feat(fzf_lua): add custom ActionPreviewer for improved action preview

lua/codecompanion/providers/actions/fzf_lua.lua

@@ -1,6 +1,87 @@
 local config = require("codecompanion.config")
 local fzf = require("fzf-lua")
 
+---A custom fzf-lua previewer for the Action Palette
+---@class CodeCompanion.Actions.FzfLua.ActionPreviewer: fzf-lua.previewer.Builtin
+---@field name_to_item table<string, CodeCompanion.ActionItem>
+local ActionPreviewer = require("fzf-lua.previewer.builtin").base:extend()
+
+---Initialize the previewer instance
+---@param o table? `previewer` table passed to `fzf_exec`
+---@param opts fzf-lua.config.Base
+function ActionPreviewer:new(o, opts)
+  ActionPreviewer.super.new(self, o, opts)
+  self.name_to_item = o.name_to_item
+end
+
+---Return enforced window options for the preview window
+---@return table
+function ActionPreviewer:gen_winopts()
+  local enforced_win_opts = {
+    wrap = true,
+    number = false,
+    relativenumber = false,
+    cursorcolumn = false,
+    spell = false,
+    list = false,
+    signcolumn = "no",
+    foldcolumn = "0",
+    colorcolumn = "",
+  }
+  return vim.tbl_extend("force", self.winopts, enforced_win_opts)
+end
+
+---Disable clearing preview between updates
+---@param _ any
+---@return boolean
+function ActionPreviewer:should_clear_preview(_)
+  return false
+end
+
+---Parse the selected entry string into the original action item
+---@param entry_str string
+---@return CodeCompanion.ActionItem|table
+function ActionPreviewer:parse_entry(entry_str)
+  if not entry_str or entry_str == "" then
+    return {}
+  end
+  return self.name_to_item[entry_str] or {}
+end
+
+---Render the preview buffer for the provided entry
+---@param entry_str string
+---@return nil
+function ActionPreviewer:populate_preview_buf(entry_str)
+  if not self.win or not self.win:validate_preview() then
+    return
+  end
+
+  local item = self:parse_entry(entry_str)
+  if not item or vim.tbl_isempty(item) then
+    return
+  end
+
+  -- Update preview title to the action's name if available
+  if item.name and type(item.name) == "string" and #item.name > 0 then
+    self.win:update_preview_title(" " .. item.name .. " ")
+  end
+
+  if item.description == "[No messages]" and item.bufnr and vim.api.nvim_buf_is_valid(item.bufnr) then
+    -- Attach the provided buffer directly
+    -- Protect user buffer from being deleted when the previewer closes
+    self.listed_buffers[tostring(item.bufnr)] = true
+    self:set_preview_buf(item.bufnr)
+    self:update_render_markdown()
+  else
+    local tmpbuf = self:get_tmp_buffer()
+    local description = item.description and vim.split(item.description, "\n", { plain = true }) or { "No description" }
+    vim.api.nvim_buf_set_lines(tmpbuf, 0, -1, false, description)
+    self:set_preview_buf(tmpbuf)
+  end
+
+  self.win:update_preview_scrollbar()
+end
+
 ---@class CodeCompanion.Actions.Provider.FZF: CodeCompanion.SlashCommand.Provider
 ---@field context table
 ---@field resolve function
@@ -11,33 +92,39 @@ function FZF.new(args)
   return setmetatable(args, { __index = FZF })
 end
 
----@param items table The items to display in the picker
+---@param items CodeCompanion.ActionItem[] The items to display in the picker
 ---@param opts? table The options for the picker
 ---@return nil
 function FZF:picker(items, opts)
   opts = opts or {}
   opts.prompt = opts.prompt or config.display.action_palette.opts.title or "CodeCompanion actions"
 
-  local item_names = {}
-  local name_to_item = {}
+  local names = vim.tbl_map(function(item)
+    return item.name
+  end, items)
 
+  local name_to_item = {}
   for _, item in ipairs(items) do
-    table.insert(item_names, item.name)
     name_to_item[item.name] = item
   end
 
-  fzf.fzf_exec(item_names, {
-    prompt = opts.prompt,
-    preview = {
-      fn = function(it)
-        return name_to_item[it[1]].description
+  fzf.fzf_exec(names, {
+    winopts = { title = " " .. opts.prompt .. " " },
+    previewer = {
+      _ctor = function()
+        return ActionPreviewer
       end,
+      name_to_item = name_to_item,
     },
     actions = {
       ["default"] = function(selected)
-        if selected or vim.tbl_count(selected) ~= 0 then
-          for _, selection in ipairs(selected) do
-            return require("codecompanion.providers.actions.shared").select(self, name_to_item[selection])
+        if not selected or #selected == 0 then
+          return
+        end
+        for _, selection in ipairs(selected) do
+          local item = name_to_item[selection]
+          if item then
+            return require("codecompanion.providers.actions.shared").select(self, item)
           end
         end
       end,

lua/codecompanion/providers/slash_commands/fzf_lua.lua

@@ -22,7 +22,7 @@ end
 ---@return table
 function FZF:display(transformer)
   return {
-    prompt = self.title,
+    winopts = { title = " " .. self.title .. " " },
     actions = {
       ["default"] = function(selected, opts)
         if selected or vim.tbl_count(selected) ~= 0 then

lua/codecompanion/types.lua

@@ -164,3 +164,29 @@
 ---@field validate table Validate an item
 ---@field resolve table Resolve an item into an action
 ---@field context table The buffer context
+
+---@class CodeCompanion.ActionOptions
+---@field index? number Ordering position for display
+---@field stop_context_insertion? boolean Prevents auto-added context on open
+---@field modes? string[] Optional list of modes where the action is visible (e.g. {"n","v"})
+---@field is_default? boolean Marks prompt as part of default library
+---@field user_prompt? boolean Ask user for additional input before executing
+---@field auto_submit? boolean Auto-submit the resulting prompt to the LLM
+---@field short_name? string Short alias used for command-line invocation
+
+---@class CodeCompanion.ActionPicker
+---@field prompt? string Optional prompt/title shown by providers
+---@field items table|fun(context: table): table Items to show or a function returning items
+---@field columns? any Optional provider-specific column config
+
+---@class CodeCompanion.ActionItem
+---@field name string Display name in the Action Palette
+---@field description? string Description or preview text
+---@field strategy? string Strategy to execute (e.g. "chat")
+---@field type? string Optional type hint used by some providers
+---@field opts? CodeCompanion.ActionOptions Additional behavior/config flags
+---@field prompts? table Optional initial prompts specification
+---@field picker? CodeCompanion.ActionPicker Optional nested picker spec
+---@field callback? fun(context: table): any Optional direct action callback
+---@field context? table Optional context forwarded to execution
+---@field bufnr? integer Optional buffer number for open chats preview