Macro juniper::graphql_enum

macro_rules! graphql_enum {
    ( @as_expr, $e:expr) => { ... };
    ( @as_pattern, $p:pat) => { ... };
    ( @as_path, $p:path) => { ... };
    ( @maybe_apply, None, $func:ident, $val:expr ) => { ... };
    ( @maybe_apply, $arg:tt, $func:ident, $val:expr ) => { ... };
    (
        @generate,
        ( $name:path, $outname:tt, $descr:tt ),
        [ $( ( $eval:tt, $ename:tt, $edescr:tt, $edepr:tt ) , )* ]
    ) => { ... };
    ( @parse, $meta:tt, $acc:tt, ) => { ... };
    ( @parse, $meta:tt, $acc:tt, , $($rest:tt)* ) => { ... };
    (
        @parse,
        ( $name:tt, $outname:tt, $_ignore:tt ),
        $acc:tt,
        description: $descr:tt $($items:tt)*
    ) => { ... };
    (
        @parse,
        $meta:tt,
        [ $($acc:tt ,)* ],
        $eval:path => $ename:tt deprecated $depr:tt $($rest:tt)*
    ) => { ... };
    (
        @parse,
        $meta:tt,
        [ $($acc:tt ,)* ],
        $eval:path => $ename:tt as $descr:tt deprecated $depr:tt $($rest:tt)*
    ) => { ... };
    (
        @parse,
        $meta:tt,
        [ $($acc:tt ,)* ],
        $eval:path => $ename:tt as $descr:tt $($rest:tt)*
    ) => { ... };
    (
        @parse,
        $meta:tt,
        [ $($acc:tt ,)* ],
        $eval:path => $ename:tt $($rest:tt)*
    ) => { ... };
    (
        $name:path as $outname:tt { $($items:tt)* }
    ) => { ... };
    (
        $name:path { $($items:tt)* }
    ) => { ... };
}

Expose simple enums

GraphQL enums are similar to enums classes C++ - more like grouped constants with type safety than what Rust enums offer. This macro can be used to export non-data carrying Rust enums to GraphQL:

enum Color {
    Red,
    Orange,
    Green,
    Blue,
    Black,
}

graphql_enum!(Color {
    Color::Red => "RED" as "The color red",
    Color::Orange => "ORANGE",
    Color::Green => "GREEN",
    Color::Blue => "BLUE",
    Color::Black => "BLACK" deprecated "Superseded by ORANGE",
});

The macro expands to a match statement which will result in a compilation error if not all enum variants are covered. It also creates an implementation for FromInputValue and ToInputValue, making it usable in arguments and default values.

If you want to expose the enum under a different name than the Rust type, you can write graphql_enum!(Color as "MyColor" { ....