fix(api): avoid side effects with nvim_parse_cmd (#19890)

Save and restore the cursor and last search pattern and do not change
search history.

2 files changed, 74 insertions, 16 deletions

diff --git a/src/nvim/ex_docmd.c b/src/nvim/ex_docmd.c
index 3b1b6e81e3..5e8c7dbdda 100644
--- a/src/nvim/ex_docmd.c
+++ b/src/nvim/ex_docmd.c
@@ -1361,6 +1361,13 @@ bool is_cmd_ni(cmdidx_T cmdidx)
 bool parse_cmdline(char *cmdline, exarg_T *eap, CmdParseInfo *cmdinfo, char **errormsg)
 {
   char *after_modifier = NULL;
+  bool retval = false;
+  // parsing the command modifiers may set ex_pressedreturn
+  const bool save_ex_pressedreturn = ex_pressedreturn;
+  // parsing the command range may require moving the cursor
+  const pos_T save_cursor = curwin->w_cursor;
+  // parsing the command range may set the last search pattern
+  save_last_search_pattern();
 
   // Initialize cmdinfo
   CLEAR_POINTER(cmdinfo);
@@ -1375,13 +1382,10 @@ bool parse_cmdline(char *cmdline, exarg_T *eap, CmdParseInfo *cmdinfo, char **er
     .cookie = NULL,
   };
 
-  const bool save_ex_pressedreturn = ex_pressedreturn;
   // Parse command modifiers
   if (parse_command_modifiers(eap, errormsg, &cmdinfo->cmdmod, false) == FAIL) {
-    ex_pressedreturn = save_ex_pressedreturn;
-    goto err;
+    goto end;
   }
-  ex_pressedreturn = save_ex_pressedreturn;
   after_modifier = eap->cmd;
 
   // Save location after command modifiers
@@ -1394,21 +1398,21 @@ bool parse_cmdline(char *cmdline, exarg_T *eap, CmdParseInfo *cmdinfo, char **er
   char *p = find_ex_command(eap, NULL);
   if (p == NULL) {
     *errormsg = _(e_ambiguous_use_of_user_defined_command);
-    goto err;
+    goto end;
   }
 
   // Set command address type and parse command range
   set_cmd_addr_type(eap, p);
   eap->cmd = cmd;
-  if (parse_cmd_address(eap, errormsg, false) == FAIL) {
-    goto err;
+  if (parse_cmd_address(eap, errormsg, true) == FAIL) {
+    goto end;
   }
 
   // Skip colon and whitespace
   eap->cmd = skip_colon_white(eap->cmd, true);
   // Fail if command is a comment or if command doesn't exist
   if (*eap->cmd == NUL || *eap->cmd == '"') {
-    goto err;
+    goto end;
   }
   // Fail if command is invalid
   if (eap->cmdidx == CMD_SIZE) {
@@ -1417,7 +1421,7 @@ bool parse_cmdline(char *cmdline, exarg_T *eap, CmdParseInfo *cmdinfo, char **er
     char *cmdname = after_modifier ? after_modifier : cmdline;
     append_command(cmdname);
     *errormsg = (char *)IObuff;
-    goto err;
+    goto end;
   }
 
   // Correctly set 'forceit' for commands
@@ -1456,12 +1460,12 @@ bool parse_cmdline(char *cmdline, exarg_T *eap, CmdParseInfo *cmdinfo, char **er
   // Fail if command doesn't support bang but is used with a bang
   if (!(eap->argt & EX_BANG) && eap->forceit) {
     *errormsg = _(e_nobang);
-    goto err;
+    goto end;
   }
   // Fail if command doesn't support a range but it is given a range
   if (!(eap->argt & EX_RANGE) && eap->addr_count > 0) {
     *errormsg = _(e_norange);
-    goto err;
+    goto end;
   }
   // Set default range for command if required
   if ((eap->argt & EX_DFLALL) && eap->addr_count == 0) {
@@ -1471,7 +1475,7 @@ bool parse_cmdline(char *cmdline, exarg_T *eap, CmdParseInfo *cmdinfo, char **er
   // Parse register and count
   parse_register(eap);
   if (parse_count(eap, errormsg, false) == FAIL) {
-    goto err;
+    goto end;
   }
 
   // Remove leading whitespace and colon from next command
@@ -1487,10 +1491,15 @@ bool parse_cmdline(char *cmdline, exarg_T *eap, CmdParseInfo *cmdinfo, char **er
     cmdinfo->magic.bar = true;
   }
 
-  return true;
-err:
-  undo_cmdmod(&cmdinfo->cmdmod);
-  return false;
+  retval = true;
+end:
+  if (!retval) {
+    undo_cmdmod(&cmdinfo->cmdmod);
+  }
+  ex_pressedreturn = save_ex_pressedreturn;
+  curwin->w_cursor = save_cursor;
+  restore_last_search_pattern();
+  return retval;
 }
 
 static int execute_cmd0(int *retv, exarg_T *eap, char **errormsg, bool preview)
diff --git a/test/functional/api/vim_spec.lua b/test/functional/api/vim_spec.lua
index 72a03c409a..24d0b6da45 100644
--- a/test/functional/api/vim_spec.lua
+++ b/test/functional/api/vim_spec.lua
@@ -3668,6 +3668,55 @@ describe('API', function()
         :^                                                           |
       ]])
     end)
+    it('does not move cursor or change search history/pattern #19878 #19890', function()
+      meths.buf_set_lines(0, 0, -1, true, {'foo', 'bar', 'foo', 'bar'})
+      eq({1, 0}, meths.win_get_cursor(0))
+      eq('', funcs.getreg('/'))
+      eq('', funcs.histget('search'))
+      feed(':')  -- call the API in cmdline mode to test whether it changes search history
+      eq({
+        cmd = 'normal',
+        args = {'x'},
+        bang = true,
+        range = {3, 4},
+        count = -1,
+        reg = '',
+        addr = 'line',
+        magic = {
+          file = false,
+          bar = false,
+        },
+        nargs = '+',
+        nextcmd = '',
+        mods = {
+          browse = false,
+          confirm = false,
+          emsg_silent = false,
+          filter = {
+            pattern = "",
+            force = false,
+          },
+          hide = false,
+          keepalt = false,
+          keepjumps = false,
+          keepmarks = false,
+          keeppatterns = false,
+          lockmarks = false,
+          noautocmd = false,
+          noswapfile = false,
+          sandbox = false,
+          silent = false,
+          split = "",
+          tab = 0,
+          unsilent = false,
+          verbose = -1,
+          vertical = false,
+        }
+      }, meths.parse_cmd('+2;/bar/normal! x', {}))
+      eq({1, 0}, meths.win_get_cursor(0))
+      eq('', funcs.getreg('/'))
+      eq('', funcs.histget('search'))
+    end)
   end)
   describe('nvim_cmd', function()
     it('works', function ()