feat: All buffer previewers are now async and more config options (#354)

Configure preview window with:
autocmd User TelescopePreviewerLoaded setlocal wrap
autocmd User TelescopePreviewerLoaded setlocal number

file_maker example: Use regex highlighting for certain filetype like `*min.js` because they slow
down things with treesitter highlighter. Just a snippet for tests. We will do an extension :)

local previewers = require('telescope.previewers')
local putils = require('telescope.previewers.utils')
local pfiletype = require('plenary.filetype')

local _bad = { '.*%.min%.js' }
local bad_files = function(filepath)
  for _, v in ipairs(_bad) do
    if filepath:match(v) then
      return true
    end
  end

  return false
end

local new_maker = function(filepath, bufnr, bufname, use_ft_detect, callback)
  if use_ft_detect == nil then use_ft_detect = true end

  if bad_files(filepath) then
    previewers.buffer_previewer_maker(filepath, bufnr, bufname, false, callback)
    local ft = pfiletype.detect(filepath)
    putils.regex_highlighter(bufnr, ft)
  else
    previewers.buffer_previewer_maker(filepath, bufnr, bufname, use_ft_detect, callback)
  end
end

require('telescope').setup {
  defaults = {
    buffer_previewer_maker = new_maker,
  }
}

lua/telescope/previewers/utils.lua

@@ -1,5 +1,11 @@
 local context_manager = require('plenary.context_manager')
 
+local has_ts, _ = pcall(require, 'nvim-treesitter')
+local _, ts_highlight = pcall(require, 'nvim-treesitter.highlight')
+local _, ts_parsers = pcall(require, 'nvim-treesitter.parsers')
+
+local Job = require('plenary.job')
+
 local utils = {}
 
 utils.with_preview_window = function(status, bufnr, callable)
@@ -14,4 +20,50 @@ utils.with_preview_window = function(status, bufnr, callable)
   end
 end
 
+-- API helper functions for buffer previewer
+--- Job maker for buffer previewer
+utils.job_maker = function(cmd, env, value, bufnr, bufname, callback)
+  if bufname ~= value then
+    local command = table.remove(cmd, 1)
+    Job:new({
+      command = command,
+      args = cmd,
+      env = env,
+      on_exit = vim.schedule_wrap(function(j)
+        vim.api.nvim_buf_set_lines(bufnr, 0, -1, false, j:result())
+        if callback then callback(bufnr, j:result()) end
+      end)
+    }):start()
+  else
+    if callback then callback(bufnr) end
+  end
+end
+
+--- Attach default highlighter which will choose between regex and ts
+utils.highlighter = function(bufnr, ft)
+  if ft and ft ~= '' then
+    if has_ts and ts_parsers.has_parser(ft) then
+      ts_highlight.attach(bufnr, ft)
+    else
+      vim.cmd(':ownsyntax ' .. ft)
+    end
+  end
+end
+
+--- Attach regex highlighter
+utils.regex_highlighter = function(_, ft)
+  if ft and ft ~= '' then
+    vim.cmd(':ownsyntax ' .. ft)
+  end
+end
+
+-- Attach ts highlighter
+utils.ts_highlighter = function(bufnr, ft)
+  if ft and ft ~= '' then
+    if has_ts and ts_parsers.has_parser(ft) then
+      ts_highlight.attach(bufnr, ft)
+    end
+  end
+end
+
 return utils