "posix:*"), readAttributes(path, "unix:size,lastModifiedTime", ...), or Files.getAttribute(path, "owner:owner") on a TrufflePath. Also Files.getPosixFileAttributes/Files.getFileAttributeView(path, PosixFileAttributeView.class) paths that funnel through the string form.

Common situations: Porting POSIX file code (permissions, uid/gid queries) to run inside an Espresso guest on Windows or on a host where only basic attributes are bridged; libraries like Apache Commons IO or sshd that query posix views unconditionally.

Related errors

• file attributes: {attrs}
• '{}' is unknown or read-only attribute
• Path component is undefined
• Path component should be '/'
• Query component present

AI-assisted analysis of oracle/graal@a66e9ccd1d (2026-08-14). Data as JSON: /api/errors/005a91c6b19f6f16. Report an issue: GitHub.