add subscribe/resolve wrappers

src/builders/buildFieldConfigMap.ts

@@ -1,7 +1,7 @@
 import { AnyConstructor, EmptyConstructor, isEmptyConstructor, Maybe, ObjectLiteral } from '../types';
 import { resolveThunk, Thunk } from '../utils/thunk';
 import { GraphQLFieldConfigMap, GraphQLFieldResolver } from 'graphql';
-import { FieldConfig, FieldConfigMap, FieldResolver } from '../fields';
+import { FieldConfig, FieldConfigMap, FieldResolver, FieldSubscriber, SubscriptionFieldConfigMap } from '../fields';
 import {
   getArgsConfig,
   getFieldConfig,
@@ -34,6 +34,13 @@ type InputConstructorNode<T> = {
   children: InputConstructorChildren,
 }
 
+const isInSubscribe = Symbol();
+
+type WrappedSubscribePayload<T> = {
+  [isInSubscribe]: true,
+  value: T,
+}
+
 const buildInputConstructorTree = <T>(InputClass: EmptyConstructor<T>): Maybe<InputConstructorNode<T>> => {
   const map = isArgs(InputClass) ? getArgsConfig(InputClass) : getInputFieldConfig(InputClass);
   if (!map) {
@@ -105,6 +112,48 @@ export const buildFieldConfigMap = <TSource, TContext>(
   }));
 };
 
+const wrapSubscribe = <TSource, TContext, TReturn, TArgs>(
+  subscribe: FieldSubscriber<TSource, TContext, TReturn, TArgs>,
+): FieldSubscriber<TSource, TContext, WrappedSubscribePayload<TReturn>, TArgs> => {
+  return async function * (...args) {
+    const iterator = subscribe(...args);
+    for await (const value of iterator) {
+      yield {
+        [isInSubscribe]: true,
+        value,
+      }
+    }
+  }
+}
+
+function wrapSubscriptionResolve<TSource, TContext, TReturn, TArgs>(
+  resolve?: FieldResolver<TSource, TContext, TReturn, TArgs>,
+): FieldResolver<WrappedSubscribePayload<TSource>, TContext, TReturn | TSource, TArgs> {
+  return (root, ...args) => {
+    if (!root[isInSubscribe]) {
+      throw new Error('Subscription field resolve called without subscribe');
+    }
+
+    if (!resolve) {
+      return root.value;
+    }
+
+    return resolve(root.value, ...args);
+  }
+}
+
+export const buildSubscriptionFieldConfigMap = <TSource, TContext>(
+  map: SubscriptionFieldConfigMap<TSource, TContext>,
+): GraphQLFieldConfigMap<any, TContext> => {
+  return mapValues(map, (config) => ({
+    ...config,
+    resolve: wrapSubscriptionResolve(config.resolve),
+    subscribe: wrapSubscribe(config.subscribe),
+    type: buildOutputType(config.type, true),
+    args: config.args ? resolveThunk(getArgs(config.args)) : undefined,
+  }));
+}
+
 const defaultResolver = (key: string) => (source: ObjectLiteral, ...rest: any[]) => {
   const resolve = convertResolverMethod(source, key);
   if (resolve) {

src/fields.ts

@@ -3,7 +3,7 @@ import { MaybePromise, EmptyConstructor, MaybeArray, AnyConstructor } from './ty
 import { GraphQLOutputType, GraphQLResolveInfo, subscribe } from 'graphql';
 import { mergeThunks, resolveThunk, Thunk } from './utils/thunk';
 import { isArray } from 'lodash';
-import { buildFieldConfigMap } from './builders/buildFieldConfigMap';
+import { buildFieldConfigMap, buildSubscriptionFieldConfigMap } from './builders/buildFieldConfigMap';
 import Field from './decorators/Field';
 
 export type FieldCreatorConfig<TReturn, TArgs = {}> = {
@@ -18,7 +18,7 @@ export type FieldResolver<TSource, TContext, TReturn, TArgs = {}> =
   (source: TSource, args: TArgs, context: TContext, info: GraphQLResolveInfo) => MaybePromise<TReturn>;
 
 export type FieldSubscriber<TSource, TContext, TReturn, TArgs = {}> =
-  (source: TSource, args: TArgs, context: TContext, info: GraphQLResolveInfo) => AsyncIterator<TReturn>;
+  (source: TSource, args: TArgs, context: TContext, info: GraphQLResolveInfo) => AsyncIterable<TReturn>;
 
 export type FieldConfig<TSource, TContext, TReturn, TArgs = {}> = FieldCreatorConfig<TReturn, TArgs> & {
   resolve?: FieldResolver<TSource, TContext, TReturn, TArgs>,
@@ -30,7 +30,7 @@ type SubscriptionFieldConfigSimple<
   TReturn,
   TArgs = {},
 > = FieldConfig<TSource, TContext, TReturn, TArgs> & {
-  subscribe?: FieldSubscriber<TSource, TContext, TReturn, TArgs>,
+  subscribe: FieldSubscriber<TSource, TContext, TReturn, TArgs>,
 };
 
 type SubscriptionFieldConfigWithResolver<
@@ -41,7 +41,7 @@ type SubscriptionFieldConfigWithResolver<
   TArgs = {},
 > = FieldConfig<TSource, TContext, TReturn, TArgs> & {
   resolve?: FieldResolver<TSubReturn, TContext, TReturn, TArgs>,
-  subscribe?: FieldSubscriber<TSource, TContext, TSubReturn, TArgs>,
+  subscribe: FieldSubscriber<TSource, TContext, TSubReturn, TArgs>,
 };
 
 export type SubscriptionFieldConfig<TSource, TContext, TReturn, TSubReturn, TArgs = {}> =
@@ -124,13 +124,13 @@ export const subscriptionFields = <TSource = undefined, TContext = undefined>(
 };
 
 export const buildFields = <TSource, TContext>(fields: MaybeArray<Thunk<FieldConfigMap<TSource, TContext>>>) => {
-  let thunk = isArray(fields) ? mergeThunks(...fields) : fields;
+  const thunk = isArray(fields) ? mergeThunks(...fields) : fields;
   const configMap = resolveThunk(thunk);
   return buildFieldConfigMap(configMap);
 }
 
 export const buildSubscriptionFields = <TSource, TContext>(fields: MaybeArray<Thunk<SubscriptionFieldConfigMap<TSource, TContext>>>) => {
-  let thunk = isArray(fields) ? mergeThunks(...fields) : fields;
+  const thunk = isArray(fields) ? mergeThunks(...fields) : fields;
   const configMap = resolveThunk(thunk);
-  // TODO
+  return buildSubscriptionFieldConfigMap(configMap);
 };

src/index.ts

@@ -15,7 +15,7 @@ import buildInputObjectType from './builders/buildInputObjectType';
 import buildInterfaceType from './builders/buildInterfaceType';
 import buildObjectType from './builders/buildObjectType';
 import { buildInputType, buildNamedType, buildNamedTypes, buildOutputType, buildType } from './typeHelpers';
-import { buildFields, fields } from './fields';
+import { buildFields, buildSubscriptionFields, fields, subscriptionFields } from './fields';
 import { TSGraphQLBoolean, TSGraphQLFloat, TSGraphQLID, TSGraphQLInt, TSGraphQLString } from './wrappers/scalars';
 import scalarType from './wrappers/scalarType';
 
@@ -51,5 +51,7 @@ export {
   buildType,
   fields,
   buildFields,
+  subscriptionFields,
+  buildSubscriptionFields,
   fieldDecoratorForContext,
 };