fix(lua): avoid internal error when :luado deletes lines (#27262)

src/nvim/lua/executor.c

@@ -1732,10 +1732,15 @@ void ex_luado(exarg_T *const eap)
     nlua_error(lstate, _("E5110: Error executing lua: %.*s"));
     return;
   }
+
+  buf_T *const was_curbuf = curbuf;
+
   for (linenr_T l = eap->line1; l <= eap->line2; l++) {
+    // Check the line number, the command may have deleted lines.
     if (l > curbuf->b_ml.ml_line_count) {
       break;
     }
+
     lua_pushvalue(lstate, -1);
     const char *const old_line = ml_get_buf(curbuf, l);
     // Get length of old_line here as calling Lua code may free it.
@@ -1746,6 +1751,13 @@ void ex_luado(exarg_T *const eap)
       nlua_error(lstate, _("E5111: Error calling lua: %.*s"));
       break;
     }
+
+    // Catch the command switching to another buffer.
+    // Check the line number, the command may have deleted lines.
+    if (curbuf != was_curbuf || l > curbuf->b_ml.ml_line_count) {
+      break;
+    }
+
     if (lua_isstring(lstate, -1)) {
       size_t new_line_len;
       const char *const new_line = lua_tolstring(lstate, -1, &new_line_len);
@@ -1760,6 +1772,7 @@ void ex_luado(exarg_T *const eap)
     }
     lua_pop(lstate, 1);
   }
+
   lua_pop(lstate, 1);
   check_cursor();
   redraw_curbuf_later(UPD_NOT_VALID);

test/functional/lua/commands_spec.lua

@@ -247,20 +247,30 @@ describe(':luado command', function()
     eq('', exec_capture('luado return ("<%02x>"):format(line:byte())'))
     eq({ '<31>', '<32>', '<33>' }, api.nvim_buf_get_lines(0, 0, -1, false))
   end)
+
   it('stops processing lines when suddenly out of lines', function()
     api.nvim_buf_set_lines(0, 0, 1, false, { 'ABC', 'def', 'gHi' })
     eq('', exec_capture('2,$luado runs = ((runs or 0) + 1) vim.api.nvim_command("%d")'))
     eq({ '' }, api.nvim_buf_get_lines(0, 0, -1, false))
     eq(1, fn.luaeval('runs'))
-  end)
+
-  it('works correctly when changing lines out of range', function()
+    api.nvim_buf_set_lines(0, 0, -1, false, { 'one', 'two', 'three' })
-    api.nvim_buf_set_lines(0, 0, 1, false, { 'ABC', 'def', 'gHi' })
+    eq('', exec_capture('luado vim.api.nvim_command("%d")'))
-    eq(
-      'Vim(luado):E322: Line number out of range: 1 past the end',
-      pcall_err(command, '2,$luado vim.api.nvim_command("%d") return linenr')
-    )
     eq({ '' }, api.nvim_buf_get_lines(0, 0, -1, false))
+
+    api.nvim_buf_set_lines(0, 0, -1, false, { 'one', 'two', 'three' })
+    eq('', exec_capture('luado vim.api.nvim_command("1,2d")'))
+    eq({ 'three' }, api.nvim_buf_get_lines(0, 0, -1, false))
+
+    api.nvim_buf_set_lines(0, 0, -1, false, { 'one', 'two', 'three' })
+    eq('', exec_capture('luado vim.api.nvim_command("2,3d"); return "REPLACED"'))
+    eq({ 'REPLACED' }, api.nvim_buf_get_lines(0, 0, -1, false))
+
+    api.nvim_buf_set_lines(0, 0, -1, false, { 'one', 'two', 'three' })
+    eq('', exec_capture('2,3luado vim.api.nvim_command("1,2d"); return "REPLACED"'))
+    eq({ 'three' }, api.nvim_buf_get_lines(0, 0, -1, false))
   end)
+
   it('fails on errors', function()
     eq(
       [[Vim(luado):E5109: Error loading lua: [string ":luado"]:0: unexpected symbol near ')']],
@@ -271,9 +281,11 @@ describe(':luado command', function()
       pcall_err(command, 'luado return liness + 1')
     )
   end)
+
   it('works with NULL errors', function()
     eq([=[Vim(luado):E5111: Error calling lua: [NULL]]=], exc_exec('luado error(nil)'))
   end)
+
   it('fails in sandbox when needed', function()
     api.nvim_buf_set_lines(0, 0, 1, false, { 'ABC', 'def', 'gHi' })
     eq(
@@ -282,6 +294,7 @@ describe(':luado command', function()
     )
     eq(NIL, fn.luaeval('runs'))
   end)
+
   it('works with long strings', function()
     local s = ('x'):rep(100500)
 
@@ -332,6 +345,7 @@ describe(':luafile', function()
       remove_trace(exc_exec('luafile ' .. fname))
     )
   end)
+
   it('works with NULL errors', function()
     write_file(fname, 'error(nil)')
     eq(