From a725594cd1e8f5fc2ebbf15f112092d65fd0f5ab Mon Sep 17 00:00:00 2001
From: Sunli <scott_s829@163.com>
Date: Sun, 27 Sep 2020 16:05:25 +0800
Subject: [PATCH] Add `remote` attribute for Enum macro. #276

---
 derive/src/args.rs | 12 +++++++++++
 derive/src/enum.rs | 54 ++++++++++++++++++++++++++++++++++++++++------
 tests/enum.rs      | 22 +++++++++++++++++++
 3 files changed, 81 insertions(+), 7 deletions(-)

diff --git a/derive/src/args.rs b/derive/src/args.rs
index e16694fb..62507a14 100644
--- a/derive/src/args.rs
+++ b/derive/src/args.rs
@@ -326,6 +326,7 @@ pub struct Enum {
     pub internal: bool,
     pub name: Option<String>,
     pub desc: Option<String>,
+    pub remote: Option<String>,
 }
 
 impl Enum {
@@ -333,6 +334,7 @@ impl Enum {
         let mut internal = false;
         let mut name = None;
         let mut desc = None;
+        let mut remote = None;
 
         for arg in args {
             match arg {
@@ -358,6 +360,15 @@ impl Enum {
                                 "Attribute 'desc' should be a string.",
                             ));
                         }
+                    } else if nv.path.is_ident("remote") {
+                        if let syn::Lit::Str(lit) = nv.lit {
+                            remote = Some(lit.value());
+                        } else {
+                            return Err(Error::new_spanned(
+                                &nv.lit,
+                                "Attribute 'remote' should be a string.",
+                            ));
+                        }
                     }
                 }
                 _ => {}
@@ -368,6 +379,7 @@ impl Enum {
             internal,
             name,
             desc,
+            remote,
         })
     }
 }
diff --git a/derive/src/enum.rs b/derive/src/enum.rs
index f2d350c3..0fab3b0f 100644
--- a/derive/src/enum.rs
+++ b/derive/src/enum.rs
@@ -1,5 +1,5 @@
 use crate::args;
-use crate::utils::{get_crate_name, get_rustdoc};
+use crate::utils::{get_cfg_attrs, get_crate_name, get_rustdoc};
 use inflector::Inflector;
 use proc_macro::TokenStream;
 use quote::quote;
@@ -39,11 +39,6 @@ pub fn generate(enum_args: &args::Enum, input: &DeriveInput) -> Result<TokenStre
         }
 
         let item_ident = &variant.ident;
-        let item_attrs = variant
-            .attrs
-            .iter()
-            .filter(|attr| !attr.path.is_ident("item"))
-            .collect::<Vec<_>>();
         let mut item_args = args::EnumItem::parse(&variant.attrs)?;
         let gql_item_name = item_args
             .name
@@ -59,7 +54,7 @@ pub fn generate(enum_args: &args::Enum, input: &DeriveInput) -> Result<TokenStre
             .as_ref()
             .map(|s| quote! { Some(#s) })
             .unwrap_or_else(|| quote! {None});
-        enum_items.push(quote! { #(#item_attrs)* #item_ident});
+        enum_items.push((get_cfg_attrs(&variant.attrs), item_ident));
         items.push(quote! {
             #crate_name::resolver_utils::EnumItem {
                 name: #gql_item_name,
@@ -75,6 +70,49 @@ pub fn generate(enum_args: &args::Enum, input: &DeriveInput) -> Result<TokenStre
         });
     }
 
+    let remote_conversion = if let Some(remote) = &enum_args.remote {
+        let remote_ty = if let Ok(ty) = syn::parse_str::<syn::Type>(remote) {
+            ty
+        } else {
+            return Err(Error::new_spanned(
+                remote,
+                format!("Invalid remote type: '{}'", remote),
+            ));
+        };
+
+        let local_to_remote_items = enum_items.iter().map(|(cfg_attrs, item)| {
+            quote! {
+                #(#cfg_attrs)*
+                #ident::#item => #remote_ty::#item,
+            }
+        });
+        let remote_to_local_items = enum_items.iter().map(|(cfg_attrs, item)| {
+            quote! {
+                #(#cfg_attrs)*
+                #remote_ty::#item => #ident::#item,
+            }
+        });
+        Some(quote! {
+            impl ::std::convert::From<#ident> for #remote_ty {
+                fn from(value: #ident) -> Self {
+                    match value {
+                        #(#local_to_remote_items)*
+                    }
+                }
+            }
+
+            impl ::std::convert::From<#remote_ty> for #ident {
+                fn from(value: #remote_ty) -> Self {
+                    match value {
+                        #(#remote_to_local_items)*
+                    }
+                }
+            }
+        })
+    } else {
+        None
+    };
+
     let expanded = quote! {
         #[allow(clippy::all, clippy::pedantic)]
         impl #crate_name::resolver_utils::EnumType for #ident {
@@ -122,6 +160,8 @@ pub fn generate(enum_args: &args::Enum, input: &DeriveInput) -> Result<TokenStre
             }
         }
 
+        #remote_conversion
+
         impl #crate_name::type_mark::TypeMarkEnum for #ident {}
     };
     Ok(expanded.into())
diff --git a/tests/enum.rs b/tests/enum.rs
index b6521e46..e45b7472 100644
--- a/tests/enum.rs
+++ b/tests/enum.rs
@@ -70,3 +70,25 @@ pub async fn test_enum_derive_and_item_attributes() {
         TestStruct { value: Test::Real }
     );
 }
+
+#[async_std::test]
+pub async fn test_remote_enum() {
+    #[derive(Enum, Copy, Clone, Eq, PartialEq)]
+    #[graphql(remote = "remote::RemoteEnum")]
+    enum LocalEnum {
+        A,
+        B,
+        C,
+    }
+
+    mod remote {
+        pub enum RemoteEnum {
+            A,
+            B,
+            C,
+        }
+    }
+
+    let _: remote::RemoteEnum = LocalEnum::A.into();
+    let _: LocalEnum = remote::RemoteEnum::A.into();
+}