typify_impl/

lib.rs

// Copyright 2025 Oxide Computer Company

//! typify backend implementation.

#![deny(missing_docs)]

use std::collections::{BTreeMap, BTreeSet};

use conversions::SchemaCache;
use log::info;
use output::OutputSpace;
use proc_macro2::TokenStream;
use quote::{format_ident, quote, ToTokens};
use schemars::schema::{Metadata, RootSchema, Schema};
use thiserror::Error;
use type_entry::{
    StructPropertyState, TypeEntry, TypeEntryDetails, TypeEntryNative, TypeEntryNewtype,
    WrappedValue,
};

use crate::util::{sanitize, Case};

pub use crate::util::accept_as_ident;

#[cfg(test)]
mod test_util;

mod conversions;
mod convert;
mod cycles;
mod defaults;
mod enums;
mod merge;
mod output;
mod rust_extension;
mod structs;
mod type_entry;
mod util;
mod validate;
mod value;

#[allow(missing_docs)]
#[derive(Error, Debug)]
pub enum Error {
    #[error("unexpected value type")]
    BadValue(String, serde_json::Value),
    #[error("invalid TypeId")]
    InvalidTypeId,
    #[error("value does not conform to the given schema")]
    InvalidValue,
    #[error("invalid schema for {}: {reason}", show_type_name(.type_name.as_deref()))]
    InvalidSchema {
        type_name: Option<String>,
        reason: String,
    },
}

impl Error {
    fn invalid_value() -> Self {
        Self::InvalidValue
    }
}

#[allow(missing_docs)]
pub type Result<T> = std::result::Result<T, Error>;

fn show_type_name(type_name: Option<&str>) -> &str {
    type_name.unwrap_or("<unknown type>")
}

/// Representation of a type which may have a definition or may be built-in.
#[derive(Debug)]
pub struct Type<'a> {
    type_space: &'a TypeSpace,
    type_entry: &'a TypeEntry,
}

#[allow(missing_docs)]
/// Type details returned by Type::details() to inspect a type.
pub enum TypeDetails<'a> {
    Enum(TypeEnum<'a>),
    Struct(TypeStruct<'a>),
    Newtype(TypeNewtype<'a>),

    Option(TypeId),
    Vec(TypeId),
    Map(TypeId, TypeId),
    Set(TypeId),
    Box(TypeId),
    Tuple(Box<dyn Iterator<Item = TypeId> + 'a>),
    Array(TypeId, usize),
    Builtin(&'a str),

    Unit,
    String,
}

/// Enum type details.
pub struct TypeEnum<'a> {
    details: &'a type_entry::TypeEntryEnum,
}

/// Enum variant details.
pub enum TypeEnumVariant<'a> {
    /// Variant with no associated data.
    Simple,
    /// Tuple-type variant with at least one associated type.
    Tuple(Vec<TypeId>),
    /// Struct-type variant with named properties and types.
    Struct(Vec<(&'a str, TypeId)>),
}

/// Full information pertaining to an enum variant.
pub struct TypeEnumVariantInfo<'a> {
    /// Name.
    pub name: &'a str,
    /// Description.
    pub description: Option<&'a str>,
    /// Details for the enum variant.
    pub details: TypeEnumVariant<'a>,
}

/// Struct type details.
pub struct TypeStruct<'a> {
    details: &'a type_entry::TypeEntryStruct,
}

/// Full information pertaining to a struct property.
pub struct TypeStructPropInfo<'a> {
    /// Name.
    pub name: &'a str,
    /// Description.
    pub description: Option<&'a str>,
    /// Whether the propertty is required.
    pub required: bool,
    /// Identifies the schema for the property.
    pub type_id: TypeId,
}

/// Newtype details.
pub struct TypeNewtype<'a> {
    details: &'a type_entry::TypeEntryNewtype,
}

/// Type identifier returned from type creation and used to lookup types.
#[derive(Debug, PartialEq, PartialOrd, Ord, Eq, Clone, Hash)]
pub struct TypeId(u64);

#[derive(Debug, Clone, PartialEq)]
pub(crate) enum Name {
    Required(String),
    Suggested(String),
    Unknown,
}

impl Name {
    pub fn into_option(self) -> Option<String> {
        match self {
            Name::Required(s) | Name::Suggested(s) => Some(s),
            Name::Unknown => None,
        }
    }

    pub fn append(&self, s: &str) -> Self {
        match self {
            Name::Required(prefix) | Name::Suggested(prefix) => {
                Self::Suggested(format!("{}_{}", prefix, s))
            }
            Name::Unknown => Name::Unknown,
        }
    }
}

#[derive(Debug, Clone, Eq, PartialEq, Ord, PartialOrd)]
pub(crate) enum RefKey {
    Root,
    Def(String),
}

/// A collection of types.
#[derive(Debug)]
pub struct TypeSpace {
    next_id: u64,

    // TODO we need this in order to inspect the collection of reference types
    // e.g. to do `all_mutually_exclusive`. In the future, we could obviate the
    // need this by keeping a single Map of referenced types whose value was an
    // enum of a "raw" or a "converted" schema.
    definitions: BTreeMap<RefKey, Schema>,

    id_to_entry: BTreeMap<TypeId, TypeEntry>,
    type_to_id: BTreeMap<TypeEntryDetails, TypeId>,

    name_to_id: BTreeMap<String, TypeId>,
    ref_to_id: BTreeMap<RefKey, TypeId>,

    uses_chrono: bool,
    uses_uuid: bool,
    uses_serde_json: bool,
    uses_regress: bool,

    settings: TypeSpaceSettings,

    cache: SchemaCache,

    // Shared functions for generating default values
    defaults: BTreeSet<DefaultImpl>,
}

impl Default for TypeSpace {
    fn default() -> Self {
        Self {
            next_id: 1,
            definitions: Default::default(),
            id_to_entry: Default::default(),
            type_to_id: Default::default(),
            name_to_id: Default::default(),
            ref_to_id: Default::default(),
            uses_chrono: Default::default(),
            uses_uuid: Default::default(),
            uses_serde_json: Default::default(),
            uses_regress: Default::default(),
            settings: Default::default(),
            cache: Default::default(),
            defaults: Default::default(),
        }
    }
}

#[derive(Debug, PartialEq, Eq, PartialOrd, Ord)]
pub(crate) enum DefaultImpl {
    Boolean,
    I64,
    U64,
    NZU64,
}

/// Type name to use in generated code.
#[derive(Clone)]
pub struct MapType(pub syn::Type);

impl MapType {
    /// Create a new MapType from a [`str`].
    pub fn new(s: &str) -> Self {
        let map_type = syn::parse_str::<syn::Type>(s).expect("valid ident");
        Self(map_type)
    }
}

impl Default for MapType {
    fn default() -> Self {
        Self::new("::std::collections::HashMap")
    }
}

impl std::fmt::Debug for MapType {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "MapType({})", self.0.to_token_stream())
    }
}

impl std::fmt::Display for MapType {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        self.0.to_token_stream().fmt(f)
    }
}

impl<'de> serde::Deserialize<'de> for MapType {
    fn deserialize<D>(deserializer: D) -> std::result::Result<Self, D::Error>
    where
        D: serde::Deserializer<'de>,
    {
        let s = <&str>::deserialize(deserializer)?;
        Ok(Self::new(s))
    }
}

impl From<String> for MapType {
    fn from(s: String) -> Self {
        Self::new(&s)
    }
}

impl From<&str> for MapType {
    fn from(s: &str) -> Self {
        Self::new(s)
    }
}

impl From<syn::Type> for MapType {
    fn from(t: syn::Type) -> Self {
        Self(t)
    }
}

/// Settings that alter type generation.
#[derive(Default, Debug, Clone)]
pub struct TypeSpaceSettings {
    type_mod: Option<String>,
    extra_derives: Vec<String>,
    extra_attrs: Vec<String>,
    struct_builder: bool,

    unknown_crates: UnknownPolicy,
    crates: BTreeMap<String, CrateSpec>,
    map_type: MapType,

    patch: BTreeMap<String, TypeSpacePatch>,
    replace: BTreeMap<String, TypeSpaceReplace>,
    convert: Vec<TypeSpaceConversion>,
}

#[derive(Debug, Clone)]
struct CrateSpec {
    version: CrateVers,
    rename: Option<String>,
}

/// Policy to apply to external types described by schema extensions whose
/// crates are not explicitly specified.
#[derive(Default, Debug, Clone, Copy, Eq, PartialEq, serde::Deserialize)]
pub enum UnknownPolicy {
    /// Generate the type rather according to the schema.
    #[default]
    Generate,
    /// Use the specified type by path (this will result in a compile error if
    /// one of the crates is not an existing dependency). Note that this
    /// ignores compatibility requirements specified by the schema extension
    /// and may result in subtle failures if the crate used is incompatible
    /// with the version that produced the schema.
    Allow,
    /// If an unknown crate is encountered, generate a compiler warning
    /// indicating the crate that must be specified to proceed along with
    /// version constraints. This affords users an opportunity to specify the
    /// specific crate version to use (or the user may explicitly deny use of
    /// that crate).
    Deny,
}

/// Specify the version for a named crate to consider for type use (rather than
/// generating types) in the presense of a schema extension.
#[derive(Debug, Clone)]
pub enum CrateVers {
    /// An explicit version.
    Version(semver::Version),
    /// Any version.
    Any,
    /// Never use the given crate.
    Never,
}

impl CrateVers {
    /// Parse from a string
    pub fn parse(s: &str) -> Option<Self> {
        if s == "!" {
            Some(Self::Never)
        } else if s == "*" {
            Some(Self::Any)
        } else {
            Some(Self::Version(semver::Version::parse(s).ok()?))
        }
    }
}

/// Contains a set of modifications that may be applied to an existing type.
#[derive(Debug, Default, Clone)]
pub struct TypeSpacePatch {
    rename: Option<String>,
    derives: Vec<String>,
    attrs: Vec<String>,
}

/// Contains the attributes of a replacement of an existing type.
#[derive(Debug, Default, Clone)]
pub struct TypeSpaceReplace {
    replace_type: String,
    impls: Vec<TypeSpaceImpl>,
}

/// Defines a schema which will be replaced, and the attributes of the
/// replacement.
#[derive(Debug, Clone)]
struct TypeSpaceConversion {
    schema: schemars::schema::SchemaObject,
    type_name: String,
    impls: Vec<TypeSpaceImpl>,
}

#[allow(missing_docs)]
// TODO we can currently only address traits for which cycle analysis is not
// required.
#[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
#[non_exhaustive]
pub enum TypeSpaceImpl {
    FromStr,
    FromStringIrrefutable,
    Display,
    Default,
}

impl std::str::FromStr for TypeSpaceImpl {
    type Err = String;

    fn from_str(s: &str) -> std::result::Result<Self, Self::Err> {
        match s {
            "FromStr" => Ok(Self::FromStr),
            "Display" => Ok(Self::Display),
            "Default" => Ok(Self::Default),
            _ => Err(format!("{} is not a valid trait specifier", s)),
        }
    }
}

impl TypeSpaceSettings {
    /// Set the name of the path prefix for types defined in this [TypeSpace].
    pub fn with_type_mod<S: AsRef<str>>(&mut self, type_mod: S) -> &mut Self {
        self.type_mod = Some(type_mod.as_ref().to_string());
        self
    }

    /// Add an additional derive macro to apply to all defined types.
    pub fn with_derive(&mut self, derive: String) -> &mut Self {
        if !self.extra_derives.contains(&derive) {
            self.extra_derives.push(derive);
        }
        self
    }

    /// Add an additional attribute to apply to all defined types.
    pub fn with_attr(&mut self, attr: String) -> &mut Self {
        if !self.extra_attrs.contains(&attr) {
            self.extra_attrs.push(attr);
        }
        self
    }

    /// For structs, include a "builder" type that can be used to construct it.
    pub fn with_struct_builder(&mut self, struct_builder: bool) -> &mut Self {
        self.struct_builder = struct_builder;
        self
    }

    /// Replace a referenced type with a named type. This causes the referenced
    /// type *not* to be generated. If the same `type_name` is specified multiple times,
    /// the last one is honored.
    pub fn with_replacement<TS: ToString, RS: ToString, I: Iterator<Item = TypeSpaceImpl>>(
        &mut self,
        type_name: TS,
        replace_type: RS,
        impls: I,
    ) -> &mut Self {
        self.replace.insert(
            type_name.to_string(),
            TypeSpaceReplace {
                replace_type: replace_type.to_string(),
                impls: impls.collect(),
            },
        );
        self
    }

    /// Modify a type with the given name. Note that specifying a type not
    /// created by the input JSON schema does **not** result in an error and is
    /// silently ignored. If the same `type_name` is specified multiple times,
    /// the last one is honored.
    pub fn with_patch<S: ToString>(
        &mut self,
        type_name: S,
        type_patch: &TypeSpacePatch,
    ) -> &mut Self {
        self.patch.insert(type_name.to_string(), type_patch.clone());
        self
    }

    /// Replace a given schema with a named type. The given schema must precisely
    /// match the schema from the input, including fields such as `description`.
    /// Typical usage is to map a schema definition to a builtin type or type
    /// provided by a crate, such as `'rust_decimal::Decimal'`. If the same schema
    /// is specified multiple times, the first one is honored.
    ///
    /// # Examples
    ///
    /// ```
    /// // Setup 'number' json type to be translated into 'rust_decimal::Decimal'
    /// use schemars::schema::{InstanceType, SchemaObject};
    /// use typify_impl::{TypeSpace, TypeSpaceImpl, TypeSpaceSettings};
    /// let mut type_space = TypeSpace::new(
    ///        TypeSpaceSettings::default()
    ///            .with_struct_builder(true)
    ///            .with_conversion(
    ///                SchemaObject {
    ///                    instance_type: Some(InstanceType::Number.into()),
    ///                    ..Default::default()
    ///                },
    ///                "::rust_decimal::Decimal",
    ///                [TypeSpaceImpl::Display].into_iter(),
    ///            ),
    ///    );
    /// ```
    pub fn with_conversion<S: ToString, I: Iterator<Item = TypeSpaceImpl>>(
        &mut self,
        schema: schemars::schema::SchemaObject,
        type_name: S,
        impls: I,
    ) -> &mut Self {
        self.convert.push(TypeSpaceConversion {
            schema,
            type_name: type_name.to_string(),
            impls: impls.collect(),
        });
        self
    }

    /// Type schemas may contain an extension (`x-rust-type`) that indicates
    /// the corresponding Rust type within a particular crate. This function
    /// changes the disposition regarding crates not otherwise specified via
    /// [`Self::with_crate`]. The default value is `false`.
    pub fn with_unknown_crates(&mut self, policy: UnknownPolicy) -> &mut Self {
        self.unknown_crates = policy;
        self
    }

    /// Type schemas may contain an extension (`x-rust-type`) that indicates
    /// the corresponding Rust type within a particular crate. This extension
    /// indicates the crate, version compatibility, type path, and type
    /// parameters. This function modifies settings to use (rather than
    /// generate) types from the given crate and version. The version should
    /// precisely match the version of the crate that you expect as a
    /// dependency.
    pub fn with_crate<S1: ToString>(
        &mut self,
        crate_name: S1,
        version: CrateVers,
        rename: Option<&String>,
    ) -> &mut Self {
        self.crates.insert(
            crate_name.to_string(),
            CrateSpec {
                version,
                rename: rename.cloned(),
            },
        );
        self
    }

    /// Specify the map-like type to be used in generated code.
    ///
    /// ## Requirements
    ///
    /// - An `is_empty` method that returns a boolean
    /// - Two generic parameters, `K` and `V`
    /// - [`Default`] + [`Clone`] + [`Debug`] +
    ///   [`Serialize`][serde::Serialize] + [`Deserialize`][serde::Deserialize]
    ///
    /// ## Examples
    ///
    /// - [`::std::collections::HashMap`]
    /// - [`::std::collections::BTreeMap`]
    /// - [`::indexmap::IndexMap`](https://docs.rs/indexmap/latest/indexmap/map/struct.IndexMap.html)
    pub fn with_map_type<T: Into<MapType>>(&mut self, map_type: T) -> &mut Self {
        self.map_type = map_type.into();
        self
    }
}

impl TypeSpacePatch {
    /// Specify the new name for patched type.
    pub fn with_rename<S: ToString>(&mut self, rename: S) -> &mut Self {
        self.rename = Some(rename.to_string());
        self
    }

    /// Specify an additional derive to apply to the patched type.
    pub fn with_derive<S: ToString>(&mut self, derive: S) -> &mut Self {
        self.derives.push(derive.to_string());
        self
    }

    /// Specify an additional attribute to apply to the patched type.
    pub fn with_attr<S: ToString>(&mut self, attr: S) -> &mut Self {
        self.attrs.push(attr.to_string());
        self
    }
}

impl TypeSpace {
    /// Create a new TypeSpace with custom settings.
    pub fn new(settings: &TypeSpaceSettings) -> Self {
        let mut cache = SchemaCache::default();

        settings.convert.iter().for_each(
            |TypeSpaceConversion {
                 schema,
                 type_name,
                 impls,
             }| {
                cache.insert(schema, type_name, impls);
            },
        );

        Self {
            settings: settings.clone(),
            cache,
            ..Default::default()
        }
    }

    /// Add a collection of types that will be used as references. Regardless
    /// of how these types are defined--*de novo* or built-in--each type will
    /// appear in the final output as a struct, enum or newtype. This method
    /// may be called multiple times, but collections of references must be
    /// self-contained; in other words, a type in one invocation may not refer
    /// to a type in another invocation.
    // TODO on an error the TypeSpace is in a weird state; we, perhaps, create
    // a child TypeSpace and then merge it in once all conversions hae
    // succeeded.
    pub fn add_ref_types<I, S>(&mut self, type_defs: I) -> Result<()>
    where
        I: IntoIterator<Item = (S, Schema)>,
        S: AsRef<str>,
    {
        self.add_ref_types_impl(
            type_defs
                .into_iter()
                .map(|(key, schema)| (RefKey::Def(key.as_ref().to_string()), schema)),
        )
    }

    fn add_ref_types_impl<I>(&mut self, type_defs: I) -> Result<()>
    where
        I: IntoIterator<Item = (RefKey, Schema)>,
    {
        // Gather up all types to make things a little more convenient.
        let definitions = type_defs.into_iter().collect::<Vec<_>>();

        // Assign IDs to reference types before actually converting them. We'll
        // need these in the case of forward (or circular) references.
        let base_id = self.next_id;
        let def_len = definitions.len() as u64;
        self.next_id += def_len;

        for (index, (ref_name, schema)) in definitions.iter().enumerate() {
            self.ref_to_id
                .insert(ref_name.clone(), TypeId(base_id + index as u64));
            self.definitions.insert(ref_name.clone(), schema.clone());
        }

        // Convert all types; note that we use the type id assigned from the
        // previous step because each type may create additional types. This
        // effectively is doing the work of `add_type_with_name` but for a
        // batch of types.
        for (index, (ref_name, schema)) in definitions.into_iter().enumerate() {
            info!(
                "converting type: {:?} with schema {}",
                ref_name,
                serde_json::to_string(&schema).unwrap()
            );

            // Check for manually replaced types. Proceed with type conversion
            // if there is none; use the specified type if there is.
            let type_id = TypeId(base_id + index as u64);

            let maybe_replace = match &ref_name {
                RefKey::Root => None,
                RefKey::Def(def_name) => {
                    let check_name = sanitize(def_name, Case::Pascal);
                    self.settings.replace.get(&check_name)
                }
            };

            match maybe_replace {
                None => {
                    let type_name = if let RefKey::Def(name) = ref_name {
                        Name::Required(name.clone())
                    } else {
                        Name::Unknown
                    };
                    self.convert_ref_type(type_name, schema, type_id)?
                }

                Some(replace_type) => {
                    let type_entry = TypeEntry::new_native(
                        replace_type.replace_type.clone(),
                        &replace_type.impls.clone(),
                    );
                    self.id_to_entry.insert(type_id, type_entry);
                }
            }
        }

        // Eliminate cycles. It's sufficient to only start from referenced
        // types as a reference is required to make a cycle.
        self.break_cycles(base_id..base_id + def_len);

        // Finalize all created types.
        for index in base_id..self.next_id {
            let type_id = TypeId(index);
            let mut type_entry = self.id_to_entry.get(&type_id).unwrap().clone();
            type_entry.finalize(self)?;
            self.id_to_entry.insert(type_id, type_entry);
        }

        Ok(())
    }

    fn convert_ref_type(&mut self, type_name: Name, schema: Schema, type_id: TypeId) -> Result<()> {
        let (mut type_entry, metadata) = self.convert_schema(type_name.clone(), &schema)?;
        let default = metadata
            .as_ref()
            .and_then(|m| m.default.as_ref())
            .cloned()
            .map(WrappedValue::new);
        let type_entry = match &mut type_entry.details {
            // The types that are already named are good to go.
            TypeEntryDetails::Enum(details) => {
                details.default = default;
                type_entry
            }
            TypeEntryDetails::Struct(details) => {
                details.default = default;
                type_entry
            }
            TypeEntryDetails::Newtype(details) => {
                details.default = default;
                type_entry
            }

            // If the type entry is a reference, then this definition is a
            // simple alias to another type in this list of definitions
            // (which may nor may not have already been converted). We
            // simply create a newtype with that type ID.
            TypeEntryDetails::Reference(type_id) => TypeEntryNewtype::from_metadata(
                self,
                type_name,
                metadata,
                type_id.clone(),
                schema.clone(),
            ),

            TypeEntryDetails::Native(native) if native.name_match(&type_name) => type_entry,

            // For types that don't have names, this is effectively a type
            // alias which we treat as a newtype.
            _ => {
                info!(
                    "type alias {:?} {}\n{:?}",
                    type_name,
                    serde_json::to_string_pretty(&schema).unwrap(),
                    metadata
                );
                let subtype_id = self.assign_type(type_entry);
                TypeEntryNewtype::from_metadata(
                    self,
                    type_name,
                    metadata,
                    subtype_id,
                    schema.clone(),
                )
            }
        };
        // TODO need a type alias?
        if let Some(entry_name) = type_entry.name() {
            self.name_to_id.insert(entry_name.clone(), type_id.clone());
        }
        self.id_to_entry.insert(type_id, type_entry);
        Ok(())
    }

    /// Add a new type and return a type identifier that may be used in
    /// function signatures or embedded within other types.
    pub fn add_type(&mut self, schema: &Schema) -> Result<TypeId> {
        self.add_type_with_name(schema, None)
    }

    /// Add a new type with a name hint and return a the components necessary
    /// to use the type for various components of a function signature.
    pub fn add_type_with_name(
        &mut self,
        schema: &Schema,
        name_hint: Option<String>,
    ) -> Result<TypeId> {
        let base_id = self.next_id;

        let name = match name_hint {
            Some(s) => Name::Suggested(s),
            None => Name::Unknown,
        };
        let (type_id, _) = self.id_for_schema(name, schema)?;

        // Finalize all created types.
        for index in base_id..self.next_id {
            let type_id = TypeId(index);
            let mut type_entry = self.id_to_entry.get(&type_id).unwrap().clone();
            type_entry.finalize(self)?;
            self.id_to_entry.insert(type_id, type_entry);
        }

        Ok(type_id)
    }

    /// Add all the types contained within a RootSchema including any
    /// referenced types and the top-level type (if there is one and it has a
    /// title).
    pub fn add_root_schema(&mut self, schema: RootSchema) -> Result<Option<TypeId>> {
        let RootSchema {
            meta_schema: _,
            schema,
            definitions,
        } = schema;

        let mut defs = definitions
            .into_iter()
            .map(|(key, schema)| (RefKey::Def(key), schema))
            .collect::<Vec<_>>();

        // Does the root type have a name (otherwise... ignore it)
        let root_type = schema
            .metadata
            .as_ref()
            .and_then(|m| m.title.as_ref())
            .is_some();

        if root_type {
            defs.push((RefKey::Root, schema.into()));
        }

        self.add_ref_types_impl(defs)?;

        if root_type {
            Ok(self.ref_to_id.get(&RefKey::Root).cloned())
        } else {
            Ok(None)
        }
    }

    /// Get a type given its ID.
    pub fn get_type(&self, type_id: &TypeId) -> Result<Type<'_>> {
        let type_entry = self.id_to_entry.get(type_id).ok_or(Error::InvalidTypeId)?;
        Ok(Type {
            type_space: self,
            type_entry,
        })
    }

    /// Whether the generated code needs `chrono` crate.
    pub fn uses_chrono(&self) -> bool {
        self.uses_chrono
    }

    /// Whether the generated code needs [regress] crate.
    pub fn uses_regress(&self) -> bool {
        self.uses_regress
    }

    /// Whether the generated code needs [serde_json] crate.
    pub fn uses_serde_json(&self) -> bool {
        self.uses_serde_json
    }

    /// Whether the generated code needs `uuid` crate.
    pub fn uses_uuid(&self) -> bool {
        self.uses_uuid
    }

    /// Iterate over all types including those defined in this [TypeSpace] and
    /// those referred to by those types.
    pub fn iter_types(&self) -> impl Iterator<Item = Type<'_>> {
        self.id_to_entry.values().map(move |type_entry| Type {
            type_space: self,
            type_entry,
        })
    }

    /// All code for processed types.
    pub fn to_stream(&self) -> TokenStream {
        let mut output = OutputSpace::default();

        // Add the error type we use for conversions; it's fine if this is
        // unused.
        output.add_item(
            output::OutputSpaceMod::Error,
            "",
            quote! {
                /// Error from a `TryFrom` or `FromStr` implementation.
                pub struct ConversionError(::std::borrow::Cow<'static, str>);

                impl ::std::error::Error for ConversionError {}
                impl ::std::fmt::Display for ConversionError {
                    fn fmt(&self, f: &mut ::std::fmt::Formatter<'_>)
                        -> Result<(), ::std::fmt::Error>
                    {
                        ::std::fmt::Display::fmt(&self.0, f)
                    }
                }

                impl ::std::fmt::Debug for ConversionError {
                    fn fmt(&self, f: &mut ::std::fmt::Formatter<'_>)
                        -> Result<(), ::std::fmt::Error>
                    {
                        ::std::fmt::Debug::fmt(&self.0, f)
                    }
                }
                impl From<&'static str> for ConversionError {
                    fn from(value: &'static str) -> Self {
                        Self(value.into())
                    }
                }
                impl From<String> for ConversionError {
                    fn from(value: String) -> Self {
                        Self(value.into())
                    }
                }
            },
        );

        // Add all types.
        self.id_to_entry
            .values()
            .for_each(|type_entry| type_entry.output(self, &mut output));

        // Add all shared default functions.
        self.defaults
            .iter()
            .for_each(|x| output.add_item(output::OutputSpaceMod::Defaults, "", x.into()));

        output.into_stream()
    }

    /// Allocated the next TypeId.
    fn assign(&mut self) -> TypeId {
        let id = TypeId(self.next_id);
        self.next_id += 1;
        id
    }

    /// Assign a TypeId for a TypeEntry. This handles resolving references,
    /// checking for duplicate type definitions (e.g. to make sure there aren't
    /// two conflicting types of the same name), and deduplicates various
    /// flavors of built-in types.
    fn assign_type(&mut self, ty: TypeEntry) -> TypeId {
        if let TypeEntryDetails::Reference(type_id) = ty.details {
            type_id
        } else if let Some(name) = ty.name() {
            // If there's already a type of this name, we make sure it's
            // identical. Note that this covers all user-defined types.

            // TODO there are many different choices we might make here
            // that could differ depending on the texture of the schema.
            // For example, a schema might use the string "Response" in a
            // bunch of places and if that were the case we might expect
            // them to be different and resolve that by renaming or scoping
            // them in some way.
            if let Some(type_id) = self.name_to_id.get(name) {
                // TODO we'd like to verify that the type is structurally the
                // same, but the types may not be functionally equal. This is a
                // consequence of types being "finalized" after each type
                // addition. This further emphasized the need for a more
                // deliberate, multi-pass approach.
                type_id.clone()
            } else {
                let type_id = self.assign();
                self.name_to_id.insert(name.clone(), type_id.clone());
                self.id_to_entry.insert(type_id.clone(), ty);
                type_id
            }
        } else if let Some(type_id) = self.type_to_id.get(&ty.details) {
            type_id.clone()
        } else {
            let type_id = self.assign();
            self.type_to_id.insert(ty.details.clone(), type_id.clone());
            self.id_to_entry.insert(type_id.clone(), ty);
            type_id
        }
    }

    /// Convert a schema to a TypeEntry and assign it a TypeId.
    ///
    /// This is used for sub-types such as the type of an array or the types of
    /// properties of a struct.
    fn id_for_schema<'a>(
        &mut self,
        type_name: Name,
        schema: &'a Schema,
    ) -> Result<(TypeId, &'a Option<Box<Metadata>>)> {
        let (mut type_entry, metadata) = self.convert_schema(type_name, schema)?;
        if let Some(metadata) = metadata {
            let default = metadata.default.clone().map(WrappedValue::new);
            match &mut type_entry.details {
                TypeEntryDetails::Enum(details) => {
                    details.default = default;
                }
                TypeEntryDetails::Struct(details) => {
                    details.default = default;
                }
                TypeEntryDetails::Newtype(details) => {
                    details.default = default;
                }
                _ => (),
            }
        }
        let type_id = self.assign_type(type_entry);
        Ok((type_id, metadata))
    }

    /// Create an Option<T> from a pre-assigned TypeId and assign it an ID.
    fn id_to_option(&mut self, id: &TypeId) -> TypeId {
        self.assign_type(TypeEntryDetails::Option(id.clone()).into())
    }

    // Create an Option<T> from a TypeEntry by assigning it type.
    fn type_to_option(&mut self, ty: TypeEntry) -> TypeEntry {
        TypeEntryDetails::Option(self.assign_type(ty)).into()
    }

    /// Create a Box<T> from a pre-assigned TypeId and assign it an ID.
    fn id_to_box(&mut self, id: &TypeId) -> TypeId {
        self.assign_type(TypeEntryDetails::Box(id.clone()).into())
    }
}

impl ToTokens for TypeSpace {
    fn to_tokens(&self, tokens: &mut TokenStream) {
        tokens.extend(self.to_stream())
    }
}

impl Type<'_> {
    /// The name of the type as a String.
    pub fn name(&self) -> String {
        let Type {
            type_space,
            type_entry,
        } = self;
        type_entry.type_name(type_space)
    }

    /// The identifier for the type as might be used for a function return or
    /// defining the type of a member of a struct..
    pub fn ident(&self) -> TokenStream {
        let Type {
            type_space,
            type_entry,
        } = self;
        type_entry.type_ident(type_space, &type_space.settings.type_mod)
    }

    /// The identifier for the type as might be used for a parameter in a
    /// function signature. In general: simple types are the same as
    /// [Type::ident] and complex types prepend a `&`.
    pub fn parameter_ident(&self) -> TokenStream {
        let Type {
            type_space,
            type_entry,
        } = self;
        type_entry.type_parameter_ident(type_space, None)
    }

    /// The identifier for the type as might be used for a parameter in a
    /// function signature along with a lifetime parameter. In general: simple
    /// types are the same as [Type::ident] and complex types prepend a
    /// `&'<lifetime>`.
    pub fn parameter_ident_with_lifetime(&self, lifetime: &str) -> TokenStream {
        let Type {
            type_space,
            type_entry,
        } = self;
        type_entry.type_parameter_ident(type_space, Some(lifetime))
    }

    /// A textual description of the type appropriate for debug output.
    pub fn describe(&self) -> String {
        self.type_entry.describe()
    }

    /// Get details about the type.
    pub fn details(&self) -> TypeDetails<'_> {
        match &self.type_entry.details {
            // Named user-defined types
            TypeEntryDetails::Enum(details) => TypeDetails::Enum(TypeEnum { details }),
            TypeEntryDetails::Struct(details) => TypeDetails::Struct(TypeStruct { details }),
            TypeEntryDetails::Newtype(details) => TypeDetails::Newtype(TypeNewtype { details }),

            // Compound types
            TypeEntryDetails::Option(type_id) => TypeDetails::Option(type_id.clone()),
            TypeEntryDetails::Vec(type_id) => TypeDetails::Vec(type_id.clone()),
            TypeEntryDetails::Map(key_id, value_id) => {
                TypeDetails::Map(key_id.clone(), value_id.clone())
            }
            TypeEntryDetails::Set(type_id) => TypeDetails::Set(type_id.clone()),
            TypeEntryDetails::Box(type_id) => TypeDetails::Box(type_id.clone()),
            TypeEntryDetails::Tuple(types) => TypeDetails::Tuple(Box::new(types.iter().cloned())),
            TypeEntryDetails::Array(type_id, length) => {
                TypeDetails::Array(type_id.clone(), *length)
            }

            // Builtin types
            TypeEntryDetails::Unit => TypeDetails::Unit,
            TypeEntryDetails::Native(TypeEntryNative {
                type_name: name, ..
            })
            | TypeEntryDetails::Integer(name)
            | TypeEntryDetails::Float(name) => TypeDetails::Builtin(name.as_str()),
            TypeEntryDetails::Boolean => TypeDetails::Builtin("bool"),
            TypeEntryDetails::String => TypeDetails::String,
            TypeEntryDetails::JsonValue => TypeDetails::Builtin("::serde_json::Value"),

            // Only used during processing; shouldn't be visible at this point
            TypeEntryDetails::Reference(_) => unreachable!(),
        }
    }

    /// Checks if the type has the associated impl.
    pub fn has_impl(&self, impl_name: TypeSpaceImpl) -> bool {
        let Type {
            type_space,
            type_entry,
        } = self;
        type_entry.has_impl(type_space, impl_name)
    }

    /// Provides the the type identifier for the builder if one exists.
    pub fn builder(&self) -> Option<TokenStream> {
        let Type {
            type_space,
            type_entry,
        } = self;

        if !type_space.settings.struct_builder {
            return None;
        }

        match &type_entry.details {
            TypeEntryDetails::Struct(type_entry::TypeEntryStruct { name, .. }) => {
                match &type_space.settings.type_mod {
                    Some(type_mod) => {
                        let type_mod = format_ident!("{}", type_mod);
                        let type_name = format_ident!("{}", name);
                        Some(quote! { #type_mod :: builder :: #type_name })
                    }
                    None => {
                        let type_name = format_ident!("{}", name);
                        Some(quote! { builder :: #type_name })
                    }
                }
            }
            _ => None,
        }
    }
}

impl<'a> TypeEnum<'a> {
    /// Get name and information of each enum variant.
    pub fn variants(&'a self) -> impl Iterator<Item = (&'a str, TypeEnumVariant<'a>)> {
        self.variants_info().map(|info| (info.name, info.details))
    }

    /// Get all information for each enum variant.
    pub fn variants_info(&'a self) -> impl Iterator<Item = TypeEnumVariantInfo<'a>> {
        self.details.variants.iter().map(move |variant| {
            let details = match &variant.details {
                type_entry::VariantDetails::Simple => TypeEnumVariant::Simple,
                // The distinction between a lone item variant and a tuple
                // variant with a single item is only relevant internally.
                type_entry::VariantDetails::Item(type_id) => {
                    TypeEnumVariant::Tuple(vec![type_id.clone()])
                }
                type_entry::VariantDetails::Tuple(types) => TypeEnumVariant::Tuple(types.clone()),
                type_entry::VariantDetails::Struct(properties) => TypeEnumVariant::Struct(
                    properties
                        .iter()
                        .map(|prop| (prop.name.as_str(), prop.type_id.clone()))
                        .collect(),
                ),
            };
            TypeEnumVariantInfo {
                name: variant.ident_name.as_ref().unwrap(),
                description: variant.description.as_deref(),
                details,
            }
        })
    }
}

impl<'a> TypeStruct<'a> {
    /// Get name and type of each property.
    pub fn properties(&'a self) -> impl Iterator<Item = (&'a str, TypeId)> {
        self.details
            .properties
            .iter()
            .map(move |prop| (prop.name.as_str(), prop.type_id.clone()))
    }

    /// Get all information about each struct property.
    pub fn properties_info(&'a self) -> impl Iterator<Item = TypeStructPropInfo<'a>> {
        self.details
            .properties
            .iter()
            .map(move |prop| TypeStructPropInfo {
                name: prop.name.as_str(),
                description: prop.description.as_deref(),
                required: matches!(&prop.state, StructPropertyState::Required),
                type_id: prop.type_id.clone(),
            })
    }
}

impl TypeNewtype<'_> {
    /// Get the inner type of the newtype struct.
    pub fn inner(&self) -> TypeId {
        self.details.type_id.clone()
    }
}

#[cfg(test)]
mod tests {
    use schema::Schema;
    use schemars::{schema_for, JsonSchema};
    use serde::Serialize;
    use serde_json::json;
    use std::collections::HashSet;

    use crate::{
        output::OutputSpace,
        test_util::validate_output,
        type_entry::{TypeEntryEnum, VariantDetails},
        Name, TypeEntryDetails, TypeSpace, TypeSpaceSettings,
    };

    #[allow(dead_code)]
    #[derive(Serialize, JsonSchema)]
    struct Blah {
        blah: String,
    }

    #[allow(dead_code)]
    #[derive(Serialize, JsonSchema)]
    #[serde(rename_all = "camelCase")]
    //#[serde(untagged)]
    //#[serde(tag = "type", content = "content")]
    enum E {
        /// aaa
        A,
        /// bee
        B,
        /// cee
        //C(Vec<String>),
        C(Blah),
        /// dee
        D {
            /// double D
            dd: String,
        },
        // /// eff
        // F(
        //     /// eff.0
        //     u32,
        //     /// eff.1
        //     u32,
        // ),
    }

    #[allow(dead_code)]
    #[derive(JsonSchema)]
    #[serde(rename_all = "camelCase")]
    struct Foo {
        /// this is bar
        #[serde(default)]
        bar: Option<String>,
        baz_baz: i32,
        /// eeeeee!
        e: E,
    }

    #[test]
    fn test_simple() {
        let schema = schema_for!(Foo);
        println!("{:#?}", schema);
        let mut type_space = TypeSpace::default();
        type_space.add_ref_types(schema.definitions).unwrap();
        let (ty, _) = type_space
            .convert_schema_object(
                Name::Unknown,
                &schemars::schema::Schema::Object(schema.schema.clone()),
                &schema.schema,
            )
            .unwrap();

        println!("{:#?}", ty);

        let mut output = OutputSpace::default();
        ty.output(&type_space, &mut output);
        println!("{}", output.into_stream());

        for ty in type_space.id_to_entry.values() {
            println!("{:#?}", ty);
            let mut output = OutputSpace::default();
            ty.output(&type_space, &mut output);
            println!("{}", output.into_stream());
        }
    }

    #[test]
    fn test_external_references() {
        let schema = json!({
            "$schema": "http://json-schema.org/draft-04/schema#",
            "definitions": {
                "somename": {
                    "$ref": "#/definitions/someothername",
                    "required": [ "someproperty" ]
                },
                "someothername": {
                    "type": "object",
                    "properties": {
                        "someproperty": {
                            "type": "string"
                        }
                    }
                }
            }
        });
        let schema = serde_json::from_value(schema).unwrap();
        println!("{:#?}", schema);
        let settings = TypeSpaceSettings::default();
        let mut type_space = TypeSpace::new(&settings);
        type_space.add_root_schema(schema).unwrap();
        let tokens = type_space.to_stream().to_string();
        println!("{}", tokens);
        assert!(tokens
            .contains(" pub struct Somename { pub someproperty : :: std :: string :: String , }"))
    }

    #[test]
    fn test_convert_enum_string() {
        #[allow(dead_code)]
        #[derive(JsonSchema)]
        #[serde(rename_all = "camelCase")]
        enum SimpleEnum {
            DotCom,
            Grizz,
            Kenneth,
        }

        let schema = schema_for!(SimpleEnum);
        println!("{:#?}", schema);

        let mut type_space = TypeSpace::default();
        type_space.add_ref_types(schema.definitions).unwrap();
        let (ty, _) = type_space
            .convert_schema_object(
                Name::Unknown,
                &schemars::schema::Schema::Object(schema.schema.clone()),
                &schema.schema,
            )
            .unwrap();

        match ty.details {
            TypeEntryDetails::Enum(TypeEntryEnum { variants, .. }) => {
                for variant in &variants {
                    assert_eq!(variant.details, VariantDetails::Simple);
                }
                let var_names = variants
                    .iter()
                    .map(|variant| variant.ident_name.as_ref().unwrap().clone())
                    .collect::<HashSet<_>>();
                assert_eq!(
                    var_names,
                    ["DotCom", "Grizz", "Kenneth",]
                        .iter()
                        .map(ToString::to_string)
                        .collect::<HashSet<_>>()
                );
            }
            _ => {
                let mut output = OutputSpace::default();
                ty.output(&type_space, &mut output);
                println!("{}", output.into_stream());
                panic!();
            }
        }
    }

    #[test]
    fn test_string_enum_with_null() {
        let original_schema = json!({ "$ref": "xxx"});
        let enum_values = vec![
            json!("Shadrach"),
            json!("Meshach"),
            json!("Abednego"),
            json!(null),
        ];

        let mut type_space = TypeSpace::default();
        let (te, _) = type_space
            .convert_enum_string(
                Name::Required("OnTheGo".to_string()),
                &serde_json::from_value(original_schema).unwrap(),
                &None,
                &enum_values,
                None,
            )
            .unwrap();

        if let TypeEntryDetails::Option(id) = &te.details {
            let ote = type_space.id_to_entry.get(id).unwrap();
            if let TypeEntryDetails::Enum(TypeEntryEnum { variants, .. }) = &ote.details {
                let variants = variants
                    .iter()
                    .map(|v| match v.details {
                        VariantDetails::Simple => v.ident_name.as_ref().unwrap().clone(),
                        _ => panic!("unexpected variant type"),
                    })
                    .collect::<HashSet<_>>();

                assert_eq!(
                    variants,
                    enum_values
                        .iter()
                        .flat_map(|j| j.as_str().map(ToString::to_string))
                        .collect::<HashSet<_>>()
                );
            } else {
                panic!("not the sub-type we expected {:#?}", te)
            }
        } else {
            panic!("not the type we expected {:#?}", te)
        }
    }

    #[test]
    fn test_alias() {
        #[allow(dead_code)]
        #[derive(JsonSchema, Schema)]
        struct Stuff(Vec<String>);

        #[allow(dead_code)]
        #[derive(JsonSchema, Schema)]
        struct Things {
            a: String,
            b: Stuff,
        }

        validate_output::<Things>();
    }

    #[test]
    fn test_builder_name() {
        #[allow(dead_code)]
        #[derive(JsonSchema)]
        struct TestStruct {
            x: u32,
        }

        let mut type_space = TypeSpace::default();
        let schema = schema_for!(TestStruct);
        let type_id = type_space.add_root_schema(schema).unwrap().unwrap();
        let ty = type_space.get_type(&type_id).unwrap();

        assert!(ty.builder().is_none());

        let mut type_space = TypeSpace::new(TypeSpaceSettings::default().with_struct_builder(true));
        let schema = schema_for!(TestStruct);
        let type_id = type_space.add_root_schema(schema).unwrap().unwrap();
        let ty = type_space.get_type(&type_id).unwrap();

        assert_eq!(
            ty.builder().map(|ts| ts.to_string()),
            Some("builder :: TestStruct".to_string())
        );

        let mut type_space = TypeSpace::new(
            TypeSpaceSettings::default()
                .with_type_mod("types")
                .with_struct_builder(true),
        );
        let schema = schema_for!(TestStruct);
        let type_id = type_space.add_root_schema(schema).unwrap().unwrap();
        let ty = type_space.get_type(&type_id).unwrap();

        assert_eq!(
            ty.builder().map(|ts| ts.to_string()),
            Some("types :: builder :: TestStruct".to_string())
        );

        #[allow(dead_code)]
        #[derive(JsonSchema)]
        enum TestEnum {
            X,
            Y,
        }
        let mut type_space = TypeSpace::new(
            TypeSpaceSettings::default()
                .with_type_mod("types")
                .with_struct_builder(true),
        );
        let schema = schema_for!(TestEnum);
        let type_id = type_space.add_root_schema(schema).unwrap().unwrap();
        let ty = type_space.get_type(&type_id).unwrap();
        assert!(ty.builder().is_none());
    }
}