From 35f4f561535ab7542da07003566b56d5a0895e65 Mon Sep 17 00:00:00 2001
From: Alec Gibson <12036746+alecgibson@users.noreply.github.com>
Date: Thu, 17 Oct 2024 17:04:14 +0100
Subject: [PATCH] =?UTF-8?q?=F0=9F=90=9B=20Fix=20`closed`=20check=20when=20?=
 =?UTF-8?q?handling=20`querySubscribe()`?=
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The `Agent` attempts to check if it's been closed when getting the
response for a query subscribe.

However, it incorrectly tries to access `this` inside a `function`,
which doesn't give the correct value, and in `strict mode`, will
actually result in an error, since `this` will be `undefined`.

This change adds a test for this case and fixes it.
---
 lib/agent.js                   |  2 +-
 test/client/query-subscribe.js | 23 +++++++++++++++++++++++
 2 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/lib/agent.js b/lib/agent.js
index 1352d6600..a07650c8a 100644
--- a/lib/agent.js
+++ b/lib/agent.js
@@ -569,7 +569,7 @@ Agent.prototype._querySubscribe = function(queryId, collection, query, options,
   }
   this.backend.querySubscribe(this, collection, query, options, function(err, emitter, results, extra) {
     if (err) return finish(err);
-    if (this.closed) return emitter.destroy();
+    if (agent.closed) return emitter.destroy();
 
     agent._subscribeToQuery(emitter, queryId, collection, query);
     // No results are returned when ids are passed in as an option. Instead,
diff --git a/test/client/query-subscribe.js b/test/client/query-subscribe.js
index 95e286f9a..4cf690ff9 100644
--- a/test/client/query-subscribe.js
+++ b/test/client/query-subscribe.js
@@ -729,6 +729,29 @@ function commonTests(options) {
     connection.get('dogs', 'fido').on('error', done).create({age: 3});
   });
 
+  it('does not reply if the agent is closed before the query returns', function(done) {
+    var backend = this.backend;
+    var connection = backend.connect();
+    var agent = connection.agent;
+
+    backend.use('query', function(request, next) {
+      backend.use('reply', function() {
+        done(new Error('unexpected reply'));
+      });
+
+      expect(agent.closed).to.be.false;
+      agent.stream.on('close', function() {
+        expect(agent.closed).to.be.true;
+        next();
+        done();
+      });
+
+      agent.close();
+    });
+
+    connection.createSubscribeQuery('dogs', {});
+  });
+
   describe('passing agent.custom to the DB adapter', function() {
     var connection;
     var expectedArg = {