MuntashirAkon/AppManager · error · IllegalArgumentException

Display name contains file separator.

Error message

Display name contains file separator.

What it means

findOrCreateFile() requires a single-segment display name; if the sanitized name still contains the file separator character it throws IllegalArgumentException("Display name contains file separator."). Nested paths must be created level by level. This is a path-traversal/nesting guard.

Source

Thrown at app/src/main/java/io/github/muntashirakon/io/PathImpl.java:484

    }

    @NonNull
    public Path findFile(@NonNull String displayName) throws FileNotFoundException {
        DocumentFile nextPath = findFileInternal(documentFile, displayName);
        if (nextPath == null) {
            throw new FileNotFoundException("Cannot find " + this + File.separatorChar + displayName);
        }
        return new PathImpl(context, nextPath);
    }

    @NonNull
    public Path findOrCreateFile(@NonNull String displayName, @Nullable String mimeType) throws IOException {
        displayName = Paths.sanitize(displayName, true);
        if (displayName == null) {
            throw new IOException("Empty display name.");
        }
        if (displayName.indexOf(File.separatorChar) != -1) {
            throw new IllegalArgumentException("Display name contains file separator.");
        }
        DocumentFile documentFile = getRealDocumentFile(this.documentFile);
        if (!documentFile.isDirectory()) {
            throw new IOException("Current file is not a directory.");
        }
        String extension = null;
        if (mimeType != null) {
            extension = MimeTypeMap.getSingleton().getExtensionFromMimeType(mimeType);
        } else mimeType = DEFAULT_MIME;
        String nameWithExtension = displayName + (extension != null ? "." + extension : "");
        checkVfs(Paths.appendPathSegment(documentFile.getUri(), nameWithExtension));
        DocumentFile file = documentFile.findFile(displayName);
        if (file != null) {
            if (file.isDirectory()) {
                throw new IOException("Directory cannot be converted to file");
            }
            return new PathImpl(context, file);
        }

View on GitHub (pinned to 0152f468fc)

Solutions

1. Extract only the final segment (substring after last separator) before calling.
2. Create intermediate directories with createDirectories/findOrCreateDirectory first, then findOrCreateFile on the leaf name.
3. Replace or reject separator characters in user-derived filenames at input time.
4. Use Paths helpers to split the path rather than manual string handling.

Example fix

// before
path.findOrCreateFile("sub/dir/file.txt", mime); // IllegalArgumentException
// after
path.createDirectories("sub/dir");
path.findOrCreateDirectory("dir"); // on the sub Path
String leaf = new File("sub/dir/file.txt").getName();
leafPath.findOrCreateFile(leaf, mime);

if (displayName.indexOf(File.separatorChar) != -1) {
    throw new IllegalArgumentException("Expected a single-segment file name: " + displayName);
}

boolean isSingleSegment(String n) { return n != null && n.indexOf(File.separatorChar) == -1; }

try { dir.findOrCreateFile(name, mime); } catch (IllegalArgumentException e) { /* split path, create dirs, retry on leaf */ }

When it happens

Trigger: Calling findOrCreateFile with names like "sub/dir/file.txt" or an absolute path "/data/file.txt" — anything containing File.separatorChar after sanitization.

Common situations: Passing a full path where only a filename is expected (common when reusing Path handling code); joining base dir and filename with "/" yourself; names taken from URLs containing slashes.

Understand the failure class

Background: "Must be a positive integer", "Invalid value", "Unsupported": the invalid-argument-value error family, when a library rejects the value you pass — this error's family across 35 libraries.

Related errors

• Display name is empty
• Couldn't find any writable Obb dir
• Could not delete the selected backups
• Data directory cannot be empty.
• Could not create package staging directory

AI-assisted analysis of MuntashirAkon/AppManager@0152f468fc (2026-09-12). Data as JSON: /api/errors/769bbdafe54d6754. Report an issue: GitHub.