Function load_toml_file

src/agents/mod.rs:1407–1427

Load a TOML file as a document. Returns an empty table when the file does not exist. When the file exists but cannot be parsed as a TOML document, returns a [`TraceDecayError::Config`] so callers do not silently overwrite the user's data (see issue #63).

(path: &Path)

/// but cannot be parsed as a TOML document, returns a [`TraceDecayError::Config`]
/// so callers do not silently overwrite the user's data (see issue #63).
pub fn load_toml_file(path: &Path) -> Result<toml::Value> {
    if !path.exists() {
        return Ok(toml::Value::Table(toml::map::Map::new()));
    }
    let contents = std::fs::read_to_string(path).map_err(|e| TraceDecayError::Config {
        message: format!("failed to read {}: {e}", path.display()),
    })?;
    if contents.trim().is_empty() {
        return Ok(toml::Value::Table(toml::map::Map::new()));
    }
    // NOTE: `str.parse::<toml::Value>()` parses a single TOML value in toml v1,
    // not a document — using it here would treat any well-formed config.toml as
    // unparseable and silently drop its contents. Use `toml::from_str` instead.
    let table: toml::Table = toml::from_str(&contents).map_err(|e| TraceDecayError::Config {
        message: format!(
            "failed to parse {} as TOML: {e}. Refusing to overwrite — fix the file or remove it manually.",
            path.display()
        ),
    })?;
    Ok(toml::Value::Table(table))
}

/// Copy `path` to `<path>.bak` if it exists. Used before overwriting a user
/// config so an unexpected change is recoverable (issue #63).