From d1a319c5f280c8b4f30ce9f6d31ce227ef78586f Mon Sep 17 00:00:00 2001
From: Graham Esau <gesau@hotmail.co.uk>
Date: Sun, 4 Aug 2019 19:49:41 +0100
Subject: [PATCH] Generate schemas for simple enums

---
 schemars/src/main.rs       |  4 ++--
 schemars_derive/src/lib.rs | 22 +++++++++++++++++++++-
 2 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/schemars/src/main.rs b/schemars/src/main.rs
index e77c95f..533a945 100644
--- a/schemars/src/main.rs
+++ b/schemars/src/main.rs
@@ -2,7 +2,7 @@ use schemars::MakeSchema;
 use serde::{Deserialize, Serialize};
 use serde_json::Result;
 
-#[derive(Serialize, Deserialize, Debug)]
+#[derive(Serialize, Deserialize, Debug, MakeSchema)]
 #[serde(rename_all = "camelCase")]
 enum TodoStatus {
     Backlog,
@@ -17,7 +17,7 @@ struct Todo {
     id: u64,
     title: String,
     description: Option<String>,
-    // status: TodoStatus,
+    status: TodoStatus,
     assigned_to: Vec<User>,
 }
 
diff --git a/schemars_derive/src/lib.rs b/schemars_derive/src/lib.rs
index bf83f82..18408c9 100644
--- a/schemars_derive/src/lib.rs
+++ b/schemars_derive/src/lib.rs
@@ -25,7 +25,8 @@ pub fn derive_make_schema(input: proc_macro::TokenStream) -> proc_macro::TokenSt
 
     let fn_contents = match cont.data {
         Data::Struct(Style::Struct, ref fields) => struct_implementation(fields),
-        _ => unimplemented!("Only structs work so far!"),
+        Data::Enum(ref variants) => enum_implementation(variants),
+        _ => unimplemented!("work in progress!"),
     };
 
     let impl_block = quote! {
@@ -49,6 +50,25 @@ fn compile_error(span: Span, message: String) -> TokenStream {
     }
 }
 
+fn is_unit_variant(v: &Variant) -> bool {
+    match v.style {
+        Style::Unit => true,
+        _ => false,
+    }
+}
+
+fn enum_implementation(variants: &[Variant]) -> TokenStream {
+    if variants.iter().all(is_unit_variant) {
+        let names = variants
+            .into_iter()
+            .map(|v| v.attrs.name().deserialize_name());
+        return quote! {
+            o.enum_values = Some(vec![#(#names.into()),*]);
+        };
+    }
+    unimplemented!("work in progress!")
+}
+
 fn struct_implementation(fields: &[Field]) -> TokenStream {
     let recurse = fields.into_iter().map(|f| {
         let name = f.attrs.name().deserialize_name();