fix(picker): better handling of buffers with custom URIs. Fixes #677

lua/snacks/picker/preview.lua

@@ -60,10 +60,16 @@ end
 
 ---@param ctx snacks.picker.preview.ctx
 function M.file(ctx)
-  if ctx.item.buf and not vim.api.nvim_buf_is_valid(ctx.item.buf) then
+  if ctx.item.buf and not ctx.item.file and not vim.api.nvim_buf_is_valid(ctx.item.buf) then
     ctx.preview:notify("Buffer no longer exists", "error")
     return
   end
+
+  -- used by some LSP servers that load buffers with custom URIs
+  if ctx.item.buf and vim.uri_from_bufnr(ctx.item.buf):sub(1, 4) ~= "file" then
+    vim.fn.bufload(ctx.item.buf)
+  end
+
   if ctx.item.buf and vim.api.nvim_buf_is_loaded(ctx.item.buf) then
     local name = vim.api.nvim_buf_get_name(ctx.item.buf)
     name = uv.fs_stat(name) and vim.fn.fnamemodify(name, ":t") or name

lua/snacks/picker/util/init.lua

@@ -1,6 +1,8 @@
 ---@class snacks.picker.util
 local M = {}
 
+local uv = vim.uv or vim.loop
+
 ---@param item snacks.picker.Item
 function M.path(item)
   if not (item and item.file) then
@@ -191,6 +193,36 @@ function M.resolve(item)
   return item
 end
 
+--- Reads the lines of a file.
+--- This is about 8x faster than `vim.fn.readfile`
+--- and 3x faster than `io.lines` using a
+--- test files of 225KB and 8300 lines.
+---@param file string
+function M.lines(file)
+  local fd = uv.fs_open(file, "r", 438)
+  if not fd then
+    return {}
+  end
+  local stat = assert(uv.fs_fstat(fd))
+  local data = assert(uv.fs_read(fd, stat.size, 0))
+  uv.fs_close(fd)
+
+  local lines, from = {}, 1 --- @type string[], number
+  while from <= #data do
+    local nl = data:find("\n", from, true)
+    if nl then
+      local cr = data:byte(nl - 1, nl - 1) == 13 -- \r
+      local line = data:sub(from, nl - (cr and 2 or 1))
+      lines[#lines + 1] = line
+      from = nl + 1
+    else
+      lines[#lines + 1] = data:sub(from)
+      break
+    end
+  end
+  return lines
+end
+
 ---@param s string
 ---@param index number
 ---@param encoding string
@@ -210,13 +242,21 @@ function M.resolve_loc(item, buf)
   if not item or not item.loc or item.loc.resolved then
     return item
   end
-  -- return vim._str_byteindex(s, index, encoding == 'utf-16')
 
   local lines = {} ---@type string[]
-  if buf and vim.api.nvim_buf_is_valid(buf) then
+  if item.buf and vim.api.nvim_buf_is_loaded(item.buf) then
+    -- valid and loaded buffer
+    lines = vim.api.nvim_buf_get_lines(item.buf, 0, -1, false)
+  elseif item.buf and vim.uri_from_bufnr(item.buf):sub(1, 4) ~= "file" then
+    -- item buffer with a custom uri
+    vim.fn.bufload(item.buf)
+    lines = vim.api.nvim_buf_get_lines(item.buf, 0, -1, false)
+  elseif buf and vim.api.nvim_buf_is_valid(buf) then
+    -- custom buffer (typically for preview)
     lines = vim.api.nvim_buf_get_lines(buf, 0, -1, false)
-  else
-    lines = vim.fn.readfile(item.file)
+  elseif item.file then
+    -- last resort, read the file
+    lines = M.lines(item.file)
   end
 
   ---@param pos lsp.Position?