feat(performance): Major performance improvements using async v2 from @oberblastmeister (#987)

* start: Working w/ async jobs

* short circuit to using bad finder if you pass writer.

lua/telescope/finders/async_oneshot_finder.lua

@@ -1,14 +1,9 @@
-local async_lib = require "plenary.async_lib"
-local async = async_lib.async
-local await = async_lib.await
-local void = async_lib.void
-
-local AWAITABLE = 1000
+local async = require "plenary.async"
+local async_job = require "telescope._"
+local LinesPipe = require("telescope._").LinesPipe
 
 local make_entry = require "telescope.make_entry"
 
-local Job = require "plenary.job"
-
 return function(opts)
   opts = opts or {}
 
@@ -21,64 +16,65 @@ return function(opts)
 
   local job_started = false
   local job_completed = false
+  local stdout = nil
+
   return setmetatable({
-    close = function()
-      results = {}
-      job_started = false
-    end,
+    -- close = function() results = {}; job_started = false end,
+    close = function() end,
     results = results,
   }, {
-    __call = void(async(function(_, prompt, process_result, process_complete)
+    __call = function(_, prompt, process_result, process_complete)
       if not job_started then
         local job_opts = fn_command()
 
-        local writer
-        if job_opts.writer and Job.is_job(job_opts.writer) then
-          writer = job_opts.writer
-        elseif job_opts.writer then
-          writer = Job:new(job_opts.writer)
-        end
+        -- TODO: Handle writers.
+        -- local writer
+        -- if job_opts.writer and Job.is_job(job_opts.writer) then
+        --   writer = job_opts.writer
+        -- elseif job_opts.writer then
+        --   writer = Job:new(job_opts.writer)
+        -- end
 
-        local job = Job:new {
+        stdout = LinesPipe()
+        local _ = async_job.spawn {
           command = job_opts.command,
           args = job_opts.args,
-          cwd = job_opts.cwd or cwd,
-          maximum_results = opts.maximum_results,
-          writer = writer,
-          enable_recording = false,
+          cwd = cwd,
 
-          on_stdout = vim.schedule_wrap(function(_, line)
-            num_results = num_results + 1
-
-            local v = entry_maker(line)
-            results[num_results] = v
-            process_result(v)
-          end),
-
-          on_exit = function()
-            process_complete()
-            job_completed = true
-          end,
+          stdout = stdout,
         }
 
-        job:start()
         job_started = true
       end
 
+      if not job_completed then
+        for line in stdout:iter(true) do
+          num_results = num_results + 1
+
+          local v = entry_maker(line)
+          results[num_results] = v
+          process_result(v)
+        end
+
+        process_complete()
+        job_completed = true
+
+        return
+      end
+
       local current_count = num_results
       for index = 1, current_count do
+        -- TODO: Figure out scheduling...
+        async.util.scheduler()
+
         if process_result(results[index]) then
           break
         end
-
-        if index % AWAITABLE == 0 then
-          await(async_lib.scheduler())
-        end
       end
 
       if job_completed then
         process_complete()
       end
-    end)),
+    end,
   })
 end