fix(snippet): jumping backwards to choice node (#35062)

Avoid duplicate text when jumping back to a choice node. Set cursor to
end of tabstop range and prioritize current choice in completion items.

runtime/lua/vim/snippet.lua

@@ -257,10 +257,21 @@ local M = { session = nil }
 local function display_choices(tabstop)
   assert(tabstop.choices, 'Tabstop has no choices')
 
+  local text = tabstop:get_text()
+  local found_text = false
+
   local start_col = tabstop:get_range()[2] + 1
   local matches = {} --- @type table[]
   for _, choice in ipairs(tabstop.choices) do
-    matches[#matches + 1] = { word = choice }
+    if choice ~= text then
+      matches[#matches + 1] = { word = choice }
+    else
+      found_text = true
+    end
+  end
+
+  if found_text then
+    table.insert(matches, 1, text)
   end
 
   vim.defer_fn(function()
@@ -298,6 +309,7 @@ local function select_tabstop(tabstop)
       vim.cmd.startinsert({ bang = range[4] >= #vim.api.nvim_get_current_line() })
     end
     if tabstop.choices then
+      vim.fn.cursor(range[3] + 1, range[4] + 1)
       display_choices(tabstop)
     end
   else

test/functional/lua/snippet_spec.lua

@@ -240,6 +240,23 @@ describe('vim.snippet', function()
     eq({ 'public function foo() {', '\t', '}' }, buf_lines(0))
   end)
 
+  it('does not change the chosen text when jumping back to a choice tabstop', function()
+    test_expand_success(
+      { '${1|public,protected,private|} function ${2:name}() {', '\t$0', '}' },
+      { ' function name() {', '\t', '}' }
+    )
+    wait_for_pum()
+    feed('<C-n><C-y><Tab>')
+    poke_eventloop()
+    feed('<S-Tab>')
+    poke_eventloop()
+    wait_for_pum()
+    feed('<Tab>')
+    poke_eventloop()
+    feed('foo')
+    eq({ 'protected function foo() {', '\t', '}' }, buf_lines(0))
+  end)
+
   it('jumps through adjacent tabstops', function()
     test_expand_success(
       { 'for i=1,${1:to}${2:,step} do\n\t$3\nend' },