Derive Macro GraphQLObject

#[derive(GraphQLObject)]
{
    // Attributes available to this derive:
    #[graphql]
}

#[derive(GraphQLObject)] macro for deriving a GraphQL object implementation for structs.

The #[graphql] helper attribute is used for configuring the derived implementation. Specifying multiple #[graphql] attributes on the same definition is totally okay. They all will be treated as a single attribute.

use juniper::GraphQLObject;

#[derive(GraphQLObject)]
struct Query {
    // NOTICE: By default, field names will be converted to `camelCase`.
    //         In the generated GraphQL schema this field will be available
    //         as `apiVersion`.
    api_version: &'static str,
}

Custom name, description and deprecation

The name of GraphQL object or its field may be overridden with a name attribute’s argument. By default, a type name is used or camelCased field name.

The description of GraphQL object or its field may be specified either with a description/desc attribute’s argument, or with a regular Rust doc comment.

A field of GraphQL object may be deprecated by specifying a deprecated attribute’s argument, or with regular Rust #[deprecated] attribute.

#[derive(GraphQLObject)]
#[graphql(
    // Rename the type for GraphQL by specifying the name here.
    name = "Human",
    // You may also specify a description here.
    // If present, doc comments will be ignored.
    desc = "Possible episode human.",
)]
struct HumanWithAttrs {
    #[graphql(name = "id", desc = "ID of the human.")]
    #[graphql(deprecated = "Don't use it")]
    some_id: String,
}

// Rust docs are used as GraphQL description.
/// Possible episode human.
#[derive(GraphQLObject)]
struct HumanWithDocs {
    // Doc comments also work on fields.
    /// ID of the human.
    #[deprecated]
    id: String,
}

Renaming policy

By default, all GraphQL object fields are renamed via camelCase policy (so api_version: String becomes apiVersion field in GraphQL schema, and so on). This complies with default GraphQL naming conventions [demonstrated in spec][0].

However, if you need for some reason apply another naming convention, it’s possible to do by using rename_all attribute’s argument. At the moment it supports the following policies only: SCREAMING_SNAKE_CASE, camelCase, none (disables any renaming).

#[derive(GraphQLObject)]
#[graphql(rename_all = "none")] // disables renaming
struct Query {
    // NOTICE: In the generated GraphQL schema this field will be available
    //         as `api_version`.
    api_version: String,
}

Ignoring struct fields

To omit exposing a struct field in the GraphQL schema, use an ignore attribute’s argument directly on that field.

#[derive(GraphQLObject)]
struct Human {
    id: String,
    #[graphql(ignore)]
    home_planet: String,
    #[graphql(skip)]
    //        ^^^^ alternative naming, up to your preference
    password_hash: String,
}

Custom ScalarValue

By default, #[derive(GraphQLObject)] macro generates code, which is generic over a ScalarValue type. This may introduce a problem when at least one of its fields is restricted to a concrete ScalarValue type in its implementation. To resolve such problem, a concrete ScalarValue type should be specified with a scalar attribute’s argument.

#[derive(GraphQLObject)]
// NOTICE: Removing `scalar` argument will fail compilation.
#[graphql(scalar = DefaultScalarValue)]
struct Human {
    id: String,
    helper: Droid,
}

#[derive(GraphQLObject)]
#[graphql(scalar = DefaultScalarValue)]
struct Droid {
    id: String,
}