fix(terminal): wrong scrollback with BufFile* autocommand (#37601)

Problem:  Wrong terminal scrollback if BufFile* autocommand drains PTY
          output but doesn't process the pending refresh.
Solution: Refresh scrollback before refreshing screen in terminal_open()
          if scrollback has been allocated.

src/nvim/terminal.c

@@ -563,6 +563,11 @@ void terminal_open(Terminal **termpp, buf_T *buf)
   aco_save_T aco;
   aucmd_prepbuf(&aco, buf);
 
+  if (term->sb_buffer != NULL) {
+    // If scrollback has been allocated by autocommands between terminal_alloc()
+    // and terminal_open(), it also needs to be refreshed.
+    refresh_scrollback(term, buf);
+  }
   refresh_screen(term, buf);
   set_option_value(kOptBuftype, STATIC_CSTR_AS_OPTVAL("terminal"), OPT_LOCAL);
 

test/functional/terminal/buffer_spec.lua

@@ -773,40 +773,56 @@ describe(':terminal buffer', function()
   end)
 
   --- @param subcmd 'REP'|'REPFAST'
-  local function check_term_rep_20000(subcmd)
+  local function check_term_rep(subcmd, count)
     local screen = Screen.new(50, 7)
-    api.nvim_set_option_value('scrollback', 30000, {})
     api.nvim_create_autocmd('TermClose', { command = 'let g:did_termclose = 1' })
-    fn.jobstart({ testprg('shell-test'), subcmd, '20000', 'TEST' }, { term = true })
+    fn.jobstart({ testprg('shell-test'), subcmd, count, 'TEST' }, { term = true })
     retry(nil, nil, function()
       eq(1, api.nvim_get_var('did_termclose'))
     end)
     feed('i')
-    screen:expect([[
+    screen:expect(([[
-      19996: TEST                                       |
+      %d: TEST{MATCH: +}|
-      19997: TEST                                       |
+      %d: TEST{MATCH: +}|
-      19998: TEST                                       |
+      %d: TEST{MATCH: +}|
-      19999: TEST                                       |
+      %d: TEST{MATCH: +}|
                                                         |
       [Process exited 0]^                                |
       {5:-- TERMINAL --}                                    |
-    ]])
+    ]]):format(count - 4, count - 3, count - 2, count - 1))
     local lines = api.nvim_buf_get_lines(0, 0, -1, true)
-    for i = 0, 19999 do
+    for i = 1, count do
-      eq(('%d: TEST'):format(i), lines[i + 1])
+      eq(('%d: TEST'):format(i - 1), lines[i])
     end
   end
 
   it('does not drop data when job exits immediately after output #3030', function()
-    check_term_rep_20000('REPFAST')
+    api.nvim_set_option_value('scrollback', 30000, {})
+    check_term_rep('REPFAST', 20000)
   end)
 
   it('does not drop data when autocommands poll for events #37559', function()
+    api.nvim_set_option_value('scrollback', 30000, {})
     api.nvim_create_autocmd('BufFilePre', { command = 'sleep 50m', nested = true })
     api.nvim_create_autocmd('BufFilePost', { command = 'sleep 50m', nested = true })
     api.nvim_create_autocmd('TermOpen', { command = 'sleep 50m', nested = true })
     -- REP pauses 1 ms every 100 lines, so each autocommand processes some output.
-    check_term_rep_20000('REP')
+    check_term_rep('REP', 20000)
+  end)
+
+  describe('scrollback is correct if all output is drained by', function()
+    for _, event in ipairs({ 'BufFilePre', 'BufFilePost', 'TermOpen' }) do
+      describe(('%s autocommand that lasts for'):format(event), function()
+        for _, delay in ipairs({ 5, 15, 25 }) do
+          -- Terminal refresh delay is 10 ms.
+          it(('%.1f * terminal refresh delay'):format(delay / 10), function()
+            local cmd = ('sleep %dm'):format(delay)
+            api.nvim_create_autocmd(event, { command = cmd, nested = true })
+            check_term_rep('REPFAST', 200)
+          end)
+        end
+      end)
+    end
   end)
 
   it('handles unprintable chars', function()

test/functional/terminal/channel_spec.lua

@@ -160,14 +160,21 @@ local function test_autocmd_no_crash(event, extra_tests)
     ]])
   end)
 
+  local input_prompt_screen = [[
+                                                                |
+    {1:~                                                           }|*2
+    ^                                                            |
+  ]]
+  local oldbuf_screen = [[
+    ^OLDBUF                                                      |
+    {1:~                                                           }|*2
+                                                                |
+  ]]
+
   it('processes job exit event when using jobstart(…,{term=true})', function()
     api.nvim_create_autocmd(event, { command = "call input('')" })
     async_meths.nvim_call_function('jobstart', { term_args, { term = true } })
-    env.screen:expect([[
+    env.screen:expect(input_prompt_screen)
-                                                                  |
-      {1:~                                                           }|*2
-      ^                                                            |
-    ]])
     vim.uv.sleep(20)
     feed('<CR>')
     env.screen:expect([[
@@ -184,29 +191,40 @@ local function test_autocmd_no_crash(event, extra_tests)
       {5:-- TERMINAL --}                                              |
     ]])
     feed('<CR>')
-    env.screen:expect([[
+    env.screen:expect(oldbuf_screen)
-      ^OLDBUF                                                      |
-      {1:~                                                           }|*2
-                                                                  |
-    ]])
     assert_alive()
   end)
 
   it('wipes buffer and processes events when using jobstart(…,{term=true})', function()
     api.nvim_create_autocmd(event, { command = "call Wipe() | call input('')" })
     async_meths.nvim_call_function('jobstart', { term_args, { term = true } })
-    env.screen:expect([[
+    env.screen:expect(input_prompt_screen)
-                                                                  |
-      {1:~                                                           }|*2
-      ^                                                            |
-    ]])
     vim.uv.sleep(20)
     feed('<CR>')
-    env.screen:expect([[
+    env.screen:expect(oldbuf_screen)
-      ^OLDBUF                                                      |
+    assert_alive()
-      {1:~                                                           }|*2
+    eq('Xoldbuf', eval('bufname()'))
-                                                                  |
+    eq(0, eval([[exists('b:term_title')]]))
-    ]])
+  end)
+
+  it('processes :bwipe from TermClose when using jobstart(…,{term=true})', function()
+    local term_buf = api.nvim_get_current_buf()
+    api.nvim_create_autocmd('TermClose', { command = ('bwipe! %d'):format(term_buf) })
+    api.nvim_create_autocmd(event, { command = "call input('')", nested = true })
+    async_meths.nvim_call_function('jobstart', { term_args, { term = true } })
+    env.screen:expect(input_prompt_screen)
+    vim.uv.sleep(20)
+    feed('<CR>')
+    env.screen:expect(oldbuf_screen)
+    assert_alive()
+    eq('Xoldbuf', eval('bufname()'))
+    eq(0, eval([[exists('b:term_title')]]))
+  end)
+
+  it('only wipes buffer when using jobstart(…,{term=true})', function()
+    api.nvim_create_autocmd(event, { command = 'call Wipe()' })
+    async_meths.nvim_call_function('jobstart', { term_args, { term = true } })
+    env.screen:expect(oldbuf_screen)
     assert_alive()
     eq('Xoldbuf', eval('bufname()'))
     eq(0, eval([[exists('b:term_title')]]))