oapi: Add support for inlined enum variants (#859)

* oapi: Add support for inlined enum variants

* Format Rust code using rustfmt

* fix ci

---------

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

crates/oapi-macros/src/schema/struct_schemas.rs

@@ -8,8 +8,8 @@ use syn::{punctuated::Punctuated, spanned::Spanned, Attribute, Field, Generics,
 use crate::component::{ComponentDescription, ComponentSchemaProps};
 use crate::doc_comment::CommentAttributes;
 use crate::feature::{
-    pop_feature, pop_feature_as_inner, Alias, Bound, Feature, FeaturesExt, IsSkipped, Name, RenameAll, SkipBound,
-    TryToTokensExt,
+    parse_features, pop_feature, pop_feature_as_inner, Alias, Bound, Feature, FeaturesExt, IsSkipped, Name, RenameAll,
+    SkipBound, TryToTokensExt,
 };
 use crate::schema::{Description, Inline};
 use crate::type_tree::TypeTree;
@@ -18,7 +18,7 @@ use crate::{
 };
 
 use super::{
-    feature::{FromAttributes, NamedFieldFeatures},
+    feature::{parse_schema_features_with, FromAttributes, NamedFieldFeatures},
     is_flatten, is_not_skipped, ComponentSchema, FieldRename, FlattenedMapSchema, Property,
 };
 
@@ -354,6 +354,13 @@ impl TryToTokens for UnnamedStructSchema<'_> {
 
             if fields_len == 1 {
                 if let Some(ref mut features) = unnamed_struct_features {
+                    let inline = parse_schema_features_with(&first_field.attrs, |input| {
+                        Ok(parse_features!(input as crate::feature::Inline))
+                    })?
+                    .unwrap_or_default();
+
+                    features.extend(inline);
+
                     if pop_feature!(features => Feature::Default(crate::feature::Default(None))).is_some() {
                         let struct_ident = format_ident!("{}", &self.struct_name);
                         let index: syn::Index = 0.into();

crates/oapi/docs/derive_to_schema.md

@@ -73,6 +73,30 @@ In addition to the variant type specific configuration options enum variants sup
 _`rename`_ attribute. It behaves similarly to serde's _`rename`_ attribute. If both _serde_
 _`rename`_ and _schema_ _`rename`_ are defined __serde__ will take precedence.
 
+## Enum Unnamed Variant Field Configuration Options
+
+* `inline` If the type of this field implements [`ToSchema`][to_schema], then the schema definition
+will be inlined. **warning:** Don't use this for recursive data types!
+
+_**Inline unnamed field variant schemas.**_
+```
+use salvo_oapi::ToSchema;
+#[derive(ToSchema)]
+enum Number {
+    One,
+}
+
+#[derive(ToSchema)]
+enum Color {
+    Spade,
+}
+#[derive(ToSchema)]
+enum Card {
+    Number(#[salvo(schema(inline))] Number),
+    Color(#[salvo(schema(inline))] Color),
+}
+```
+
 # Unnamed Field Struct Optional Configuration Options for `#[salvo(schema(...))]`
 
 * `description = ...` Can be literal string or Rust expression e.g. _`const`_ reference or