fix: store paths in g:BufferlinePositions (#780)

This fixes an issue where restoring the custom sort order from a saved session doesn't work correctly most of the time, because it stores buffer ids in g:BufferlinePositions which are not preserved by :mksession. The fix is to store the full paths of the buffers instead. vim.json is required to stringify the list as :mksession only stores string/number values.

lua/bufferline.lua

@@ -116,7 +116,7 @@ local function setup_autocommands(conf)
     api.nvim_create_autocmd("SessionLoadPost", {
       pattern = "*",
       group = BUFFERLINE_GROUP,
-      callback = function() state.restore_positions() end,
+      callback = function() state.custom_sort = utils.restore_positions() end,
     })
   end
   if not options.always_show_bufferline then

lua/bufferline/commands.lua

@@ -8,25 +8,13 @@ local utils = lazy.require("bufferline.utils") ---@module "bufferline.utils"
 local config = lazy.require("bufferline.config") ---@module "bufferline.config"
 local groups = lazy.require("bufferline.groups") ---@module "bufferline.groups"
 local sorters = lazy.require("bufferline.sorters") ---@module "bufferline.sorters"
-local constants = lazy.require("bufferline.constants") ---@module "bufferline.constants"
 local pick = lazy.require("bufferline.pick") ---@module "bufferline.pick"
 
 local M = {}
 
-local positions_key = constants.positions_key
-
 local fmt = string.format
 local api = vim.api
 
----@param ids number[]
-local function save_positions(ids) vim.g[positions_key] = table.concat(ids, ",") end
-
---- @param elements bufferline.TabElement[]
---- @return number[]
-local function get_ids(elements)
-  return vim.tbl_map(function(item) return item.id end, elements)
-end
-
 --- open the current element
 ---@param id number
 local function open_element(id)
@@ -170,9 +158,9 @@ function M.move_to(to_index, from_index)
     local destination_buf = state.components[next_index]
     state.components[next_index] = item
     state.components[index] = destination_buf
-    state.custom_sort = get_ids(state.components)
+    state.custom_sort = utils.get_ids(state.components)
     local opts = config.options
-    if opts.persist_buffer_sort then save_positions(state.custom_sort) end
+    if opts.persist_buffer_sort then utils.save_positions(state.custom_sort) end
     ui.refresh()
   end
 end
@@ -269,9 +257,9 @@ end
 function M.sort_by(sort_by)
   if next(state.components) == nil then return utils.notify("Unable to find elements to sort, sorry", "warn") end
   sorters.sort(state.components, { sort_by = sort_by })
-  state.custom_sort = get_ids(state.components)
+  state.custom_sort = utils.get_ids(state.components)
   local opts = config.options
-  if opts.persist_buffer_sort then save_positions(state.custom_sort) end
+  if opts.persist_buffer_sort then utils.save_positions(state.custom_sort) end
   ui.refresh()
 end
 

lua/bufferline/state.lua

@@ -1,7 +1,6 @@
 local M = {}
 
 local lazy = require("bufferline.lazy")
-local constants = lazy.require("bufferline.constants") ---@module "bufferline.constants"
 local utils = lazy.require("bufferline.utils") ---@module "bufferline.utils"
 
 -----------------------------------------------------------------------------//
@@ -21,15 +20,6 @@ local state = {
   right_offset_size = 0,
 }
 
-function M.restore_positions()
-  local str = vim.g[constants.positions_key]
-  if not str then return str end
-  -- these are converted to strings when stored
-  -- so have to be converted back before usage
-  local ids = vim.split(str, ",")
-  if ids and #ids > 0 then state.custom_sort = vim.tbl_map(tonumber, ids) end
-end
-
 ---@param list bufferline.Component[]
 ---@return bufferline.Component[]
 local function filter_invisible(list)

lua/bufferline/types.lua

@@ -216,7 +216,7 @@
 ---@field is_picking boolean
 ---@field visible_components bufferline.Component[]
 ---@field __components bufferline.Component[]
----@field custom_sort number[]
+---@field custom_sort number[]?
 ---@field left_offset_size number
 ---@field right_offset_size number
 

lua/bufferline/utils/init.lua

@@ -154,6 +154,30 @@ function M.notify(msg, level, opts)
   vim.schedule(function() vim.notify(msg, level, nopts) end)
 end
 
+---@return number[]?
+function M.restore_positions()
+  local str = vim.g[constants.positions_key]
+  local ok, paths = pcall(vim.json.decode, str)
+  if not ok or type(paths) ~= "table" or #paths == 0 then return nil end
+  local ids = vim.tbl_map(function(path)
+    local escaped = vim.fn.fnameescape(path)
+    return vim.fn.bufnr("^" .. escaped .. "$" --[[@as integer]])
+  end, paths)
+  return vim.tbl_filter(function(id) return id ~= -1 end, ids)
+end
+
+---@param ids number[]
+function M.save_positions(ids)
+  local paths = vim.tbl_map(function(id) return vim.api.nvim_buf_get_name(id) end, ids)
+  vim.g[constants.positions_key] = vim.json.encode(paths)
+end
+
+--- @param elements bufferline.TabElement[]
+--- @return number[]
+function M.get_ids(elements)
+  return vim.tbl_map(function(item) return item.id end, elements)
+end
+
 ---Get an icon for a filetype using either nvim-web-devicons or vim-devicons
 ---if using the lua plugin this also returns the icon's highlights
 ---@param opts bufferline.IconFetcherOpts

tests/utils_spec.lua

@@ -18,4 +18,51 @@ describe("Utils tests", function()
     local truncated = utils.truncate_name("filename.md.md", 13)
     assert.is_equal(truncated, "filename.md" .. constants.ELLIPSIS)
   end)
+
+  it("should save/restore positions correctly", function()
+    -- remove existing buffers
+    vim.cmd("silent %bwipeout!")
+
+    local names = { "c.txt", "a.txt", "d.txt", "e.txt", "b.txt" }
+    local bufs = {}
+    for _, name in ipairs(names) do
+      vim.cmd.edit(name)
+      bufs[name] = api.nvim_get_current_buf()
+    end
+
+    local ids = {
+      bufs["a.txt"],
+      bufs["b.txt"],
+      bufs["c.txt"],
+      bufs["d.txt"],
+      bufs["e.txt"],
+    }
+
+    utils.save_positions(ids)
+
+    assert.same(utils.restore_positions(), ids)
+
+    -- restore_positions should not return invalid bufids
+
+    vim.cmd("bwipeout! " .. bufs["c.txt"])
+
+    ids = {
+      bufs["a.txt"],
+      bufs["b.txt"],
+      bufs["d.txt"],
+      bufs["e.txt"],
+    }
+    assert.same(utils.restore_positions(), ids)
+
+    vim.g[constants.positions_key] = '["INVALID_PATH"]'
+    assert.same(utils.restore_positions(), {})
+
+    -- empty or invalid JSON should return nil
+
+    vim.g[constants.positions_key] = "[]"
+    assert.is_equal(utils.restore_positions(), nil)
+
+    vim.g[constants.positions_key] = ""
+    assert.is_equal(utils.restore_positions(), nil)
+  end)
 end)