From 06bc375cca85aeb298327b0363d36352b73b0865 Mon Sep 17 00:00:00 2001
From: Tyler Neely <t@jujit.su>
Date: Wed, 19 May 2021 14:48:39 +0200
Subject: [PATCH 1/2] Idempotent UNSUB avoids sending multiple UNSUB messages
 when subscriptions are dropped or manually unsubscribed.

---
 CHANGELOG.md          |  7 +++++++
 Cargo.toml            |  2 +-
 async-nats/Cargo.toml |  4 ++--
 src/client.rs         | 10 +++++++++-
 4 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 54c837910..70ca6761c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,13 @@
 
 ## Improvements
 
+- #180 idempotent unsubscription avoids sending
+  multiple UNSUB messages.
+
+# 0.9.16
+
+## Improvements
+
 - #178 client state has been reorganized to allow
   reading and writing to make progress independently,
   preventing issues that were sometimes encountered
diff --git a/Cargo.toml b/Cargo.toml
index 8ecc17b21..a384d1d07 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "nats"
-version = "0.9.16"
+version = "0.9.17"
 description = "A Rust NATS client"
 authors = ["Derek Collison <derek@nats.io>", "Tyler Neely <tyler@nats.io>", "Stjepan Glavina <stjepan@nats.io>"]
 edition = "2018"
diff --git a/async-nats/Cargo.toml b/async-nats/Cargo.toml
index aa68d9542..bf71aeafa 100644
--- a/async-nats/Cargo.toml
+++ b/async-nats/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "async-nats"
-version = "0.9.16"
+version = "0.9.17"
 description = "An async Rust NATS client"
 authors = ["Derek Collison <derek@nats.io>", "Tyler Neely <tyler@nats.io>", "Stjepan Glavina <stjepan@nats.io>"]
 edition = "2018"
@@ -17,7 +17,7 @@ maintenance = { status = "actively-developed" }
 
 [dependencies]
 blocking = "1.0.2"
-nats = { path = "..", version = "0.9.16" }
+nats = { path = "..", version = "0.9.17" }
 
 [dev-dependencies]
 smol = "1.2.5"
diff --git a/src/client.rs b/src/client.rs
index 533ae7575..a692ed346 100644
--- a/src/client.rs
+++ b/src/client.rs
@@ -348,7 +348,15 @@ impl Client {
         let mut read = self.state.read.lock();
 
         // Remove the subscription from the map.
-        read.subscriptions.remove(&sid);
+        if read.subscriptions.remove(&sid).is_none() {
+            // already unsubscribed
+
+            // NB see locking protocol for state.write and state.read
+            drop(read);
+            drop(write);
+
+            return Ok(());
+        }
 
         // Send an UNSUB message.
         if let Some(writer) = write.writer.as_mut() {

From a4596177b94533a821f065ce21a2633aee62a4c8 Mon Sep 17 00:00:00 2001
From: Tyler Neely <t@jujit.su>
Date: Wed, 19 May 2021 14:49:24 +0200
Subject: [PATCH 2/2] Fix CHANGELOG

---
 CHANGELOG.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 70ca6761c..173c65f27 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,4 +1,4 @@
-# 0.9.16
+# 0.9.17
 
 ## Improvements