Duplicate of first entry in navigation bar in custom Visual Studio Language Service

Question

I'm implementing a Visual Studio Language Service for a custom scripting language used internally at my company, and I've run into an issue with the navigation bar implemented as a subclass of TypeAndMemberDropdownBars. The subclass is created by my LanguageService subclass' LanguageService.CreateDropDownHelper method.

In the OnSynchronizeDropdowns method I'm iterating through the types defined in the file and adding DropDownMembers to the passed-in array to fill out the navigation bar. The issue I'm seeing is that the first item in the array is being duplicated and placed at the end of the listing by code that I don't have access to. This extra item does not behave correctly when selected (nothing happens), but doesn't seem to cause any other issues; the rest of the items in the list work fine. Additionally, this only seems to happen for the type dropdown box - the members dropdown box does not display this behavior.

I'm hoping someone else has seen and resolved this issue and could provide some assistance. Thanks!

Answer 1

Turns out this was caused by me calling LanguageService.SynchronizeDropdowns from my LanguageService.ParseSource method, which was being called on a background thread. I've fixed the problem by setting a flag when ParseSource does a Check parse, and then implementing a check for that flag in my LanguageService.OnIdle function that will call SynchronizeDropdowns. It's now working as expected!

Answer 2

A better solution is to implement the LanguageService.OnParseComplete callback, and call SynchronizeDropdowns from there. OnParseComplete is always called from the main thread, so this prevents any synchronization issues from coming up, and also keeps you from having to keep track of whether or not you need to call SynchronizeDropdowns().