fix(terminal): do not trim whitespace that is actually in the terminal (#16423)

src/nvim/terminal.c

@@ -1374,26 +1374,21 @@ static void fetch_row(Terminal *term, int row, int end_col)
   while (col < end_col) {
     VTermScreenCell cell;
     fetch_cell(term, row, col, &cell);
-    int cell_len = 0;
     if (cell.chars[0]) {
+      int cell_len = 0;
       for (int i = 0; cell.chars[i]; i++) {
         cell_len += utf_char2bytes((int)cell.chars[i], ptr + cell_len);
       }
-    } else {
-      *ptr = ' ';
-      cell_len = 1;
-    }
-    char c = *ptr;
       ptr += cell_len;
-    if (c != ' ') {
-      // only increase the line length if the last character is not whitespace
       line_len = (size_t)(ptr - term->textbuf);
+    } else {
+      *ptr++ = ' ';
     }
     col += cell.width;
   }
 
-  // trim trailing whitespace
+  // end of line
-  term->textbuf[line_len] = 0;
+  term->textbuf[line_len] = NUL;
 }
 
 static bool fetch_cell(Terminal *term, int row, int col, VTermScreenCell *cell)

test/functional/api/buffer_updates_spec.lua

@@ -785,7 +785,8 @@ describe('API: buffer events:', function()
 
   local function lines_subset(first, second)
     for i = 1,#first do
-      if first[i] ~= second[i] then
+      -- need to ignore trailing spaces
+      if first[i]:gsub(' +$', '') ~= second[i]:gsub(' +$', '') then
         return false
       end
     end

test/functional/core/startup_spec.lua

@@ -496,12 +496,13 @@ describe('sysinit', function()
   it('fixed hang issue with -D (#12647)', function()
     if helpers.pending_win32(pending) then return end
     local screen
-    screen = Screen.new(60, 6)
+    screen = Screen.new(60, 7)
     screen:attach()
     command([[let g:id = termopen('"]]..nvim_prog..
     [[" -u NONE -i NONE --cmd "set noruler" -D')]])
     screen:expect([[
       ^                                                            |
+                                                                  |
       Entering Debug mode.  Type "cont" to continue.              |
       cmd: augroup nvim_terminal                                  |
       >                                                           |
@@ -512,6 +513,7 @@ describe('sysinit', function()
     screen:expect([[
       ^                                                            |
       ~                                                           |
+      ~                                                           |
       [No Name]                                                   |
                                                                   |
       <" -u NONE -i NONE --cmd "set noruler" -D 1,0-1          All|

test/functional/terminal/cursor_spec.lua

@@ -5,6 +5,7 @@ local feed, clear, nvim = helpers.feed, helpers.clear, helpers.nvim
 local nvim_dir, command = helpers.nvim_dir, helpers.command
 local nvim_prog = helpers.nvim_prog
 local eq, eval = helpers.eq, helpers.eval
+local matches = helpers.matches
 local feed_command = helpers.feed_command
 local hide_cursor = thelpers.hide_cursor
 local show_cursor = thelpers.show_cursor
@@ -177,7 +178,6 @@ describe('cursor with customized highlighting', function()
 end)
 
 describe('buffer cursor position is correct in terminal without number column', function()
-  if helpers.pending_win32(pending) then return end
   local screen
 
   local function setup_ex_register(str)
@@ -525,10 +525,36 @@ describe('buffer cursor position is correct in terminal without number column',
       eq({6, 1}, eval('nvim_win_get_cursor(0)'))
     end)
   end)
+
+  it('at the end of a line with trailing spaces #16234', function()
+    setup_ex_register('aaaaaaaa    ')
+    feed('<C-R>r')
+    screen:expect([[
+                                                                            |
+                                                                            |
+                                                                            |
+                                                                            |
+      Entering Ex mode.  Type "visual" to go to Normal mode.                |
+      :aaaaaaaa    {1: }                                                        |
+      {3:-- TERMINAL --}                                                        |
+    ]])
+    matches('^:aaaaaaaa    ', eval('nvim_get_current_line()'))
+    eq({6, 13}, eval('nvim_win_get_cursor(0)'))
+    feed([[<C-\><C-N>]])
+    screen:expect([[
+                                                                            |
+                                                                            |
+                                                                            |
+                                                                            |
+      Entering Ex mode.  Type "visual" to go to Normal mode.                |
+      :aaaaaaaa   ^ {2: }                                                        |
+                                                                            |
+    ]])
+    eq({6, 12}, eval('nvim_win_get_cursor(0)'))
+  end)
 end)
 
 describe('buffer cursor position is correct in terminal with number column', function()
-  if helpers.pending_win32(pending) then return end
   local screen
 
   local function setup_ex_register(str)
@@ -879,4 +905,31 @@ describe('buffer cursor position is correct in terminal with number column', fun
       eq({6, 1}, eval('nvim_win_get_cursor(0)'))
     end)
   end)
+
+  it('at the end of a line with trailing spaces #16234', function()
+    setup_ex_register('aaaaaaaa    ')
+    feed('<C-R>r')
+    screen:expect([[
+      {7:  1 }                                                                  |
+      {7:  2 }                                                                  |
+      {7:  3 }                                                                  |
+      {7:  4 }                                                                  |
+      {7:  5 }Entering Ex mode.  Type "visual" to go to Normal mode.            |
+      {7:  6 }:aaaaaaaa    {1: }                                                    |
+      {3:-- TERMINAL --}                                                        |
+    ]])
+    matches('^:aaaaaaaa    ', eval('nvim_get_current_line()'))
+    eq({6, 13}, eval('nvim_win_get_cursor(0)'))
+    feed([[<C-\><C-N>]])
+    screen:expect([[
+      {7:  1 }                                                                  |
+      {7:  2 }                                                                  |
+      {7:  3 }                                                                  |
+      {7:  4 }                                                                  |
+      {7:  5 }Entering Ex mode.  Type "visual" to go to Normal mode.            |
+      {7:  6 }:aaaaaaaa   ^ {2: }                                                    |
+                                                                            |
+    ]])
+    eq({6, 12}, eval('nvim_win_get_cursor(0)'))
+  end)
 end)