polyvers 0.1.2

//! Single-macro schema versioning. See the crate README for the canonical
//! example and rationale.

pub use polyvers_macros::versioned;

/// Errors returned by the generated `parse_at_version` function.
#[derive(Debug, thiserror::Error)]
#[non_exhaustive]
pub enum Error {
    /// The requested version string did not match any declared version.
    #[error("unknown version `{requested}`; known versions: {known:?}")]
    UnknownVersion {
        requested: String,
        known: &'static [&'static str],
    },
    /// The underlying serde format failed to parse the input.
    #[error("format error: {0}")]
    Format(Box<dyn std::error::Error + Send + Sync>),
}

impl Error {
    /// Construct an `UnknownVersion` error. Used by generated code.
    pub fn unknown_version(requested: &str, known: &'static [&'static str]) -> Self {
        Self::UnknownVersion {
            requested: requested.to_owned(),
            known,
        }
    }

    /// Wrap any `std::error::Error` as a `Format` variant. Used by generated code.
    pub fn format<E>(err: E) -> Self
    where
        E: std::error::Error + Send + Sync + 'static,
    {
        Self::Format(Box::new(err))
    }

    /// Wrap any displayable value as a `Format` variant. Used by generated
    /// code for codecs whose error types do not implement `std::error::Error`
    /// (notably some `rkyv` 0.7 validation errors).
    pub fn format_str<S: Into<String>>(message: S) -> Self {
        #[derive(Debug)]
        struct StringError(String);
        impl std::fmt::Display for StringError {
            fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
                f.write_str(&self.0)
            }
        }
        impl std::error::Error for StringError {}
        Self::Format(Box::new(StringError(message.into())))
    }
}