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

server/plugin/command.go

@@ -599,8 +599,12 @@ 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 {
-		p.client.Log.Warn("Failed to unsubscribe", "repo", repo, "error", err.Error())
+	if sErr := p.Unsubscribe(args.ChannelId, repo, owner); sErr != nil {
+		if sErr.Code == SubscriptionNotFound {
+			return sErr.Error.Error()
+		}
+
+		p.client.Log.Warn("Failed to unsubscribe", "repo", repo, "error", sErr.Error.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 {
@@ -378,17 +379,32 @@ func (p *Plugin) GetSubscribedChannelsForRepository(repo *github.Repository) []*
 	return subsToReturn
 }
 
-func (p *Plugin) Unsubscribe(channelID, repo, owner string) error {
+type SubscriptionError struct {
+	Code  int
+	Error error
+}
+
+const (
+	SubscriptionNotFound = iota
+	SubscriptionAlreadyExists
+	InternalServerError
+)
+
+func NewSubscriptionError(code int, err error) *SubscriptionError {
+	return &SubscriptionError{Code: code, Error: err}
+}
+
+func (p *Plugin) Unsubscribe(channelID, repo, owner string) *SubscriptionError {
 	repoWithOwner := fmt.Sprintf("%s/%s", owner, repo)
 
 	subs, err := p.GetSubscriptions()
 	if err != nil {
-		return errors.Wrap(err, "could not get subscriptions")
+		return NewSubscriptionError(InternalServerError, errors.Wrap(err, "could not get subscriptions"))
 	}
 
 	repoSubs := subs.Repositories[repoWithOwner]
 	if repoSubs == nil {
-		return nil
+		return NewSubscriptionError(SubscriptionNotFound, errors.Errorf(SubscriptionUnavailable, strings.TrimSuffix(repoWithOwner, "/")))
 	}
 
 	removed := false
@@ -400,11 +416,13 @@ func (p *Plugin) Unsubscribe(channelID, repo, owner string) error {
 		}
 	}
 
-	if removed {
-		subs.Repositories[repoWithOwner] = repoSubs
-		if err := p.StoreSubscriptions(subs); err != nil {
-			return errors.Wrap(err, "could not store subscriptions")
-		}
+	if !removed {
+		return NewSubscriptionError(SubscriptionNotFound, errors.Errorf(SubscriptionUnavailable, strings.TrimSuffix(repoWithOwner, "/")))
+	}
+
+	subs.Repositories[repoWithOwner] = repoSubs
+	if err := p.StoreSubscriptions(subs); err != nil {
+		return NewSubscriptionError(InternalServerError, errors.Wrap(err, "could not store subscriptions"))
 	}
 
 	return nil