hugr_core/

envelope.rs

//! Envelope format for HUGR packages.
//!
//! The format is designed to be extensible and backwards-compatible. It
//! consists of a header declaring the format used to encode the HUGR, followed
//! by the encoded HUGR itself.
//!
//! Use [`read_envelope`] and [`write_envelope`] for reading and writing
//! envelopes from/to readers and writers, or call [`Package::load`] and
//! [`Package::store`] directly.
//!
//! ## Payload formats
//!
//! The envelope may encode the HUGR in different formats, listed in
//! [`EnvelopeFormat`]. The payload may also be compressed with zstd.
//!
//! Some formats can be represented as ASCII, as indicated by the
//! [`EnvelopeFormat::ascii_printable`] method. When this is the case, the
//! whole envelope can be stored in a string.
//!
//! ## Envelope header
//!
//! The binary header format is 10 bytes, with the following fields:
//!
//! | Field  | Size (bytes) | Description |
//! |--------|--------------|-------------|
//! | Magic  | 8            | [`MAGIC_NUMBERS`] constant identifying the envelope format. |
//! | Format | 1            | [`EnvelopeFormat`] describing the payload format. |
//! | Flags  | 1            | Additional configuration flags. |
//!
//! Flags:
//!
//! - Bit 0: Whether the payload is compressed with zstd.
//! - Bits 1-5: Reserved for future use.
//! - Bit 7,6: Constant "01" to make some headers ascii-printable.
//!

#![allow(deprecated)]
// TODO: Due to a bug in `derive_more`
// (https://github.com/JelteF/derive_more/issues/419) we need to deactivate
// deprecation warnings here. We can reactivate them once the bug is fixed by
// https://github.com/JelteF/derive_more/pull/454.

mod header;
mod package_json;
pub mod serde_with;

pub use header::{EnvelopeConfig, EnvelopeFormat, MAGIC_NUMBERS, ZstdConfig};
pub use package_json::PackageEncodingError;

use crate::{Hugr, HugrView};
use crate::{
    extension::{ExtensionRegistry, Version},
    package::Package,
};
use header::EnvelopeHeader;
use std::io::BufRead;
use std::io::Write;
use std::str::FromStr;
use thiserror::Error;

#[allow(unused_imports)]
use itertools::Itertools as _;

use crate::import::ImportError;
use crate::{Extension, import::import_package};

/// Key used to store the name of the generator that produced the envelope.
pub const GENERATOR_KEY: &str = "core.generator";
/// Key used to store the list of used extensions in the metadata of a HUGR.
pub const USED_EXTENSIONS_KEY: &str = "core.used_extensions";

/// Get the name of the generator from the metadata of the HUGR modules.
/// If multiple modules have different generators, a comma-separated list is returned in
/// module order.
/// If no generator is found, `None` is returned.
fn get_generator<H: HugrView>(modules: &[H]) -> Option<String> {
    let generators: Vec<String> = modules
        .iter()
        .filter_map(|hugr| hugr.get_metadata(hugr.module_root(), GENERATOR_KEY))
        .map(|v| v.to_string())
        .collect();
    if generators.is_empty() {
        return None;
    }

    Some(generators.join(", "))
}

fn gen_str(generator: &Option<String>) -> String {
    match generator {
        Some(g) => format!("\ngenerated by {g}"),
        None => String::new(),
    }
}

/// Wrap an error with a generator string.
#[derive(Error, Debug)]
#[error("{inner}{}", gen_str(&self.generator))]
pub struct WithGenerator<E: std::fmt::Display> {
    inner: Box<E>,
    /// The name of the generator that produced the envelope, if any.
    generator: Option<String>,
}

impl<E: std::fmt::Display> WithGenerator<E> {
    fn new(err: E, modules: &[impl HugrView]) -> Self {
        Self {
            inner: Box::new(err),
            generator: get_generator(modules),
        }
    }
}

/// Read a HUGR envelope from a reader.
///
/// Returns the deserialized package and the configuration used to encode it.
///
/// Parameters:
/// - `reader`: The reader to read the envelope from.
/// - `registry`: An extension registry with additional extensions to use when
///   decoding the HUGR, if they are not already included in the package.
pub fn read_envelope(
    mut reader: impl BufRead,
    registry: &ExtensionRegistry,
) -> Result<(EnvelopeConfig, Package), EnvelopeError> {
    let header = EnvelopeHeader::read(&mut reader)?;

    let package = match header.zstd {
        #[cfg(feature = "zstd")]
        true => read_impl(
            std::io::BufReader::new(zstd::Decoder::new(reader)?),
            header,
            registry,
        ),
        #[cfg(not(feature = "zstd"))]
        true => Err(EnvelopeError::ZstdUnsupported),
        false => read_impl(reader, header, registry),
    }?;
    Ok((header.config(), package))
}

/// Write a HUGR package into an envelope, using the specified configuration.
///
/// It is recommended to use a buffered writer for better performance.
/// See [`std::io::BufWriter`] for more information.
pub fn write_envelope(
    writer: impl Write,
    package: &Package,
    config: EnvelopeConfig,
) -> Result<(), EnvelopeError> {
    write_envelope_impl(writer, &package.modules, &package.extensions, config)
}

/// Write a deconstructed HUGR package into an envelope, using the specified configuration.
///
/// It is recommended to use a buffered writer for better performance.
/// See [`std::io::BufWriter`] for more information.
pub(crate) fn write_envelope_impl<'h>(
    mut writer: impl Write,
    hugrs: impl IntoIterator<Item = &'h Hugr>,
    extensions: &ExtensionRegistry,
    config: EnvelopeConfig,
) -> Result<(), EnvelopeError> {
    let header = config.make_header();
    header.write(&mut writer)?;

    match config.zstd {
        #[cfg(feature = "zstd")]
        Some(zstd) => {
            let writer = zstd::Encoder::new(writer, zstd.level())?.auto_finish();
            write_impl(writer, hugrs, extensions, config)?;
        }
        #[cfg(not(feature = "zstd"))]
        Some(_) => return Err(EnvelopeError::ZstdUnsupported),
        None => write_impl(writer, hugrs, extensions, config)?,
    }

    Ok(())
}

/// Error type for envelope operations.
#[derive(Debug, Error)]
#[non_exhaustive]
pub enum EnvelopeError {
    /// Bad magic number.
    #[error(
        "Bad magic number. expected 0x{:X} found 0x{:X}",
        u64::from_be_bytes(*expected),
        u64::from_be_bytes(*found)
    )]
    MagicNumber {
        /// The expected magic number.
        ///
        /// See [`MAGIC_NUMBERS`].
        expected: [u8; 8],
        /// The magic number in the envelope.
        found: [u8; 8],
    },
    /// The specified payload format is invalid.
    #[error("Format descriptor {descriptor} is invalid.")]
    InvalidFormatDescriptor {
        /// The unsupported format.
        descriptor: usize,
    },
    /// The specified payload format is not supported.
    #[error("Payload format {format} is not supported.{}",
        match feature {
            Some(f) => format!(" This requires the '{f}' feature for `hugr`."),
            None => String::new()
        },
    )]
    FormatUnsupported {
        /// The unsupported format.
        format: EnvelopeFormat,
        /// Optionally, the feature required to support this format.
        feature: Option<&'static str>,
    },
    /// Not all envelope formats can be represented as ASCII.
    ///
    /// This error is used when trying to store the envelope into a string.
    #[error("Envelope format {format} cannot be represented as ASCII.")]
    NonASCIIFormat {
        /// The unsupported format.
        format: EnvelopeFormat,
    },
    /// Envelope encoding required zstd compression, but the feature is not enabled.
    #[error("Zstd compression is not supported. This requires the 'zstd' feature for `hugr`.")]
    ZstdUnsupported,
    /// Expected the envelope to contain a single HUGR.
    #[error("Expected an envelope containing a single hugr, but it contained {}.", if *count == 0 {
        "none".to_string()
    } else {
        count.to_string()
    })]
    ExpectedSingleHugr {
        /// The number of HUGRs in the package.
        count: usize,
    },
    /// JSON serialization error.
    #[error(transparent)]
    SerdeError {
        /// The source error.
        #[from]
        source: serde_json::Error,
    },
    /// IO read/write error.
    #[error(transparent)]
    IO {
        /// The source error.
        #[from]
        source: std::io::Error,
    },
    /// Error writing a json package to the payload.
    #[error(transparent)]
    PackageEncoding {
        /// The source error.
        #[from]
        source: PackageEncodingError,
    },
    /// Error importing a HUGR from a hugr-model payload.
    #[error(transparent)]
    ModelImport {
        /// The source error.
        #[from]
        source: ImportError,
        // TODO add generator to model import errors
    },
    /// Error reading a HUGR model payload.
    #[error(transparent)]
    ModelRead {
        /// The source error.
        #[from]
        source: hugr_model::v0::binary::ReadError,
    },
    /// Error writing a HUGR model payload.
    #[error(transparent)]
    ModelWrite {
        /// The source error.
        #[from]
        source: hugr_model::v0::binary::WriteError,
    },
    /// Error reading a HUGR model payload.
    #[error(transparent)]
    ModelTextRead {
        /// The source error.
        #[from]
        source: hugr_model::v0::ast::ParseError,
    },
    /// Error reading a HUGR model payload.
    #[error(transparent)]
    ModelTextResolve {
        /// The source error.
        #[from]
        source: hugr_model::v0::ast::ResolveError,
    },
    /// Error reading a list of extensions from the envelope.
    #[error(transparent)]
    ExtensionLoad {
        /// The source error.
        #[from]
        source: crate::extension::ExtensionRegistryLoadError,
    },
}

/// Internal implementation of [`read_envelope`] to call with/without the zstd decompression wrapper.
fn read_impl(
    payload: impl BufRead,
    header: EnvelopeHeader,
    registry: &ExtensionRegistry,
) -> Result<Package, EnvelopeError> {
    match header.format {
        #[allow(deprecated)]
        EnvelopeFormat::PackageJson => Ok(package_json::from_json_reader(payload, registry)?),
        EnvelopeFormat::Model | EnvelopeFormat::ModelWithExtensions => {
            decode_model(payload, registry, header.format)
        }
        EnvelopeFormat::ModelText | EnvelopeFormat::ModelTextWithExtensions => {
            decode_model_ast(payload, registry, header.format)
        }
    }
}

/// Read a HUGR model payload from a reader.
///
/// Parameters:
/// - `stream`: The reader to read the envelope from.
/// - `extension_registry`: An extension registry with additional extensions to use when
///   decoding the HUGR, if they are not already included in the package.
/// - `format`: The format of the payload.
fn decode_model(
    mut stream: impl BufRead,
    extension_registry: &ExtensionRegistry,
    format: EnvelopeFormat,
) -> Result<Package, EnvelopeError> {
    use hugr_model::v0::bumpalo::Bump;

    if format.model_version() != Some(0) {
        return Err(EnvelopeError::FormatUnsupported {
            format,
            feature: None,
        });
    }

    let bump = Bump::default();
    let model_package = hugr_model::v0::binary::read_from_reader(&mut stream, &bump)?;

    let mut extension_registry = extension_registry.clone();
    if format == EnvelopeFormat::ModelWithExtensions {
        let extra_extensions = ExtensionRegistry::load_json(stream, &extension_registry)?;
        extension_registry.extend(extra_extensions);
    }

    Ok(import_package(&model_package, &extension_registry)?)
}

/// Read a HUGR model text payload from a reader.
///
/// Parameters:
/// - `stream`: The reader to read the envelope from.
/// - `extension_registry`: An extension registry with additional extensions to use when
///   decoding the HUGR, if they are not already included in the package.
/// - `format`: The format of the payload.
fn decode_model_ast(
    mut stream: impl BufRead,
    extension_registry: &ExtensionRegistry,
    format: EnvelopeFormat,
) -> Result<Package, EnvelopeError> {
    use crate::import::import_package;
    use hugr_model::v0::bumpalo::Bump;

    if format.model_version() != Some(0) {
        return Err(EnvelopeError::FormatUnsupported {
            format,
            feature: None,
        });
    }

    let mut extension_registry = extension_registry.clone();
    if format == EnvelopeFormat::ModelTextWithExtensions {
        let deserializer = serde_json::Deserializer::from_reader(&mut stream);
        // Deserialize the first json object, leaving the rest of the reader unconsumed.
        let extra_extensions = deserializer
            .into_iter::<Vec<Extension>>()
            .next()
            .unwrap_or(Ok(vec![]))?;
        for ext in extra_extensions {
            extension_registry.register_updated(ext);
        }
    }

    // Read the package into a string, then parse it.
    //
    // Due to how `to_string` works, we cannot append extensions after the package.
    let mut buffer = String::new();
    stream.read_to_string(&mut buffer)?;
    let ast_package = hugr_model::v0::ast::Package::from_str(&buffer)?;

    let bump = Bump::default();
    let model_package = ast_package.resolve(&bump)?;

    Ok(import_package(&model_package, &extension_registry)?)
}

/// Internal implementation of [`write_envelope`] to call with/without the zstd compression wrapper.
fn write_impl<'h>(
    writer: impl Write,
    hugrs: impl IntoIterator<Item = &'h Hugr>,
    extensions: &ExtensionRegistry,
    config: EnvelopeConfig,
) -> Result<(), EnvelopeError> {
    match config.format {
        #[allow(deprecated)]
        EnvelopeFormat::PackageJson => package_json::to_json_writer(hugrs, extensions, writer)?,
        EnvelopeFormat::Model
        | EnvelopeFormat::ModelWithExtensions
        | EnvelopeFormat::ModelText
        | EnvelopeFormat::ModelTextWithExtensions => {
            encode_model(writer, hugrs, extensions, config.format)?;
        }
    }
    Ok(())
}

fn encode_model<'h>(
    mut writer: impl Write,
    hugrs: impl IntoIterator<Item = &'h Hugr>,
    extensions: &ExtensionRegistry,
    format: EnvelopeFormat,
) -> Result<(), EnvelopeError> {
    use hugr_model::v0::{binary::write_to_writer, bumpalo::Bump};

    use crate::export::export_package;

    if format.model_version() != Some(0) {
        return Err(EnvelopeError::FormatUnsupported {
            format,
            feature: None,
        });
    }

    // Prepend extensions for binary model.
    if format == EnvelopeFormat::ModelTextWithExtensions {
        serde_json::to_writer(&mut writer, &extensions.iter().collect_vec())?;
    }

    let bump = Bump::default();
    let model_package = export_package(hugrs, extensions, &bump);

    match format {
        EnvelopeFormat::Model | EnvelopeFormat::ModelWithExtensions => {
            write_to_writer(&model_package, &mut writer)?;
        }
        EnvelopeFormat::ModelText | EnvelopeFormat::ModelTextWithExtensions => {
            let model_package = model_package.as_ast().unwrap();
            writeln!(writer, "{model_package}")?;
        }
        _ => unreachable!(),
    }

    // Append extensions for binary model.
    if format == EnvelopeFormat::ModelWithExtensions {
        serde_json::to_writer(writer, &extensions.iter().collect_vec())?;
    }

    Ok(())
}

#[derive(Debug, Clone, PartialEq, Eq, serde::Deserialize)]
struct UsedExtension {
    name: String,
    version: Version,
}

#[derive(Debug, Error)]
#[error(
    "Extension '{name}' version mismatch: registered version is {registered}, but used version is {used}"
)]
/// Error raised when the reported used version of an extension
/// does not match the registered version in the extension registry.
pub struct ExtensionVersionMismatch {
    name: String,
    registered: Version,
    used: Version,
}

#[derive(Debug, Error)]
#[non_exhaustive]
/// Error raised when checking for breaking changes in used extensions.
pub enum ExtensionBreakingError {
    /// The extension version in the metadata does not match the registered version.
    #[error("{0}")]
    ExtensionVersionMismatch(ExtensionVersionMismatch),

    /// Error deserializing the used extensions metadata.
    #[error("Failed to deserialize used extensions metadata")]
    Deserialization(#[from] serde_json::Error),
}
/// If HUGR metadata contains a list of used extensions, under the key [`USED_EXTENSIONS_KEY`],
/// and extension is registered in the given registry, check that the
/// version of the extension in the metadata matches the registered version (up to
/// MAJOR.MINOR).
fn check_breaking_extensions(
    hugr: impl crate::HugrView,
    registry: &ExtensionRegistry,
) -> Result<(), ExtensionBreakingError> {
    let Some(exts) = hugr.get_metadata(hugr.module_root(), USED_EXTENSIONS_KEY) else {
        return Ok(()); // No used extensions metadata, nothing to check
    };
    let used_exts: Vec<UsedExtension> = serde_json::from_value(exts.clone())?; // TODO handle errors properly

    for ext in used_exts {
        let Some(registered) = registry.get(ext.name.as_str()) else {
            continue; // Extension not registered, ignore
        };
        if !compatible_versions(registered.version(), &ext.version) {
            // This is a breaking change, raise an error.

            return Err(ExtensionBreakingError::ExtensionVersionMismatch(
                ExtensionVersionMismatch {
                    name: ext.name,
                    registered: registered.version().clone(),
                    used: ext.version,
                },
            ));
        }
    }

    Ok(())
}

/// Check if two versions are compatible according to:
/// - Major version must match.
/// - If major version is 0, minor version must match.
fn compatible_versions(v1: &Version, v2: &Version) -> bool {
    if v1.major != v2.major {
        return false; // Major version mismatch
    }

    if v1.major == 0 {
        // For major version 0, we only allow minor version matches
        return v1.minor == v2.minor;
    }

    true
}

#[cfg(test)]
pub(crate) mod test {
    use super::*;
    use cool_asserts::assert_matches;
    use rstest::rstest;
    use std::borrow::Cow;
    use std::io::BufReader;

    use crate::HugrView;
    use crate::builder::test::{multi_module_package, simple_package};
    use crate::extension::{Extension, ExtensionRegistry, Version};
    use crate::extension::{ExtensionId, PRELUDE_REGISTRY};
    use crate::hugr::HugrMut;
    use crate::hugr::test::check_hugr_equality;
    use crate::std_extensions::STD_REG;
    use serde_json::json;
    use std::sync::Arc;

    /// Returns an `ExtensionRegistry` with the extensions from both
    /// sets. Avoids cloning if the first one already contains all
    /// extensions from the second one.
    fn join_extensions<'a>(
        extensions: &'a ExtensionRegistry,
        other: &ExtensionRegistry,
    ) -> Cow<'a, ExtensionRegistry> {
        if other.iter().all(|e| extensions.contains(e.name())) {
            Cow::Borrowed(extensions)
        } else {
            let mut extensions = extensions.clone();
            extensions.extend(other);
            Cow::Owned(extensions)
        }
    }

    /// Serialize and deserialize a HUGR into an envelope with the given config,
    /// and check that the result is the same as the original.
    ///
    /// We do not compare the before and after `Hugr`s for equality directly,
    /// because impls of `CustomConst` are not required to implement equality
    /// checking.
    ///
    /// Returns the deserialized HUGR.
    pub(crate) fn check_hugr_roundtrip(hugr: &Hugr, config: EnvelopeConfig) -> Hugr {
        let mut buffer = Vec::new();
        hugr.store(&mut buffer, config).unwrap();

        let extensions = join_extensions(&STD_REG, hugr.extensions());

        let reader = BufReader::new(buffer.as_slice());
        let extracted = Hugr::load(reader, Some(&extensions)).unwrap();

        check_hugr_equality(&extracted, hugr);
        extracted
    }

    #[rstest]
    fn errors() {
        let package = simple_package();
        assert_matches!(
            package.store_str(EnvelopeConfig::binary()),
            Err(EnvelopeError::NonASCIIFormat { .. })
        );
    }

    #[rstest]
    #[case::empty(Package::default())]
    #[case::simple(simple_package())]
    #[case::multi(multi_module_package())]
    fn text_roundtrip(#[case] package: Package) {
        let envelope = package.store_str(EnvelopeConfig::text()).unwrap();
        let new_package = Package::load_str(&envelope, None).unwrap();
        assert_eq!(package, new_package);
    }

    #[rstest]
    #[case::empty(Package::default())]
    #[case::simple(simple_package())]
    #[case::multi(multi_module_package())]
    #[cfg_attr(all(miri, feature = "zstd"), ignore)] // FFI calls (required to compress with zstd) are not supported in miri
    fn compressed_roundtrip(#[case] package: Package) {
        let mut buffer = Vec::new();
        let config = EnvelopeConfig {
            format: EnvelopeFormat::PackageJson,
            zstd: Some(ZstdConfig::default()),
        };
        let res = package.store(&mut buffer, config);

        match cfg!(feature = "zstd") {
            true => res.unwrap(),
            false => {
                assert_matches!(res, Err(EnvelopeError::ZstdUnsupported));
                return;
            }
        }

        let (decoded_config, new_package) =
            read_envelope(BufReader::new(buffer.as_slice()), &PRELUDE_REGISTRY).unwrap();

        assert_eq!(config.format, decoded_config.format);
        assert_eq!(config.zstd.is_some(), decoded_config.zstd.is_some());
        assert_eq!(package, new_package);
    }

    #[rstest]
    // Empty packages
    #[case::empty_model(Package::default(), EnvelopeFormat::Model)]
    #[case::empty_model_exts(Package::default(), EnvelopeFormat::ModelWithExtensions)]
    #[case::empty_text(Package::default(), EnvelopeFormat::ModelText)]
    #[case::empty_text_exts(Package::default(), EnvelopeFormat::ModelTextWithExtensions)]
    // Single hugrs
    #[case::simple_bin(simple_package(), EnvelopeFormat::Model)]
    #[case::simple_bin_exts(simple_package(), EnvelopeFormat::ModelWithExtensions)]
    #[case::simple_text(simple_package(), EnvelopeFormat::ModelText)]
    #[case::simple_text_exts(simple_package(), EnvelopeFormat::ModelTextWithExtensions)]
    // Multiple hugrs
    #[case::multi_bin(multi_module_package(), EnvelopeFormat::Model)]
    #[case::multi_bin_exts(multi_module_package(), EnvelopeFormat::ModelWithExtensions)]
    #[case::multi_text(multi_module_package(), EnvelopeFormat::ModelText)]
    #[case::multi_text_exts(multi_module_package(), EnvelopeFormat::ModelTextWithExtensions)]
    fn model_roundtrip(#[case] package: Package, #[case] format: EnvelopeFormat) {
        let mut buffer = Vec::new();
        let config = EnvelopeConfig { format, zstd: None };
        package.store(&mut buffer, config).unwrap();

        let (decoded_config, new_package) =
            read_envelope(BufReader::new(buffer.as_slice()), &PRELUDE_REGISTRY).unwrap();

        assert_eq!(config.format, decoded_config.format);
        assert_eq!(config.zstd.is_some(), decoded_config.zstd.is_some());

        assert_eq!(package, new_package);
    }

    #[rstest]
    #[case::simple(simple_package())]
    fn test_check_breaking_extensions(#[case] mut package: Package) {
        // extension with major version 0
        let test_ext_v0 =
            Extension::new(ExtensionId::new_unchecked("test-v0"), Version::new(0, 2, 3));
        //  extension with major version > 0
        let test_ext_v1 =
            Extension::new(ExtensionId::new_unchecked("test-v1"), Version::new(1, 2, 3));

        // Create a registry with the test extensions
        let registry =
            ExtensionRegistry::new([Arc::new(test_ext_v0.clone()), Arc::new(test_ext_v1.clone())]);
        let mut hugr = package.modules.remove(0);

        // No metadata - should pass
        assert_matches!(check_breaking_extensions(&hugr, &registry), Ok(()));

        // Matching version for v0 - should pass
        let used_exts = json!([{ "name": "test-v0", "version": "0.2.3" }]);
        hugr.set_metadata(hugr.module_root(), USED_EXTENSIONS_KEY, used_exts);
        assert_matches!(check_breaking_extensions(&hugr, &registry), Ok(()));

        // Matching major/minor but different patch for v0 - should pass
        let used_exts = json!([{ "name": "test-v0", "version": "0.2.4" }]);
        hugr.set_metadata(hugr.module_root(), USED_EXTENSIONS_KEY, used_exts);
        assert_matches!(check_breaking_extensions(&hugr, &registry), Ok(()));

        //Different minor version for v0 - should fail
        let used_exts = json!([{ "name": "test-v0", "version": "0.3.3" }]);
        hugr.set_metadata(hugr.module_root(), USED_EXTENSIONS_KEY, used_exts);
        assert_matches!(
            check_breaking_extensions(&hugr, &registry),
            Err(ExtensionBreakingError::ExtensionVersionMismatch(ExtensionVersionMismatch {
                name,
                registered,
                used
            })) if name == "test-v0" && registered == Version::new(0, 2, 3) && used == Version::new(0, 3, 3)
        );

        // Different major version for v0 - should fail
        let used_exts = json!([{ "name": "test-v0", "version": "1.2.3" }]);
        hugr.set_metadata(hugr.module_root(), USED_EXTENSIONS_KEY, used_exts);
        assert_matches!(
            check_breaking_extensions(&hugr, &registry),
            Err(ExtensionBreakingError::ExtensionVersionMismatch(ExtensionVersionMismatch {
                name,
                registered,
                used
            })) if name == "test-v0" && registered == Version::new(0, 2, 3) && used == Version::new(1, 2, 3)
        );

        // Matching version for v1 - should pass
        let used_exts = json!([{ "name": "test-v1", "version": "1.2.3" }]);
        hugr.set_metadata(hugr.module_root(), USED_EXTENSIONS_KEY, used_exts);
        assert_matches!(check_breaking_extensions(&hugr, &registry), Ok(()));

        // Different minor version for v1 - should pass
        let used_exts = json!([{ "name": "test-v1", "version": "1.3.0" }]);
        hugr.set_metadata(hugr.module_root(), USED_EXTENSIONS_KEY, used_exts);
        assert_matches!(check_breaking_extensions(&hugr, &registry), Ok(()));

        // Different patch for v1 - should pass
        let used_exts = json!([{ "name": "test-v1", "version": "1.2.4" }]);
        hugr.set_metadata(hugr.module_root(), USED_EXTENSIONS_KEY, used_exts);
        assert_matches!(check_breaking_extensions(&hugr, &registry), Ok(()));

        // Different major version for v1 - should fail
        let used_exts = json!([{ "name": "test-v1", "version": "2.2.3" }]);
        hugr.set_metadata(hugr.module_root(), USED_EXTENSIONS_KEY, used_exts);
        assert_matches!(
            check_breaking_extensions(&hugr, &registry),
            Err(ExtensionBreakingError::ExtensionVersionMismatch(ExtensionVersionMismatch {
                name,
                registered,
                used
            })) if name == "test-v1" && registered == Version::new(1, 2, 3) && used == Version::new(2, 2, 3)
        );

        // Non-registered extension - should pass
        let used_exts = json!([{ "name": "unknown", "version": "1.0.0" }]);
        hugr.set_metadata(hugr.module_root(), USED_EXTENSIONS_KEY, used_exts);
        assert_matches!(check_breaking_extensions(&hugr, &registry), Ok(()));

        // Multiple extensions - one mismatch should fail
        let used_exts = json!([
            { "name": "unknown", "version": "1.0.0" },
            { "name": "test-v1", "version": "2.0.0" }
        ]);
        hugr.set_metadata(hugr.module_root(), USED_EXTENSIONS_KEY, used_exts);
        assert_matches!(
            check_breaking_extensions(&hugr, &registry),
            Err(ExtensionBreakingError::ExtensionVersionMismatch(ExtensionVersionMismatch {
                name,
                registered,
                used
            })) if name == "test-v1" && registered == Version::new(1, 2, 3) && used == Version::new(2, 0, 0)
        );

        // Invalid metadata format - should fail with deserialization error
        hugr.set_metadata(
            hugr.module_root(),
            USED_EXTENSIONS_KEY,
            json!("not an array"),
        );
        assert_matches!(
            check_breaking_extensions(&hugr, &registry),
            Err(ExtensionBreakingError::Deserialization(_))
        );

        //  Multiple extensions with all compatible versions - should pass
        let used_exts = json!([
            { "name": "test-v0", "version": "0.2.5" },
            { "name": "test-v1", "version": "1.9.9" }
        ]);
        hugr.set_metadata(hugr.module_root(), USED_EXTENSIONS_KEY, used_exts);
        assert_matches!(check_breaking_extensions(&hugr, &registry), Ok(()));
    }

    #[test]
    fn test_with_generator_error_message() {
        let test_ext = Extension::new(ExtensionId::new_unchecked("test"), Version::new(1, 0, 0));
        let registry = ExtensionRegistry::new([Arc::new(test_ext)]);

        let mut hugr = simple_package().modules.remove(0);

        // Set a generator name in the metadata
        let generator_name = json!({ "name": "TestGenerator", "version": "1.2.3" });
        hugr.set_metadata(hugr.module_root(), GENERATOR_KEY, generator_name.clone());

        // Set incompatible extension version in metadata
        let used_exts = json!([{ "name": "test", "version": "2.0.0" }]);
        hugr.set_metadata(hugr.module_root(), USED_EXTENSIONS_KEY, used_exts);

        // Create the error and wrap it with WithGenerator
        let err = check_breaking_extensions(&hugr, &registry).unwrap_err();
        let with_gen = WithGenerator::new(err, &[&hugr]);

        let err_msg = with_gen.to_string();
        assert!(err_msg.contains("Extension 'test' version mismatch"));
        assert!(err_msg.contains(generator_name.to_string().as_str()));
    }
}