Allow specifying scalar and context for GraphQLEnum (#621)

* Updated implementation of derive enum

- allows context specification
- allows scalar specification
- shares code with derive object

* Added this feature to CHANGELOG

* Added matrix with supported macro attributes for enums

* Added case which checks for custom context

* GraphQLUnion now can use a different context per variant

* Moved context switch test for union into right folder

* Sync resolve expression has the same form as the other impls

* Disabled custom scalar on GraphQLEnum

* Fixed CHANGELOG

* Fixed support matrix of GraphQLEnum in the book

- scalar not supported!
- skip not supported!

* Added test case for "noasync" derive attribute

* Disallowed generics and lifetimes on GraphQLEnum

* Added error message for duplicate naming

* Added error message for empty variant

Author: jmpunkt

docs/book/content/types/enums.md

@@ -54,3 +54,17 @@ enum StarWarsEpisode {
 
 # fn main() {}
 ```
+
+## Supported Macro Attributes (Derive)
+
+| Name of Attribute | Container Support | Field Support    |
+|-------------------|:-----------------:|:----------------:|
+| context           | ✔                 | ?                |
+| deprecated        | ✔                 | ✔                |
+| description       | ✔                 | ✔                |
+| interfaces        | ?                 | ✘                |
+| name              | ✔                 | ✔                |
+| noasync           | ✔                 | ?                |
+| scalar            | ✘                 | ?                |
+| skip              | ?                 | ✘                |
+| ✔: supported      | ✘: not supported  | ?: not available |

integration_tests/juniper_tests/src/codegen/derive_enum.rs

@@ -4,6 +4,10 @@ use fnv::FnvHashMap;
 #[cfg(test)]
 use juniper::{self, DefaultScalarValue, FromInputValue, GraphQLType, InputValue, ToInputValue};
 
+pub struct CustomContext {}
+
+impl juniper::Context for CustomContext {}
+
 #[derive(juniper::GraphQLEnum, Debug, PartialEq)]
 #[graphql(name = "Some", description = "enum descr")]
 enum SomeEnum {
@@ -39,6 +43,12 @@ enum OverrideDocEnum {
     Foo,
 }
 
+#[derive(juniper::GraphQLEnum)]
+#[graphql(context = CustomContext, noasync)]
+enum ContextEnum {
+    A,
+}
+
 #[test]
 fn test_derived_enum() {
     // Ensure that rename works.
@@ -98,3 +108,16 @@ fn test_doc_comment_override() {
     let meta = OverrideDocEnum::meta(&(), &mut registry);
     assert_eq!(meta.description(), Some(&"enum override".to_string()));
 }
+
+fn test_context<T>(_t: T)
+where
+    T: GraphQLType<DefaultScalarValue, Context = CustomContext>,
+{
+    // empty
+}
+
+#[test]
+fn test_doc_custom_context() {
+    test_context(ContextEnum::A);
+    // test_context(OverrideDocEnum::Foo); does not work
+}

integration_tests/juniper_tests/src/codegen/derive_union.rs

@@ -91,6 +91,13 @@ impl DroidCompat {
     }
 }
 
+#[derive(juniper::GraphQLUnion)]
+#[graphql(Context = CustomContext)]
+pub enum DifferentContext {
+    A(DroidContext),
+    B(Droid),
+}
+
 // NOTICE: this can not compile due to generic implementation of GraphQLType<__S>
 // #[derive(juniper::GraphQLUnion)]
 // pub enum CharacterCompatFail {

juniper/CHANGELOG.md

@@ -27,6 +27,8 @@ See [#569](https://github.com/graphql-rust/juniper/pull/569).
 
 See [#618](https://github.com/graphql-rust/juniper/pull/618).
 
+- Derive macro `GraphQLEnum` supports custom context (see [#621](https://github.com/graphql-rust/juniper/pull/621))
+
 ## Breaking Changes
 
 - `juniper::graphiql` has moved to `juniper::http::graphiql`