PLT-3560 blocking adding to channel once user is removed (#3537)

api/channel.go

@@ -562,6 +562,11 @@ func AddUserToChannel(user *model.User, channel *model.Channel) (*model.ChannelM
 
 	if result := <-tmchan; result.Err != nil {
 		return nil, result.Err
+	} else {
+		teamMember := result.Data.(model.TeamMember)
+		if teamMember.DeleteAt > 0 {
+			return nil, model.NewLocAppError("AddUserToChannel", "api.channel.add_user.to.channel.failed.deleted.app_error", nil, "")
+		}
 	}
 
 	if result := <-cmchan; result.Err != nil {

api/channel_test.go

@@ -833,6 +833,25 @@ func TestJoinChannelByName(t *testing.T) {
 	}
 }
 
+func TestJoinChannelByNameDisabledUser(t *testing.T) {
+	th := Setup().InitBasic()
+	Client := th.BasicClient
+	team := th.BasicTeam
+
+	channel1 := &model.Channel{DisplayName: "A Test API Name", Name: "a" + model.NewId() + "a", Type: model.CHANNEL_OPEN, TeamId: team.Id}
+	channel1 = Client.Must(Client.CreateChannel(channel1)).Data.(*model.Channel)
+
+	Client.Must(th.BasicClient.RemoveUserFromTeam(th.BasicTeam.Id, th.BasicUser.Id))
+
+	if _, err := AddUserToChannel(th.BasicUser, channel1); err == nil {
+		t.Fatal("shoudn't be able to join channel")
+	} else {
+		if err.Id != "api.channel.add_user.to.channel.failed.deleted.app_error" {
+			t.Fatal("wrong error")
+		}
+	}
+}
+
 func TestLeaveChannel(t *testing.T) {
 	th := Setup().InitBasic()
 	Client := th.BasicClient

i18n/en.json

@@ -163,6 +163,10 @@
     "id": "api.channel.add_user.to.channel.failed.app_error",
     "translation": "Failed to add user to channel"
   },
+  {
+    "id": "api.channel.add_user.to.channel.failed.deleted.app_error",
+    "translation": "Failed to add user to channel because they have been removed from the team."
+  },
   {
     "id": "api.channel.add_user_to_channel.deleted.app_error",
     "translation": "The channel has been archived or deleted"