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juniper-from-schema

Build crates.io Documentation

This library contains a procedural macro that reads a GraphQL schema file, and generates the corresponding Juniper macro calls. This means you can have a real schema file and be guaranteed that it matches your Rust implementation. It also removes most of the boilerplate involved in using Juniper.

Looking for juniper 0.15 support?

The version of juniper-from-schema that is released on crates.io (0.5.2) doesn't support juniper 0.15. However the master branch does! So you will have to use a git dependency for now. We plan to do an official release soon. Follow this milestone to see whats left.

Example

Imagine you have a GraphQL schema like this:

schema {
  query: Query
}

type Query {
  helloWorld(name: String!): String! @juniper(ownership: "owned")
}

That can be implemented like so:

use juniper_from_schema::graphql_schema_from_file;

// This is the important line
graphql_schema_from_file!("readme_schema.graphql");

pub struct Context;

impl juniper::Context for Context {}

pub struct Query;

// This trait is generated by `graphql_schema_from_file!` based on the schema
impl QueryFields for Query {
    fn field_hello_world(
        &self,
        _executor: &juniper::Executor<Context>,
        name: String,
    ) -> juniper::FieldResult<String> {
        Ok(format!("Hello, {}!", name))
    }
}

fn main() {
    let ctx = Context;

    let query = "query { helloWorld(name: \"Ferris\") }";

    let (result, errors) = juniper::execute_sync(
        query,
        None,
        &Schema::new(Query, juniper::EmptyMutation::new()),
        &juniper::Variables::new(),
        &ctx,
    )
    .unwrap();

    assert_eq!(errors.len(), 0);
    assert_eq!(
        result
            .as_object_value()
            .unwrap()
            .get_field_value("helloWorld")
            .unwrap()
            .as_scalar_value::<String>()
            .unwrap(),
        "Hello, Ferris!",
    );
}

See the crate documentation for a usage examples and more info.

N+1s

If you're having issues with N+1 query bugs consider using juniper-eager-loading. It was built to integrate seamlessly with juniper-from-schema.

Development

If you're seeing No such file or directory (os error 2) when running the tests

This might be caused by setting CARGO_TARGET_DIR. Setting that env var changes the directory the trybuild tests are run from which means all the paths to the test schemas no longer match. The only workaround is to unset CARGO_TARGET_DIR when working on juniper-from-schema. I recommend direnv to unset the env var only this directory and not globally.

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Schema first GraphQL in Rust with Juniper

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