[MM-870]: Fixed issue of deletion of non-existent subscription

server/plugin/command.go

@@ -599,6 +599,10 @@ func (p *Plugin) handleUnsubscribe(_ *plugin.Context, args *model.CommandArgs, p
 	owner = strings.ToLower(owner)
 	repo = strings.ToLower(repo)
 	if err := p.Unsubscribe(args.ChannelId, repo, owner); err != nil {
+		if strings.Contains(err.Error(), "no subscription exists") {
+			return err.Error()
+		}
+
 		p.client.Log.Warn("Failed to unsubscribe", "repo", repo, "error", err.Error())
 		return "Encountered an error trying to unsubscribe. Please try again."
 	}

server/plugin/subscriptions.go

@@ -17,11 +17,12 @@ import (
 )
 
 const (
-	SubscriptionsKey      = "subscriptions"
-	flagExcludeOrgMember  = "exclude-org-member"
-	flagRenderStyle       = "render-style"
-	flagFeatures          = "features"
-	flagExcludeRepository = "exclude"
+	SubscriptionsKey        = "subscriptions"
+	flagExcludeOrgMember    = "exclude-org-member"
+	flagRenderStyle         = "render-style"
+	flagFeatures            = "features"
+	flagExcludeRepository   = "exclude"
+	SubscriptionUnavailable = "no subscription exists for `%s` in the channel"
 )
 
 type SubscriptionFlags struct {
@@ -388,7 +389,7 @@ func (p *Plugin) Unsubscribe(channelID, repo, owner string) error {
 
 	repoSubs := subs.Repositories[repoWithOwner]
 	if repoSubs == nil {
-		return nil
+		return errors.Errorf(SubscriptionUnavailable, strings.TrimSuffix(repoWithOwner, "/"))
 	}
 
 	removed := false
@@ -405,6 +406,8 @@ func (p *Plugin) Unsubscribe(channelID, repo, owner string) error {
 		if err := p.StoreSubscriptions(subs); err != nil {
 			return errors.Wrap(err, "could not store subscriptions")
 		}
+	} else {
+		return errors.Errorf(SubscriptionUnavailable, strings.TrimSuffix(repoWithOwner, "/"))
 	}
 
 	return nil

server/plugin/test_utils.go

@@ -1,3 +1,6 @@
+// Copyright (c) 2018-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
 package plugin
 
 import (