Batch `onDidChangeTextDocument()` events

[RedCMD]

From the discussion at microsoft/vscode-discussions#1606

I would like to be able to query how many change events are queued up for onDidChangeTextDocument()
Then I can batch process parsing the document much more effectively

The recommended suggestion of using setTimeout() to debounce the input causes issues with symbol outline when autosave is turned off

[jrieken]

I would like to be able to query how many change events are queued up for onDidChangeTextDocument()

It is always 0 - we don't queue up document change events and send to the EH as soon as they happen

[RedCMD]

in that case
could VSCode batch document change events if parsing within onDidChangeTextDocument() takes a long time?

It is always 0

JS will queue it up tho won't it?

[jrieken]

No, we will never batch or queue them because all changes and request based on these changes must happen in order on the state the UI saw them.

[jrieken]

change events if parsing within onDidChangeTextDocument() takes a long time?

You should not take a long time. It will block the EH, meaning no message or event, can be processed. For long running, compute intense work you should use a worker thread

[RedCMD]

compute intense work you should use a worker thread

there is no way to tell VSCode that symbol outline has changed
currently if I return instantly from onDidChangeTextDocument() and autosave is turned off, outline will always be out of date

shall I make a bug report?

[jrieken]

No. The renderer will ask for new outline elements when it thinks the time is for that. This depends on debouncing inside the renderer and on how fast the extension actually computes those outline elements - if that's slow we ask less often, if that's fast we ask for less of a delay

[RedCMD]

so it's alright to block DocumentSymbolProvider() while the document is being parsed?

[jrieken]

No, it is never OK to block the EH thread - for expensive operations we should spawn a thread or shell out to a different process

[RedCMD]

what events trigger DocumentSymbolProvider()?
cause as far as I can tell, VSCode only ever requests Symbols after onDidChangeTextDocument() returns

(assuming computing the Symbols is near instant <5ms)
users edits document
VSCode fires onDidChangeTextDocument()
my extension spawns a thread and returns instantly

VSCode fires DocumentSymbolProvider()
my extension returns outdated Symbols (because the thread hasn't finished)

the thread finishes after taking its time reparsing the document 500ms+
I would expect Symbols to be updated
but VSCode doesn't fire DocumentSymbolProvider() (unless there is an autosave)
what do I have to do to get VSCode to re-request document Symbols?

maybe I'm missing something
but everytime I try to make reparsing 'async'/non-blocking
outline keeps being out of date
(when autosave is disabled)