use darling::ast::{Data, Style};
use proc_macro::TokenStream;
use proc_macro2::{Ident, Span};
use quote::quote;
use std::collections::HashSet;
use syn::visit_mut::VisitMut;
use syn::{visit_mut, Error, Lifetime, Type};
use crate::args::{self, RenameTarget};
use crate::utils::{get_crate_name, get_rustdoc, visible_fn, GeneratorResult};
pub fn generate(union_args: &args::Union) -> GeneratorResult<TokenStream> {
let crate_name = get_crate_name(union_args.internal);
let ident = &union_args.ident;
let (impl_generics, ty_generics, where_clause) = union_args.generics.split_for_impl();
let s = match &union_args.data {
Data::Enum(s) => s,
_ => {
return Err(Error::new_spanned(&ident, "Union can only be applied to an enum.").into())
}
};
let mut enum_names = Vec::new();
let mut enum_items = HashSet::new();
let mut type_into_impls = Vec::new();
let gql_typename = union_args
.name
.clone()
.unwrap_or_else(|| RenameTarget::Type.rename(ident.to_string()));
let desc = get_rustdoc(&union_args.attrs)?
.map(|s| quote! { ::std::option::Option::Some(#s) })
.unwrap_or_else(|| quote! {::std::option::Option::None});
let mut registry_types = Vec::new();
let mut possible_types = Vec::new();
let mut get_introspection_typename = Vec::new();
let mut collect_all_fields = Vec::new();
for variant in s {
let enum_name = &variant.ident;
let ty = match variant.fields.style {
Style::Tuple if variant.fields.fields.len() == 1 => &variant.fields.fields[0],
Style::Tuple => {
return Err(Error::new_spanned(
enum_name,
"Only single value variants are supported",
)
.into())
}
Style::Unit => {
return Err(
Error::new_spanned(enum_name, "Empty variants are not supported").into(),
)
}
Style::Struct => {
return Err(Error::new_spanned(
enum_name,
"Variants with named fields are not supported",
)
.into())
}
};
if let Type::Path(p) = &ty {
if !enum_items.insert(p) {
return Err(
Error::new_spanned(&ty, "This type already used in another variant").into(),
);
}
enum_names.push(enum_name);
struct RemoveLifetime;
impl VisitMut for RemoveLifetime {
fn visit_lifetime_mut(&mut self, i: &mut Lifetime) {
i.ident = Ident::new("_", Span::call_site());
visit_mut::visit_lifetime_mut(self, i);
}
}
let mut assert_ty = p.clone();
RemoveLifetime.visit_type_path_mut(&mut assert_ty);
if !variant.flatten {
type_into_impls.push(quote! {
#crate_name::static_assertions::assert_impl_one!(#assert_ty: #crate_name::ObjectType);
#[allow(clippy::all, clippy::pedantic)]
impl #impl_generics ::std::convert::From<#p> for #ident #ty_generics #where_clause {
fn from(obj: #p) -> Self {
#ident::#enum_name(obj)
}
}
});
} else {
type_into_impls.push(quote! {
#crate_name::static_assertions::assert_impl_one!(#assert_ty: #crate_name::UnionType);
#[allow(clippy::all, clippy::pedantic)]
impl #impl_generics ::std::convert::From<#p> for #ident #ty_generics #where_clause {
fn from(obj: #p) -> Self {
#ident::#enum_name(obj)
}
}
});
}
if !variant.flatten {
registry_types.push(quote! {
<#p as #crate_name::Type>::create_type_info(registry);
});
possible_types.push(quote! {
possible_types.insert(<#p as #crate_name::Type>::type_name().into_owned());
});
} else {
possible_types.push(quote! {
if let #crate_name::registry::MetaType::Union { possible_types: possible_types2, .. } =
registry.create_dummy_type::<#p>() {
possible_types.extend(possible_types2);
}
});
}
if !variant.flatten {
get_introspection_typename.push(quote! {
#ident::#enum_name(obj) => <#p as #crate_name::Type>::type_name()
});
} else {
get_introspection_typename.push(quote! {
#ident::#enum_name(obj) => <#p as #crate_name::Type>::introspection_type_name(obj)
});
}
collect_all_fields.push(quote! {
#ident::#enum_name(obj) => obj.collect_all_fields(ctx, fields)
});
} else {
return Err(Error::new_spanned(ty, "Invalid type").into());
}
}
if possible_types.is_empty() {
return Err(Error::new_spanned(
&ident,
"A GraphQL Union type must include one or more unique member types.",
)
.into());
}
let visible = visible_fn(&union_args.visible);
let expanded = quote! {
#(#type_into_impls)*
#[allow(clippy::all, clippy::pedantic)]
impl #impl_generics #crate_name::Type for #ident #ty_generics #where_clause {
fn type_name() -> ::std::borrow::Cow<'static, ::std::primitive::str> {
::std::borrow::Cow::Borrowed(#gql_typename)
}
fn introspection_type_name(&self) -> ::std::borrow::Cow<'static, ::std::primitive::str> {
match self {
#(#get_introspection_typename),*
}
}
fn create_type_info(registry: &mut #crate_name::registry::Registry) -> ::std::string::String {
registry.create_type::<Self, _>(|registry| {
#(#registry_types)*
#crate_name::registry::MetaType::Union {
name: ::std::borrow::ToOwned::to_owned(#gql_typename),
description: #desc,
possible_types: {
let mut possible_types = #crate_name::indexmap::IndexSet::new();
#(#possible_types)*
possible_types
},
visible: #visible,
}
})
}
}
#[allow(clippy::all, clippy::pedantic)]
#[#crate_name::async_trait::async_trait]
impl #impl_generics #crate_name::resolver_utils::ContainerType for #ident #ty_generics #where_clause {
async fn resolve_field(&self, ctx: &#crate_name::Context<'_>) -> #crate_name::ServerResult<::std::option::Option<#crate_name::Value>> {
::std::result::Result::Ok(::std::option::Option::None)
}
fn collect_all_fields<'__life>(&'__life self, ctx: &#crate_name::ContextSelectionSet<'__life>, fields: &mut #crate_name::resolver_utils::Fields<'__life>) -> #crate_name::ServerResult<()> {
match self {
#(#collect_all_fields),*
}
}
}
#[allow(clippy::all, clippy::pedantic)]
#[#crate_name::async_trait::async_trait]
impl #impl_generics #crate_name::OutputType for #ident #ty_generics #where_clause {
async fn resolve(&self, ctx: &#crate_name::ContextSelectionSet<'_>, _field: &#crate_name::Positioned<#crate_name::parser::types::Field>) -> #crate_name::ServerResult<#crate_name::Value> {
#crate_name::resolver_utils::resolve_container(ctx, self).await
}
}
impl #impl_generics #crate_name::UnionType for #ident #ty_generics #where_clause {}
};
Ok(expanded.into())
}