linera-io/linera-protocol · error

could not parse OS string into string: {}

Error message

could not parse OS string into string: {}

What it means

A filesystem path that must be returned as a String contains bytes that are not valid UTF-8. On Unix, paths are arbitrary byte strings; OsString::into_string() enforces UTF-8, so a temp dir or parent directory with non-UTF-8 bytes (odd locale filenames, corrupted names) makes the test-net config writer fail.

Source

Thrown at linera-service/src/cli_wrappers/local_net.rs:698

                    let host = exporter.host.clone();
                    let port = exporter.port;
                    let config_content = format!(
                        r#"

                        [[block_exporters]]
                        host = "{host}"
                        port = {port}
                        "#
                    );

                    content.push_str(&config_content);
                }
            }
        }

        fs_err::write(&path, content)?;
        path.into_os_string().into_string().map_err(|error| {
            anyhow!(
                "could not parse OS string into string: {}",
                error.to_string_lossy()
            )
        })
    }

    fn generate_block_exporter_config(
        &self,
        validator: usize,
        exporter_id: u32,
        destination_config: &DestinationConfig,
    ) -> String {
        let n = validator;
        let host = Network::Grpc.localhost();
        let port = self.block_exporter_port(n, exporter_id as usize);
        let metrics_port = Self::block_exporter_metrics_port(exporter_id as usize);
        let mut config = format!(
            r#"

View on GitHub (pinned to 6c226ddcb3)

Solutions

1. Set TMPDIR (and CARGO_TARGET_TMPDIR for Rust test tempdirs) to a clean UTF-8 path.
2. Run the test suite from a checkout whose full path is valid UTF-8.
3. Rename the offending directory.
4. In library code, avoid the conversion: return/keep PathBuf, or use to_str() with an actionable error.

Example fix

// before: hard failure on non-UTF-8 path bytes
path.into_os_string().into_string().map_err(|error| {
    anyhow!("could not parse OS string into string: {}", error.to_string_lossy())
})?

// after: keep the PathBuf — no UTF-8 requirement is actually needed
Ok(path) // callers use it as a path, not as a String

if path.to_str().is_none() {
    anyhow::bail!(
        "path {:#?} is not valid UTF-8 — set TMPDIR to a UTF-8 directory",
        path.display()
    );
}

fn is_utf8_path(p: &std::path::Path) -> bool {
    p.to_str().is_some()
}

When it happens

Trigger: local_net's configuration_string writes the validator config to a path derived from the temp/config directory, then converts it via into_string(); TMPDIR, CARGO_TARGET_TMPDIR, or the repo path containing non-UTF-8 bytes triggers the error.

Common situations: CI images or mount points with legacy-encoding directory names; a TMPDIR set from a misconfigured shell; filenames mangled during archive extraction across systems.

Related errors

• Expected an `ExecutionError`. Got: {self:#?}
• Expected an `ExecutionError`. Got: {chain_error:#?}
• Failed to obtain a port
• Notification subscription failed: {errors:?}
• Query result subscription failed: {errors:?}

AI-assisted analysis of linera-io/linera-protocol@6c226ddcb3 (2026-08-22). Data as JSON: /api/errors/9932b61f8f914ff6. Report an issue: GitHub.