(WIP) Subscriptions support

For now this is mostly about cleaning up how we handle the operations from the query. This paves the way for validating that we only have one field in a subscription (as per the spec) and for selecting an operation for a multi-operation document later.

Author: tomhoule

graphql_query_derive/src/constants.rs

@@ -22,3 +22,9 @@ pub fn typename_field() -> GqlObjectField {
         type_: FieldType::Named(string_type()),
     }
 }
+
+pub const MULTIPLE_SUBSCRIPTION_FIELDS_ERROR: &str = r##"
+Multiple-field queries on the root subscription field are forbidden by the spec.
+
+See: https://github.com/facebook/graphql/blob/master/spec/Section%205%20--%20Validation.md#subscription-operation-definitions
+"##;

graphql_query_derive/src/lib.rs

@@ -24,6 +24,7 @@ mod inputs;
 mod interfaces;
 mod introspection_response;
 mod objects;
+mod operations;
 mod query;
 mod scalars;
 mod schema;

graphql_query_derive/src/operations.rs

@@ -0,0 +1,21 @@
+use selection::Selection;
+
+pub enum OperationType {
+    Query,
+    Mutation,
+    Subscription,
+}
+
+#[derive(Debug)]
+pub struct Operation {
+    pub name: String,
+    pub selection: Selection,
+}
+
+pub struct Operations(Vec<Operation>);
+
+impl Operations {
+    fn from_document(doc: ::graphql_parser::query::Document) -> Result<Self, ::failure::Error> {
+        unimplemented!()
+    }
+}

graphql_query_derive/src/query.rs

@@ -9,10 +9,8 @@ use variables::Variable;
 
 /// This holds all the information we need during the code generation phase.
 pub struct QueryContext {
-    pub _subscription_root: Option<Vec<TokenStream>>,
+    pub root: Option<Vec<TokenStream>>,
     pub fragments: BTreeMap<String, GqlFragment>,
-    pub mutation_root: Option<Vec<TokenStream>>,
-    pub query_root: Option<Vec<TokenStream>>,
     pub schema: Schema,
     pub variables: Vec<Variable>,
 }
@@ -21,10 +19,8 @@ impl QueryContext {
     /// Create a QueryContext with the given Schema.
     pub fn new(schema: Schema) -> QueryContext {
         QueryContext {
-            _subscription_root: None,
+            root: None,
             fragments: BTreeMap::new(),
-            mutation_root: None,
-            query_root: None,
             schema,
             variables: Vec::new(),
         }
@@ -72,10 +68,8 @@ impl QueryContext {
     #[cfg(test)]
     pub fn new_empty() -> QueryContext {
         QueryContext {
-            _subscription_root: None,
             fragments: BTreeMap::new(),
-            mutation_root: None,
-            query_root: None,
+            root: None,
             schema: Schema::new(),
             variables: Vec::new(),
         }

graphql_query_derive/src/schema.rs

@@ -78,7 +78,7 @@ impl Schema {
         for definition in query.definitions {
             match definition {
                 query::Definition::Operation(query::OperationDefinition::Query(q)) => {
-                    context.query_root = {
+                    context.root = {
                         let definition = context
                             .schema
                             .query_type
@@ -101,7 +101,7 @@ impl Schema {
                     context.register_variables(&q.variable_definitions);
                 }
                 query::Definition::Operation(query::OperationDefinition::Mutation(q)) => {
-                    context.mutation_root = {
+                    context.root = {
                         let definition = context
                             .schema
                             .mutation_type
@@ -124,7 +124,7 @@ impl Schema {
                     context.register_variables(&q.variable_definitions);
                 }
                 query::Definition::Operation(query::OperationDefinition::Subscription(q)) => {
-                    context._subscription_root = {
+                    context.root = {
                         let definition = context
                             .schema
                             .subscription_type
@@ -173,12 +173,7 @@ impl Schema {
             .collect();
         let fragment_definitions = fragment_definitions?;
         let variables_struct = context.expand_variables();
-        let response_data_fields = context
-            .query_root
-            .as_ref()
-            .or_else(|| context.mutation_root.as_ref())
-            .or_else(|| context._subscription_root.as_ref())
-            .expect("no selection defined");
+        let response_data_fields = context.root.as_ref().expect("no selection defined");
 
         let input_object_definitions: Result<Vec<TokenStream>, _> = context
             .schema