perf(trash_windows): use a single powershell instance for operations

[TheLeoP]

As mentioned in #243, trash support on windows is slow for some operations because it spawns a powershell process for every operation (sending 10 files to trash would spawn 10 powershell instances).

This PR starts two powershell intances (one for listing and one for deleting) and communicates with them over stdio (sending 10 files to trash now spawns only 1 powershell instance).

This improves the performance of trash related operations in windows after the first operation (because it's neccesary to start the powershell instance the first time). Maybe it could be preffered to start the powershell instances on startup instead (?).

[stevearc]

With all the global (module-local) variables, this starts to get difficult to reason about. I'm pretty sure there are race conditions here if one of the methods gets called in quick succession. What I'd like to see is a refactoring to push this new added complexity into a self-contained file that exposes a clean API for this trash adapter to delete and restore files. You can take a look at what I'm doing for SSH connections, because it's very similar. In particular, look at this section

oil.nvim/lua/oil/adapters/ssh/connection.lua

Lines 285 to 312 in c4cc824

	---@param command string
	---@param callback fun(err: nil|string, lines: nil|string[])
	function SSHConnection:run(command, callback)
	if self.connection_error then
	callback(self.connection_error)
	else
	table.insert(self.commands, { cmd = command, cb = callback })
	self:_consume()
	end
	end
	function SSHConnection:_consume()
	if self.connected and not vim.tbl_isempty(self.commands) then
	local cmd = self.commands[1]
	if not cmd.running then
	cmd.running = true
	vim.api.nvim_chan_send(
	self.jid,
	-- HACK: Sleep briefly to help reduce stderr/stdout interleaving.
	-- I want to find a way to flush the stderr before the echo DONE, but haven't yet.
	-- This was causing issues when ls directory that doesn't exist (b/c ls prints error)
	'echo "===BEGIN==="; '
	.. cmd.cmd
	.. '; CODE=$?; sleep .01; echo "===DONE($CODE)==="\r'
	)
	end
	end
	end

This ensures that the commands get executed sequentially because there's no way for a single process to do two at once.

[TheLeoP]

Is this approach ok? I'm not sure about how the initial command are handled (I tried to use coroutines, but got an error because they can't be used across c call boundaries). Also, the API isn't trash specific, would an trash specific API be preffered?

[stevearc]

This already looks better! I think for this particular case I'd like to see even more of the powershell trash logic pulled out into a different file. Right now the logic for "check if powershell job is running, create one if not" lives in the windows trash adapter file, and it just makes it a little cluttered. It's already a pretty long file with a decent amount of complexity surrounding trash semantics; it would be nice to put all the complexity of managing long-lived jobs into a different file.

[TheLeoP]

I didn't undestand how _consume was suppossed to work inside the on_stdout callback and your comment made it click for me. This allowed me to simplify the initialization code a lot. Is it better? Or would it still be preffered to extract it into a different file?

[stevearc]

I shuffled around some of the logic. LMK if this makes sense (and if it still works for you)

[TheLeoP]

Looks good to me and it's working as expected c: