seanmonstar/warp · error

error reading file ( )

Error message

error reading file ({:?}): {}

What it means

The TLS LazyFile wrapper converts any I/O error from reading the certificate/key file into an io::Error whose message embeds the file path: 'error reading file ("path"): <os error>'. It surfaces underlying failures like missing files or permission problems during TLS server setup.

Solutions

1. Verify the cert/key paths are absolute and the files exist (ls -l) before starting
2. Fix file permissions or run the service as a user that can read the certs
3. Correct relative paths or set the expected working directory in your deployment

Example fix

// before
tls().cert_path("certs/server.pem")
// after
tls().cert_path("/etc/ssl/certs/server.pem") // absolute, verified path

for p in [&cert_path, &key_path] {
    assert!(std::path::Path::new(p).is_file(), "TLS file missing/unreadable: {}", p);
}

fn readable_file(p: &str) -> Option<std::path::PathBuf> {
    let path = std::path::PathBuf::from(p);
    std::fs::File::open(&path).ok().map(|_| path)
}

// LazyFile::read yields io::Error; match on kind()
match std::fs::read(cert_path) {
    Err(e) if e.kind() == std::io::ErrorKind::NotFound => eprintln!("cert missing: {}", cert_path),
    Err(e) => eprintln!("tls read failed: {}", e),
    Ok(_) => {},
}

When it happens

Trigger: tls().cert_path("missing.pem") or key_path pointing to a nonexistent, unreadable, or directory path — the error fires when the lazy file is first read.

Common situations: Wrong working directory so relative paths don't resolve; certs not deployed to the container; file permissions denied for the service user; typo'd paths in config.

Understand the failure class

Background: "failed to read file", EACCES, ENOENT and "could not read <path>" errors: when a program can't read a file from disk — this error's family across 49 libraries.

AI-assisted analysis of seanmonstar/warp@ff34d7213e (2026-09-09). Data as JSON: /api/errors/1ab271d71fa6315d. Report an issue: GitHub.

Appendix: source

Thrown at src/tls.rs:275

    path: PathBuf,
    file: Option<File>,
}

impl LazyFile {
    fn lazy_read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
        if self.file.is_none() {
            self.file = Some(File::open(&self.path)?);
        }

        self.file.as_mut().unwrap().read(buf)
    }
}

impl Read for LazyFile {
    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
        self.lazy_read(buf).map_err(|err| {
            let kind = err.kind();
            io::Error::new(
                kind,
                format!("error reading file ({:?}): {}", self.path.display(), err),
            )
        })
    }
}

impl Transport for TlsStream {
    fn remote_addr(&self) -> Option<SocketAddr> {
        Some(self.remote_addr)
    }
}

enum State {
    Handshaking(tokio_rustls::Accept<AddrStream>),
    Streaming(tokio_rustls::server::TlsStream<AddrStream>),
}

View on GitHub (pinned to ff34d7213e)