Refactor previewers (#345)

lua/telescope/previewers/buffer_previewer.lua

@@ -0,0 +1,488 @@
+local debounce = require('telescope.debounce')
+local from_entry = require('telescope.from_entry')
+local path = require('telescope.path')
+local utils = require('telescope.utils')
+local putils = require('telescope.previewers.utils')
+local Previewer = require('telescope.previewers.previewer')
+
+local pfiletype = require('plenary.filetype')
+
+local has_ts, _ = pcall(require, 'nvim-treesitter')
+local _, ts_highlight = pcall(require, 'nvim-treesitter.highlight')
+local _, ts_parsers = pcall(require, 'nvim-treesitter.parsers')
+
+local buf_delete = utils.buf_delete
+
+local defaulter = utils.make_default_callable
+
+local previewers = {}
+
+local previewer_ns = vim.api.nvim_create_namespace('telescope.previewers')
+
+local file_maker_async = function(filepath, bufnr, bufname, callback)
+  local ft = pfiletype.detect(filepath)
+
+  if bufname ~= filepath then
+    path.read_file_async(filepath, vim.schedule_wrap(function(data)
+      vim.api.nvim_buf_set_lines(bufnr, 0, -1, false, vim.split(data, "\n"))
+
+      if callback then callback() end
+    end))
+  else
+    if callback then callback() end
+  end
+
+  if 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
+
+local file_maker_sync = function(filepath, bufnr, bufname)
+  local ft = pfiletype.detect(filepath)
+  if bufname ~= filepath then
+    local data = path.read_file(filepath)
+    vim.api.nvim_buf_set_lines(bufnr, 0, -1, false, vim.split(data, "\n"))
+  end
+
+  if 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
+
+previewers.new_buffer_previewer = function(opts)
+  opts = opts or {}
+
+  assert(opts.define_preview, "define_preview is a required function")
+  assert(not opts.preview_fn, "preview_fn not allowed")
+
+  local opt_setup = opts.setup
+  local opt_teardown = opts.teardown
+
+  local old_bufs = {}
+  local bufname_table = {}
+
+  local function get_bufnr(self)
+    if not self.state then return nil end
+    return self.state.bufnr
+  end
+
+  local function set_bufnr(self, value)
+    if get_bufnr(self) then table.insert(old_bufs, get_bufnr(self)) end
+    if self.state then self.state.bufnr = value end
+  end
+
+  local function get_bufnr_by_bufname(self, value)
+    if not self.state then return nil end
+    return bufname_table[value]
+  end
+
+  local function set_bufname(self, value)
+    if get_bufnr(self) then bufname_table[value] = get_bufnr(self) end
+    if self.state then self.state.bufname = value end
+  end
+
+  function opts.setup(self)
+    local state = {}
+    if opt_setup then vim.tbl_deep_extend("force", state, opt_setup(self)) end
+    return state
+  end
+
+  function opts.teardown(self)
+    if opt_teardown then
+      opt_teardown(self)
+    end
+
+    set_bufnr(self, nil)
+    set_bufname(self, nil)
+
+    for _, bufnr in ipairs(old_bufs) do
+      buf_delete(bufnr)
+    end
+  end
+
+  function opts.preview_fn(self, entry, status)
+    if get_bufnr(self) == nil then
+      set_bufnr(self, vim.api.nvim_win_get_buf(status.preview_win))
+    end
+
+    if opts.get_buffer_by_name and get_bufnr_by_bufname(self, opts.get_buffer_by_name(self, entry)) then
+      self.state.bufname = opts.get_buffer_by_name(self, entry)
+      self.state.bufnr = get_bufnr_by_bufname(self, self.state.bufname)
+      vim.api.nvim_win_set_buf(status.preview_win, self.state.bufnr)
+    else
+      local bufnr = vim.api.nvim_create_buf(false, true)
+      set_bufnr(self, bufnr)
+
+      vim.api.nvim_win_set_buf(status.preview_win, bufnr)
+
+      -- TODO(conni2461): We only have to set options once. Right?
+      vim.api.nvim_win_set_option(status.preview_win, 'winhl', 'Normal:Normal')
+      vim.api.nvim_win_set_option(status.preview_win, 'signcolumn', 'no')
+      vim.api.nvim_win_set_option(status.preview_win, 'foldlevel', 100)
+      vim.api.nvim_win_set_option(status.preview_win, 'scrolloff', 999)
+      vim.api.nvim_win_set_option(status.preview_win, 'wrap', false)
+
+      self.state.winid = status.preview_win
+      self.state.bufname = nil
+    end
+
+    opts.define_preview(self, entry, status)
+
+    if opts.get_buffer_by_name then
+      set_bufname(self, opts.get_buffer_by_name(self, entry))
+    end
+  end
+
+  if not opts.scroll_fn then
+    function opts.scroll_fn(self, direction)
+      local input = direction > 0 and "d" or "u"
+      local count = math.abs(direction)
+
+      self:send_input({ count = count, input = input })
+    end
+  end
+
+  if not opts.send_input then
+    function opts.send_input(self, input)
+      if not self.state then
+        return
+      end
+
+      local max_line = vim.fn.getbufinfo(self.state.bufnr)[1].linecount
+      local line = vim.api.nvim_win_get_cursor(self.state.winid)[1]
+      if input.input == 'u' then
+        line = (line - input.count) > 0 and (line - input.count) or 1
+      else
+        line = (line + input.count) <= max_line and (line + input.count) or max_line
+      end
+      vim.api.nvim_win_set_cursor(self.state.winid, { line, 1 })
+    end
+  end
+
+  return Previewer:new(opts)
+end
+
+previewers.cat = defaulter(function(_)
+  return previewers.new_buffer_previewer {
+    get_buffer_by_name = function(_, entry)
+      return from_entry.path(entry, true)
+    end,
+
+    define_preview = function(self, entry, status)
+      putils.with_preview_window(status, nil, function()
+        local p = from_entry.path(entry, true)
+        if p == nil or p == '' then return end
+        file_maker_async(p, self.state.bufnr, self.state.bufname)
+      end)
+    end
+  }
+end, {})
+
+previewers.vimgrep = defaulter(function(_)
+  return previewers.new_buffer_previewer {
+    setup = function()
+      return {
+        last_set_bufnr = nil
+      }
+    end,
+
+    teardown = function(self)
+      if self.state and self.state.last_set_bufnr and vim.api.nvim_buf_is_valid(self.state.last_set_bufnr) then
+        vim.api.nvim_buf_clear_namespace(self.state.last_set_bufnr, previewer_ns, 0, -1)
+      end
+    end,
+
+    get_buffer_by_name = function(_, entry)
+      return from_entry.path(entry, true)
+    end,
+
+    define_preview = function(self, entry, status)
+      putils.with_preview_window(status, nil, function()
+        local lnum = entry.lnum or 0
+        local p = from_entry.path(entry, true)
+        if p == nil or p == '' then return end
+
+        file_maker_sync(p, self.state.bufnr, self.state.bufname)
+
+        if lnum ~= 0 then
+          if self.state.last_set_bufnr then
+            pcall(vim.api.nvim_buf_clear_namespace, self.state.last_set_bufnr, previewer_ns, 0, -1)
+          end
+          pcall(vim.api.nvim_buf_add_highlight, self.state.bufnr, previewer_ns, "TelescopePreviewLine", lnum - 1, 0, -1)
+          pcall(vim.api.nvim_win_set_cursor, status.preview_win, {lnum, 0})
+        end
+
+        self.state.last_set_bufnr = self.state.bufnr
+      end)
+    end
+  }
+end, {})
+
+previewers.qflist = previewers.vimgrep
+
+previewers.ctags = defaulter(function(_)
+  return previewers.new_buffer_previewer {
+    teardown = function(self)
+      if self.state and self.state.hl_id then
+        pcall(vim.fn.matchdelete, self.state.hl_id, self.state.hl_win)
+        self.state.hl_id = nil
+      end
+    end,
+
+    get_buffer_by_name = function(_, entry)
+      return entry.filename
+    end,
+
+    define_preview = function(self, entry, status)
+      putils.with_preview_window(status, nil, function()
+        local scode = string.gsub(entry.scode, '[$]$', '')
+        scode = string.gsub(scode, [[\\]], [[\]])
+        scode = string.gsub(scode, [[\/]], [[/]])
+        scode = string.gsub(scode, '[*]', [[\*]])
+
+        file_maker_sync(entry.filename, self.state.bufnr, self.state.bufname)
+
+        pcall(vim.fn.matchdelete, self.state.hl_id, self.state.winid)
+        vim.cmd "norm! gg"
+        vim.fn.search(scode)
+
+        self.state.hl_id = vim.fn.matchadd('TelescopePreviewMatch', scode)
+      end)
+    end
+  }
+end, {})
+
+previewers.builtin = defaulter(function(_)
+  return previewers.new_buffer_previewer {
+    setup = function()
+      return {}
+    end,
+
+    teardown = function(self)
+      if self.state and self.state.hl_id then
+        pcall(vim.fn.matchdelete, self.state.hl_id, self.state.hl_win)
+        self.state.hl_id = nil
+      end
+    end,
+
+    get_buffer_by_name = function(_, entry)
+      return entry.filename
+    end,
+
+    define_preview = function(self, entry, status)
+      putils.with_preview_window(status, nil, function()
+        local module_name = vim.fn.fnamemodify(entry.filename, ':t:r')
+        local text
+        if entry.text:sub(1, #module_name) ~= module_name then
+          text = module_name .. '.' .. entry.text
+        else
+          text = entry.text:gsub('_', '.', 1)
+        end
+
+        file_maker_sync(entry.filename, self.state.bufnr, self.state.bufname)
+
+        pcall(vim.fn.matchdelete, self.state.hl_id, self.state.winid)
+        vim.cmd "norm! gg"
+        vim.fn.search(text)
+
+        self.state.hl_id = vim.fn.matchadd('TelescopePreviewMatch', text)
+      end)
+    end
+  }
+end, {})
+
+previewers.help = defaulter(function(_)
+  return previewers.new_buffer_previewer {
+    setup = function()
+      return {}
+    end,
+
+    teardown = function(self)
+      if self.state and self.state.hl_id then
+        pcall(vim.fn.matchdelete, self.state.hl_id, self.state.hl_win)
+        self.state.hl_id = nil
+      end
+    end,
+
+    get_buffer_by_name = function(_, entry)
+      return entry.filename
+    end,
+
+    define_preview = function(self, entry, status)
+      putils.with_preview_window(status, nil, function()
+        local query = entry.cmd
+        query = query:sub(2)
+        query = [[\V]] .. query
+
+        file_maker_sync(entry.filename, self.state.bufnr, self.state.bufname)
+        vim.cmd(':ownsyntax help')
+
+        pcall(vim.fn.matchdelete, self.state.hl_id, self.state.winid)
+        vim.cmd "norm! gg"
+        vim.fn.search(query, "W")
+
+        self.state.hl_id = vim.fn.matchadd('TelescopePreviewMatch', query)
+      end)
+    end
+  }
+end, {})
+
+previewers.man = defaulter(function(_)
+  return previewers.new_buffer_previewer {
+    define_preview = debounce.throttle_leading(function(self, entry, status)
+      putils.with_preview_window(status, nil, function()
+        local cmd = entry.value
+        local man_value = vim.fn['man#goto_tag'](cmd, '', '')
+        if #man_value == 0 then
+          print("No value for:", cmd)
+          return
+        end
+
+        local filename = man_value[1].filename
+        if vim.api.nvim_buf_get_name(0) == filename then
+          return
+        end
+
+        vim.api.nvim_command('view ' .. filename)
+
+        vim.api.nvim_buf_set_option(self.state.bufnr, 'buftype', 'nofile')
+        vim.api.nvim_buf_set_option(self.state.bufnr, 'bufhidden', 'hide')
+        vim.api.nvim_buf_set_option(self.state.bufnr, 'swapfile', false)
+        vim.api.nvim_buf_set_option(self.state.bufnr, 'buflisted', false)
+      end)
+    end, 5)
+  }
+end)
+
+previewers.autocommands = defaulter(function(_)
+  return previewers.new_buffer_previewer {
+    teardown = function(self)
+      if self.state and self.state.last_set_bufnr and vim.api.nvim_buf_is_valid(self.state.last_set_bufnr) then
+        pcall(vim.api.nvim_buf_clear_namespace, self.state.last_set_bufnr, previewer_ns, 0, -1)
+      end
+    end,
+
+    get_buffer_by_name = function(_, entry)
+      return entry.group
+    end,
+
+    define_preview = function(self, entry, status)
+      local results = vim.tbl_filter(function (x)
+        return x.group == entry.group
+      end, status.picker.finder.results)
+
+      if self.state.last_set_bufnr then
+        pcall(vim.api.nvim_buf_clear_namespace, self.state.last_set_bufnr, previewer_ns, 0, -1)
+      end
+
+      local selected_row = 0
+      if self.state.bufname ~= entry.group then
+        local display = {}
+        table.insert(display, string.format(" augroup: %s - [ %d entries ]", entry.group, #results))
+        -- TODO: calculate banner width/string in setup()
+        -- TODO: get column characters to be the same HL group as border
+        table.insert(display, string.rep("─", vim.fn.getwininfo(status.preview_win)[1].width))
+
+        for idx, item in ipairs(results) do
+          if item == entry then
+            selected_row = idx
+          end
+          table.insert(display,
+            string.format("  %-14s▏%-08s %s", item.event, item.ft_pattern, item.command)
+          )
+        end
+
+        vim.api.nvim_buf_set_option(self.state.bufnr, "filetype", "vim")
+        vim.api.nvim_buf_set_lines(self.state.bufnr, 0, -1, false, display)
+        vim.api.nvim_buf_add_highlight(self.state.bufnr, 0, "TelescopeBorder", 1, 0, -1)
+      else
+        for idx, item in ipairs(results) do
+          if item == entry then
+            selected_row = idx
+            break
+          end
+        end
+      end
+
+      vim.api.nvim_buf_add_highlight(self.state.bufnr, previewer_ns, "TelescopePreviewLine", selected_row + 1, 0, -1)
+      vim.api.nvim_win_set_cursor(status.preview_win, {selected_row + 1, 0})
+
+      self.state.last_set_bufnr = self.state.bufnr
+    end,
+  }
+end, {})
+
+previewers.highlights = defaulter(function(_)
+  return previewers.new_buffer_previewer {
+    teardown = function(self)
+      if self.state and self.state.last_set_bufnr and vim.api.nvim_buf_is_valid(self.state.last_set_bufnr) then
+        vim.api.nvim_buf_clear_namespace(self.state.last_set_bufnr, previewer_ns, 0, -1)
+      end
+    end,
+
+    get_buffer_by_name = function(_, entry)
+      return "highlights"
+    end,
+
+    define_preview = function(self, entry, status)
+      putils.with_preview_window(status, nil, function()
+        if not self.state.bufname then
+          local output = vim.split(vim.fn.execute('highlight'), '\n')
+          local hl_groups = {}
+          for _, v in ipairs(output) do
+            if v ~= '' then
+              if v:sub(1, 1) == ' ' then
+                local part_of_old = v:match('%s+(.*)')
+                hl_groups[table.getn(hl_groups)] = hl_groups[table.getn(hl_groups)] .. part_of_old
+              else
+                table.insert(hl_groups, v)
+              end
+            end
+          end
+
+          vim.api.nvim_buf_set_lines(self.state.bufnr, 0, -1, false, hl_groups)
+          for k, v in ipairs(hl_groups) do
+            local startPos = string.find(v, 'xxx', 1, true) - 1
+            local endPos = startPos + 3
+            local hlgroup = string.match(v, '([^ ]*)%s+.*')
+            pcall(vim.api.nvim_buf_add_highlight, self.state.bufnr, 0, hlgroup, k - 1, startPos, endPos)
+          end
+        end
+
+        pcall(vim.api.nvim_buf_clear_namespace, self.state.bufnr, previewer_ns, 0, -1)
+        vim.cmd "norm! gg"
+        vim.fn.search(entry.value .. ' ')
+        local lnum = vim.fn.line('.')
+        -- That one is actually a match but its better to use it like that then matchadd
+        vim.api.nvim_buf_add_highlight(self.state.bufnr,
+          previewer_ns,
+          "TelescopePreviewMatch",
+          lnum - 1,
+          0,
+          #entry.value)
+      end)
+    end,
+  }
+end, {})
+
+previewers.display_content = defaulter(function(_)
+  return previewers.new_buffer_previewer {
+    define_preview = function(self, entry, status)
+      putils.with_preview_window(status, nil, function()
+        assert(type(entry.preview_command) == 'function',
+               'entry must provide a preview_command function which will put the content into the buffer')
+        entry.preview_command(entry, self.state.bufnr)
+      end)
+    end
+  }
+end, {})
+
+return previewers

lua/telescope/previewers/init.lua

@@ -0,0 +1,33 @@
+local Previewer = require('telescope.previewers.previewer')
+local term_previewer = require('telescope.previewers.term_previewer')
+local buffer_previewer = require('telescope.previewers.buffer_previewer')
+
+local previewers = {}
+
+previewers.new = function(...)
+  return Previewer:new(...)
+end
+
+previewers.new_termopen_previewer = term_previewer.new_termopen_previewer
+previewers.git_commit_diff        = term_previewer.git_commit_diff
+previewers.git_branch_log         = term_previewer.git_branch_log
+previewers.git_file_diff          = term_previewer.git_file_diff
+previewers.cat                    = term_previewer.cat
+previewers.vimgrep                = term_previewer.vimgrep
+previewers.qflist                 = term_previewer.qflist
+
+previewers.new_buffer_previewer = buffer_previewer.new_buffer_previewer
+previewers.vim_buffer_cat       = buffer_previewer.cat
+previewers.vim_buffer_vimgrep   = buffer_previewer.vimgrep
+previewers.vim_buffer_qflist    = buffer_previewer.qflist
+previewers.ctags                = buffer_previewer.ctags
+previewers.builtin              = buffer_previewer.builtin
+previewers.help                 = buffer_previewer.help
+previewers.man                  = buffer_previewer.man
+previewers.autocommands         = buffer_previewer.autocommands
+previewers.highlights           = buffer_previewer.highlights
+previewers.display_content      = buffer_previewer.display_content
+
+previewers.Previewer = Previewer
+
+return previewers

lua/telescope/previewers/previewer.lua

@@ -0,0 +1,55 @@
+local Previewer = {}
+Previewer.__index = Previewer
+
+function Previewer:new(opts)
+  opts = opts or {}
+
+  return setmetatable({
+    state = nil,
+    _setup_func = opts.setup,
+    _teardown_func = opts.teardown,
+    _send_input = opts.send_input,
+    _scroll_fn = opts.scroll_fn,
+    preview_fn = opts.preview_fn,
+  }, Previewer)
+end
+
+function Previewer:preview(entry, status)
+  if not entry then
+    return
+  end
+
+  if not self.state then
+    if self._setup_func then
+      self.state = self:_setup_func()
+    else
+      self.state = {}
+    end
+  end
+
+  return self:preview_fn(entry, status)
+end
+
+function Previewer:teardown()
+  if self._teardown_func then
+    self:_teardown_func()
+  end
+end
+
+function Previewer:send_input(input)
+  if self._send_input then
+    self:_send_input(input)
+  else
+    vim.api.nvim_err_writeln("send_input is not defined for this previewer")
+  end
+end
+
+function Previewer:scroll_fn(direction)
+  if self._scroll_fn then
+    self:_scroll_fn(direction)
+  else
+    vim.api.nvim_err_writeln("scroll_fn is not defined for this previewer")
+  end
+end
+
+return Previewer

lua/telescope/previewers/term_previewer.lua

@@ -0,0 +1,320 @@
+local conf = require('telescope.config').values
+local utils = require('telescope.utils')
+local putils = require('telescope.previewers.utils')
+local from_entry = require('telescope.from_entry')
+local Previewer = require('telescope.previewers.previewer')
+
+local flatten = vim.tbl_flatten
+local buf_delete = utils.buf_delete
+local job_is_running = utils.job_is_running
+
+local defaulter = utils.make_default_callable
+
+local previewers = {}
+
+-- TODO: Should play with these some more, ty @clason
+local bat_options = {"--style=plain", "--color=always", "--paging=always"}
+local has_less = (vim.fn.executable('less') == 1) and conf.use_less
+local termopen_env = vim.tbl_extend("force", { ['GIT_PAGER'] = (has_less and 'less' or '') }, conf.set_env)
+
+-- TODO(conni2461): Workaround for neovim/neovim#11751. Add only quotes when using else branch.
+local valuate_shell = function()
+  local shell = vim.o.shell
+  if string.find(shell, 'powershell.exe') or string.find(shell, 'cmd.exe') then
+    return ''
+  else
+    return "'"
+  end
+end
+
+local add_quotes = valuate_shell()
+
+local get_file_stat = function(filename)
+  return vim.loop.fs_stat(vim.fn.expand(filename)) or {}
+end
+
+local bat_maker = function(filename, lnum, start, finish)
+  if get_file_stat(filename).type == 'directory' then
+    return { 'ls', '-la', vim.fn.expand(filename) }
+  end
+
+  local command = {"bat"}
+  local theme = os.getenv("BAT_THEME")
+
+  if lnum then
+    table.insert(command, { "--highlight-line", lnum})
+  end
+
+  if has_less then
+    if start then
+      table.insert(command, {"--pager", string.format("%sless -RS +%s%s", add_quotes, start, add_quotes)})
+    else
+      table.insert(command, {"--pager", string.format("%sless -RS%s", add_quotes, add_quotes)})
+    end
+  else
+    if start and finish then
+      table.insert(command, { "-r", string.format("%s:%s", start, finish) })
+    end
+  end
+
+  if theme ~= nil then
+    table.insert(command, { "--theme", string.format("%s", vim.fn.shellescape(theme)) })
+  end
+
+  return flatten {
+    command, bat_options, "--", add_quotes .. vim.fn.expand(filename) .. add_quotes
+  }
+end
+
+local cat_maker = function(filename, _, start, _)
+  if get_file_stat(filename).type == 'directory' then
+    return { 'ls', '-la', add_quotes .. vim.fn.expand(filename) .. add_quotes }
+  end
+
+  if 1 == vim.fn.executable('file') then
+    local output = utils.get_os_command_output('file --mime-type -b ' .. filename)
+    local mime_type = vim.split(output, '/')[1]
+    if mime_type ~= "text" then
+      return { "echo", "Binary file found. These files cannot be displayed!" }
+    end
+  end
+
+  if has_less then
+    if start then
+      return { 'less', '-RS', string.format('+%s', start), add_quotes .. vim.fn.expand(filename) .. add_quotes }
+    else
+      return { 'less', '-RS', add_quotes .. vim.fn.expand(filename) .. add_quotes }
+    end
+  else
+    return {
+      "cat", "--", add_quotes .. vim.fn.expand(filename) .. add_quotes
+    }
+  end
+end
+
+local get_maker = function(opts)
+  local maker = opts.maker
+  if not maker and 1 == vim.fn.executable("bat") then
+    maker = bat_maker
+  elseif not maker and 1 == vim.fn.executable("cat") then
+    maker = cat_maker
+  end
+
+  if not maker then
+    error("Needs maker")
+  end
+
+  return maker
+end
+
+-- TODO: We shoudl make sure that all our terminals close all the way.
+--          Otherwise it could be bad if they're just sitting around, waiting to be closed.
+--          I don't think that's the problem, but it could be?
+previewers.new_termopen_previewer = function(opts)
+  opts = opts or {}
+
+  assert(opts.get_command, "get_command is a required function")
+  assert(not opts.preview_fn, "preview_fn not allowed")
+
+  local opt_setup = opts.setup
+  local opt_teardown = opts.teardown
+
+  local old_bufs = {}
+
+  local function get_term_id(self)
+    if not self.state then return nil end
+    return self.state.termopen_id
+  end
+
+  local function get_bufnr(self)
+    if not self.state then return nil end
+    return self.state.termopen_bufnr
+  end
+
+  local function set_term_id(self, value)
+    if job_is_running(get_term_id(self)) then vim.fn.jobstop(get_term_id(self)) end
+    if self.state then self.state.termopen_id = value end
+  end
+
+  local function set_bufnr(self, value)
+    if get_bufnr(self) then table.insert(old_bufs, get_bufnr(self)) end
+    if self.state then self.state.termopen_bufnr = value end
+  end
+
+  function opts.setup(self)
+    local state = {}
+    if opt_setup then vim.tbl_deep_extend("force", state, opt_setup(self)) end
+    return state
+  end
+
+  function opts.teardown(self)
+    if opt_teardown then
+      opt_teardown(self)
+    end
+
+    local term_id = get_term_id(self)
+    if term_id and utils.job_is_running(term_id) then
+      vim.fn.jobclose(term_id)
+    end
+
+    set_term_id(self, nil)
+    set_bufnr(self, nil)
+
+    for _, bufnr in ipairs(old_bufs) do
+      buf_delete(bufnr)
+    end
+  end
+
+  function opts.preview_fn(self, entry, status)
+    if get_bufnr(self) == nil then
+      set_bufnr(self, vim.api.nvim_win_get_buf(status.preview_win))
+    end
+
+    set_bufnr(self, vim.api.nvim_create_buf(false, true))
+
+    local bufnr = get_bufnr(self)
+    vim.api.nvim_win_set_buf(status.preview_win, bufnr)
+
+    local term_opts = {
+      cwd = opts.cwd or vim.fn.getcwd(),
+      env = termopen_env
+    }
+
+    -- TODO(conni2461): Workaround for neovim/neovim#11751.
+    local get_cmd = function(st)
+      local shell = vim.o.shell
+      if string.find(shell, 'powershell.exe') or string.find(shell, 'cmd.exe') then
+        return opts.get_command(entry, st)
+      else
+        local env = {}
+        for k, v in pairs(termopen_env) do
+          table.insert(env, k .. '=' .. v)
+        end
+        return table.concat(env, ' ') .. ' ' .. table.concat(opts.get_command(entry, st), ' ')
+      end
+    end
+
+    putils.with_preview_window(status, bufnr, function()
+      set_term_id(self, vim.fn.termopen(get_cmd(status), term_opts))
+    end)
+
+    vim.api.nvim_buf_set_name(bufnr, tostring(bufnr))
+  end
+
+  if not opts.send_input then
+    function opts.send_input(self, input)
+      local termcode = vim.api.nvim_replace_termcodes(input, true, false, true)
+
+      local term_id = get_term_id(self)
+      if term_id then
+        vim.fn.chansend(term_id, termcode)
+      end
+    end
+  end
+
+  if not opts.scroll_fn then
+    function opts.scroll_fn(self, direction)
+      if not self.state then
+        return
+      end
+
+      local input = direction > 0 and "d" or "u"
+      local count = math.abs(direction)
+
+      self:send_input(count..input)
+    end
+  end
+
+  return Previewer:new(opts)
+end
+
+previewers.git_commit_diff = defaulter(function(_)
+  return previewers.new_termopen_previewer {
+    get_command = function(entry)
+      local sha = entry.value
+      return { 'git', '-p', 'diff', sha .. '^!' }
+    end
+  }
+end, {})
+
+previewers.git_branch_log = defaulter(function(_)
+  return previewers.new_termopen_previewer {
+    get_command = function(entry)
+      return { 'git', '-p', 'log', '--graph',
+               "--pretty=format:" .. add_quotes .. "%Cred%h%Creset -%C(yellow)%d%Creset %s %Cgreen(%cr)%Creset"
+               .. add_quotes,
+               '--abbrev-commit', '--date=relative', entry.value }
+    end
+  }
+end, {})
+
+previewers.git_file_diff = defaulter(function(_)
+  return previewers.new_termopen_previewer {
+    get_command = function(entry)
+      return { 'git', '-p', 'diff', entry.value }
+    end
+  }
+end, {})
+
+previewers.cat = defaulter(function(opts)
+  local maker = get_maker(opts)
+
+  return previewers.new_termopen_previewer {
+    get_command = function(entry)
+      local p = from_entry.path(entry, true)
+      if p == nil or p == '' then return end
+
+      return maker(p)
+    end
+  }
+end, {})
+
+previewers.vimgrep = defaulter(function(opts)
+  local maker = get_maker(opts)
+
+  return previewers.new_termopen_previewer {
+    get_command = function(entry, status)
+      local win_id = status.preview_win
+      local height = vim.api.nvim_win_get_height(win_id)
+
+      local filename = entry.filename
+      local lnum = entry.lnum or 0
+
+      local context = math.floor(height / 2)
+      local start = math.max(0, lnum - context)
+      local finish = lnum + context
+
+      return maker(filename, lnum, start, finish)
+    end,
+  }
+end, {})
+
+previewers.qflist = defaulter(function(opts)
+  opts = opts or {}
+
+  local maker = get_maker(opts)
+
+  return previewers.new_termopen_previewer {
+    get_command = function(entry, status)
+      local win_id = status.preview_win
+      local height = vim.api.nvim_win_get_height(win_id)
+
+      local filename = entry.filename
+      local lnum = entry.lnum
+
+      local start, finish
+      if entry.start and entry.finish then
+        start = entry.start
+        finish = entry.finish
+      else
+        local context = math.floor(height / 2)
+        start = math.max(0, lnum - context)
+        finish = lnum + context
+      end
+
+      return maker(filename, lnum, start, finish)
+    end
+  }
+end, {})
+
+return previewers

lua/telescope/previewers/utils.lua

@@ -0,0 +1,17 @@
+local context_manager = require('plenary.context_manager')
+
+local utils = {}
+
+utils.with_preview_window = function(status, bufnr, callable)
+  if bufnr and vim.api.nvim_buf_call and false then
+    vim.api.nvim_buf_call(bufnr, callable)
+  else
+    return context_manager.with(function()
+      vim.cmd(string.format("noautocmd call nvim_set_current_win(%s)", status.preview_win))
+      coroutine.yield()
+      vim.cmd(string.format("noautocmd call nvim_set_current_win(%s)", status.prompt_win))
+    end, callable)
+  end
+end
+
+return utils