Add support for GraphQL Schema Language

Fixes #307.

README.md

@@ -46,8 +46,7 @@ see the [hyper][hyper_examples], [rocket][rocket_examples], [iron][iron_examples
 
 Juniper supports the full GraphQL query language according to the
 [specification][graphql_spec], including interfaces, unions, schema
-introspection, and validations.
-It does not, however, support the schema language.
+introspection, and validations. It can also output the schema in the [GraphQL Schema Language][schema_language].
 
 As an exception to other GraphQL libraries for other languages, Juniper builds
 non-null types by default. A field of type `Vec<Episode>` will be converted into
@@ -86,6 +85,7 @@ Juniper has not reached 1.0 yet, thus some API instability should be expected.
 [playground]: https://github.com/prisma/graphql-playground
 [iron]: http://ironframework.io
 [graphql_spec]: http://facebook.github.io/graphql
+[schema_language]: https://graphql.org/learn/schema/#type-language
 [test_schema_rs]: https://github.com/graphql-rust/juniper/blob/master/juniper/src/tests/schema.rs
 [tokio]: https://github.com/tokio-rs/tokio
 [hyper_examples]: https://github.com/graphql-rust/juniper/tree/master/juniper_hyper/examples

juniper/CHANGELOG.md

@@ -6,6 +6,26 @@
   The DirectiveLocation::InlineFragment had an invalid literal value,
   which broke third party tools like apollo cli.
 - Added GraphQL Playground integration
+- Added the `schema-language` feature (on by default). This feature enables converting
+  the schema to a `String` in the
+  [GraphQL Schema Language](https://graphql.org/learn/schema/#type-language)
+  format (usually written to a file called `schema.graphql`).
+
+  Example:
+
+  ```rust
+    use juniper::{RootNode, EmptyMutation};
+
+    #[derive(GraphQLObject)]
+    struct Query{
+      foo: bool
+    };
+    let s = RootNode::new(Query, EmptyMutation::<()>::new());
+    println!("{}, s.as_schema_language());
+  ```
+
+  Note: The `schema-language` feature brings in more dependencies.
+  If you don't use the schema language you may want to turn the feature off.
 
 # [0.11.1] 2018-12-19
 

juniper/Cargo.toml

@@ -24,10 +24,13 @@ path = "benches/bench.rs"
 [features]
 nightly = []
 expose-test-schema = []
+schema-language = ["graphql-parser-integration"]
+graphql-parser-integration = ["graphql-parser"]
 default = [
     "chrono",
     "url",
     "uuid",
+    "schema-language",
 ]
 
 [dependencies]
@@ -42,6 +45,7 @@ chrono = { version = "0.4.0", optional = true }
 serde_json = { version="1.0.2", optional = true }
 url = { version = "1.5.1", optional = true }
 uuid = { version = "0.7", optional = true }
+graphql-parser = {version = "0.2.2", optional = true }
 
 [dev-dependencies]
 bencher = "0.1.2"

juniper/src/lib.rs

@@ -103,13 +103,16 @@ extern crate fnv;
 
 extern crate indexmap;
 
-#[cfg(any(test, feature = "chrono"))]
+#[cfg(feature = "graphql-parser-integration")]
+extern crate graphql_parser;
+
+#[cfg(feature = "chrono")]
 extern crate chrono;
 
-#[cfg(any(test, feature = "url"))]
+#[cfg(feature = "url")]
 extern crate url;
 
-#[cfg(any(test, feature = "uuid"))]
+#[cfg(feature = "uuid")]
 extern crate uuid;
 
 // Depend on juniper_codegen and re-export everything in it.

juniper/src/schema/meta.rs

@@ -165,6 +165,14 @@ pub struct Field<'a, S> {
     pub deprecation_status: DeprecationStatus,
 }
 
+impl<'a, S> Field<'a, S> {
+    /// Returns true if the type is built-in to GraphQL.
+    pub fn is_builtin(&self) -> bool {
+        // "used exclusively by GraphQL’s introspection system"
+        self.name.starts_with("__")
+    }
+}
+
 /// Metadata for an argument to a field
 #[derive(Debug, Clone)]
 pub struct Argument<'a, S> {
@@ -178,6 +186,14 @@ pub struct Argument<'a, S> {
     pub default_value: Option<InputValue<S>>,
 }
 
+impl<'a, S> Argument<'a, S> {
+    /// Returns true if the type is built-in to GraphQL.
+    pub fn is_builtin(&self) -> bool {
+        // "used exclusively by GraphQL’s introspection system"
+        self.name.starts_with("__")
+    }
+}
+
 /// Metadata for a single value in an enum
 #[derive(Debug, Clone)]
 pub struct EnumValue {
@@ -364,6 +380,22 @@ impl<'a, S> MetaType<'a, S> {
         }
     }
 
+    /// Returns true if the type is built-in to GraphQL.
+    pub fn is_builtin(&self) -> bool {
+        if let Some(name) = self.name() {
+            // "used exclusively by GraphQL’s introspection system"
+            {
+                name.starts_with("__") ||
+            // <https://facebook.github.io/graphql/draft/#sec-Scalars>
+            name == "Boolean" || name == "String" || name == "Int" || name == "Float" || name == "ID" ||
+            // Our custom empty mutation marker
+            name == "_EmptyMutation"
+            }
+        } else {
+            false
+        }
+    }
+
     pub(crate) fn fields<'b>(&self, schema: &'b SchemaType<S>) -> Option<Vec<&'b Field<'b, S>>> {
         schema
             .lookup_type(&self.as_type())

juniper/src/schema/mod.rs

@@ -1,3 +1,4 @@
 pub mod meta;
 pub mod model;
 pub mod schema;
+pub mod translate;

juniper/src/schema/model.rs

@@ -4,7 +4,14 @@ use fnv::FnvHashMap;
 
 use ast::Type;
 use executor::{Context, Registry};
+#[cfg(feature = "graphql-parser-integration")]
+use graphql_parser::schema::Document;
 use schema::meta::{Argument, InterfaceMeta, MetaType, ObjectMeta, PlaceholderMeta, UnionMeta};
+#[cfg(feature = "graphql-parser-integration")]
+use schema::translate::graphql_parser::GraphQLParserAst;
+#[cfg(feature = "graphql-parser-integration")]
+use schema::translate::AstTranslator;
+
 use types::base::GraphQLType;
 use types::name::Name;
 use value::{DefaultScalarValue, ScalarRefValue, ScalarValue};
@@ -35,8 +42,8 @@ where
 #[derive(Debug)]
 pub struct SchemaType<'a, S> {
     pub(crate) types: FnvHashMap<Name, MetaType<'a, S>>,
-    query_type_name: String,
-    mutation_type_name: Option<String>,
+    pub(crate) query_type_name: String,
+    pub(crate) mutation_type_name: Option<String>,
     directives: FnvHashMap<String, DirectiveType<'a, S>>,
 }
 
@@ -88,6 +95,22 @@ where
     {
         RootNode::new_with_info(query_obj, mutation_obj, (), ())
     }
+
+    #[cfg(feature = "schema-language")]
+    /// The schema definition as a `String` in the
+    /// [GraphQL Schema Language](https://graphql.org/learn/schema/#type-language)
+    /// format.
+    pub fn as_schema_language(&self) -> String {
+        let doc = self.as_parser_document();
+        format!("{}", doc)
+    }
+
+    #[cfg(feature = "graphql-parser-integration")]
+    /// The schema definition as a [`graphql_parser`](https://crates.io/crates/graphql-parser)
+    /// [`Document`](https://docs.rs/graphql-parser/latest/graphql_parser/schema/struct.Document.html).
+    pub fn as_parser_document(&self) -> Document {
+        GraphQLParserAst::translate_schema(&self.schema)
+    }
 }
 
 impl<'a, S, QueryT, MutationT> RootNode<'a, QueryT, MutationT, S>
@@ -466,3 +489,92 @@ impl<'a, S> fmt::Display for TypeType<'a, S> {
         }
     }
 }
+
+#[cfg(test)]
+mod test {
+
+    #[cfg(feature = "graphql-parser-integration")]
+    mod graphql_parser_integration {
+        use EmptyMutation;
+
+        #[test]
+        fn graphql_parser_doc() {
+            struct Query;
+            graphql_object!(Query: () |&self| {
+                field blah() -> bool {
+                    true
+                }
+            });
+            let schema = crate::RootNode::new(Query, EmptyMutation::<()>::new());
+            let ast = graphql_parser::parse_schema(
+                r#"
+                type Query {
+                  blah: Boolean!
+                }
+
+                schema {
+                  query: Query
+                }
+            "#,
+            )
+            .unwrap();
+            assert_eq!(
+                format!("{}", ast),
+                format!("{}", schema.as_parser_document()),
+            );
+        }
+    }
+
+    #[cfg(feature = "schema-language")]
+    mod schema_language {
+        use EmptyMutation;
+
+        #[test]
+        fn schema_language() {
+            struct Query;
+            graphql_object!(Query: () |&self| {
+                field blah() -> bool {
+                    true
+                }
+                /// This is whatever's description.
+                field whatever() -> String {
+                    "foo".to_string()
+                }
+                field fizz(buzz: String) -> Option<&str> {
+                    None
+                }
+                field arr(stuff: Vec<String>) -> Option<&str> {
+                    None
+                }
+                #[deprecated]
+                field old() -> i32 {
+                    42
+                }
+                #[deprecated(note="This field is deprecated, use another.")]
+                field really_old() -> f64 {
+                    42.0
+                }
+            });
+            let schema = crate::RootNode::new(Query, EmptyMutation::<()>::new());
+            let ast = graphql_parser::parse_schema(
+                r#"
+                type Query {
+                  blah: Boolean!
+                  "This is whatever's description."
+                  whatever: String!
+                  fizz(buzz: String!): String
+                  arr(stuff: [String!]!): String
+                  old: Int! @deprecated
+                  reallyOld: Float! @deprecated(reason: "This field is deprecated, use another.")
+                }
+
+                schema {
+                  query: Query
+                }
+            "#,
+            )
+            .unwrap();
+            assert_eq!(format!("{}", ast), schema.as_schema_language());
+        }
+    }
+}