From b197408bc80efdf5ab8c8dffbdab0d70e2c8f191 Mon Sep 17 00:00:00 2001
From: Denis Badurina <badurinadenis@gmail.com>
Date: Fri, 24 Jan 2020 17:59:35 +0100
Subject: [PATCH] feat(subscriptions): @pgSubscription now supports filter
 (#596)

---
 .../src/PgSubscriptionResolverPlugin.ts        | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/packages/pg-pubsub/src/PgSubscriptionResolverPlugin.ts b/packages/pg-pubsub/src/PgSubscriptionResolverPlugin.ts
index 378a74d93..699d65b59 100644
--- a/packages/pg-pubsub/src/PgSubscriptionResolverPlugin.ts
+++ b/packages/pg-pubsub/src/PgSubscriptionResolverPlugin.ts
@@ -1,6 +1,6 @@
 import debugFactory from "debug";
 import { Plugin } from "graphile-build";
-import { PubSub } from "graphql-subscriptions";
+import { PubSub, withFilter } from "graphql-subscriptions";
 
 const debug = debugFactory("pg-pubsub");
 
@@ -38,13 +38,14 @@ const PgSubscriptionResolverPlugin: Plugin = function(builder, { pubsub }) {
       const {
         topic: topicGen,
         unsubscribeTopic: unsubscribeTopicGen,
+        filter,
       } = pgSubscription;
       if (!topicGen) {
         return field;
       }
       return extend(field, {
         subscribe: async (
-          _parent: any,
+          parent: any,
           args: any,
           resolveContext: any,
           resolveInfo: any
@@ -94,6 +95,19 @@ const PgSubscriptionResolverPlugin: Plugin = function(builder, { pubsub }) {
             });
           }
 
+          if (filter) {
+            if (typeof filter !== "function") {
+              throw new Error(
+                "filter provided to pgSubscription must be a function"
+              );
+            }
+            return withFilter(() => asyncIterator, filter)(
+              parent,
+              args,
+              resolveContext,
+              resolveInfo
+            );
+          }
           return asyncIterator;
         },
         ...(field.resolve