openapi: when Union uses discriminator, if the members is not an `O…

…bject`, an error will be reported at compile time. #755

Cargo.toml

@@ -46,6 +46,8 @@ base64 = "0.21.0"
 serde_urlencoded = "0.7.1"
 indexmap = "2.0.0"
 reqwest = { version = "0.11.23", default-features = false }
+darling = "0.20.8"
+static_assertions = "1.1.0"
 
 # rustls, update together
 rustls = "0.22.0"

poem-openapi-derive/Cargo.toml

@@ -16,7 +16,7 @@ categories = ["network-programming", "asynchronous"]
 proc-macro = true
 
 [dependencies]
-darling = "0.20.1"
+darling.workspace = true
 proc-macro-crate.workspace = true
 proc-macro2.workspace = true
 quote.workspace = true

poem-openapi-derive/src/object.rs

@@ -412,6 +412,8 @@ pub(crate) fn generate(args: DeriveInput) -> GeneratorResult<TokenStream> {
  }
  }
 
+ impl #impl_generics #crate_name::types::IsObjectType for #ident #ty_generics #where_clause {}
+
  impl #impl_generics #crate_name::types::ParseFromJSON for #ident #ty_generics #where_clause {
  fn parse_from_json(value: ::std::option::Option<#crate_name::__private::serde_json::Value>) -> ::std::result::Result<Self, #crate_name::types::ParseError<Self>> {
  let value = value.unwrap_or_default();

poem-openapi-derive/src/union.rs

@@ -145,6 +145,7 @@ pub(crate) fn generate(args: DeriveInput) -> GeneratorResult<TokenStream> {
 
  if let Some(discriminator_name) = &args.discriminator_name {
  create_schemas.push(quote! {
+ #crate_name::__private::static_assertions::assert_impl_all!(#object_ty: #crate_name::types::IsObjectType);
  let schema = #crate_name::registry::MetaSchema {
  all_of: ::std::vec![
  #crate_name::registry::MetaSchemaRef::Inline(::std::boxed::Box::new(#crate_name::registry::MetaSchema {
@@ -268,6 +269,7 @@ pub(crate) fn generate(args: DeriveInput) -> GeneratorResult<TokenStream> {
  }
 
  fn register(registry: &mut #crate_name::registry::Registry) {
+ use ::std::marker::Sized;
  registry.create_schema::<Self, _>(<Self as #crate_name::types::Type>::name().into_owned(), |registry| {
  #(<#types as #crate_name::types::Type>::register(registry);)*
  #(#create_schemas)*

poem-openapi/Cargo.toml

@@ -50,6 +50,7 @@ thiserror.workspace = true
 bytes.workspace = true
 futures-util.workspace = true
 indexmap.workspace = true
+static_assertions.workspace = true
 
 # Non-feature optional dependencies
 email_address = { version = "0.2.1", optional = true }

poem-openapi/src/lib.rs

@@ -189,6 +189,7 @@ pub mod __private {
  pub use poem;
  pub use serde;
  pub use serde_json;
+ pub use static_assertions;
 
  pub use crate::{auth::CheckerReturn, base::UrlQuery, path_util::join_path};
 }

poem-openapi/src/types/mod.rs

@@ -82,6 +82,9 @@ pub trait Type: Send + Sync {
  }
 }
 
+/// Represents a object type.
+pub trait IsObjectType: Type {}
+
 /// Represents a type that can parsing from JSON.
 pub trait ParseFromJSON: Sized + Type {
  /// Parse from [`serde_json::Value`].

poem-openapi/tests/security_scheme.rs

@@ -3,7 +3,7 @@ use poem::{
  http::{header, StatusCode},
  test::TestClient,
  web::{cookie::Cookie, headers},
- Error, Request,
+ Request,
 };
 use poem_openapi::{
  auth::{ApiKey, Basic, Bearer},