fix(api): nvim_parse_cmd error message in pcall() #23297

Problem:
nvim_parse_cmd() in pcall() may show an error message (side-effect):

    :lua pcall(vim.api.nvim_parse_cmd, vim.fn.getcmdline(), {})
    E16: Invalid range

Solution:
Avoid emsg() in the nvim_parse_cmd() codepath.

- refactor(api): add error message output parameter to get_address()
- fix: null check emsg() parameter
- refactor: remove emsg_off workaround from do_incsearch_highlighting()
- refactor: remove emsg_off workaround from cmdpreview_may_show()
- refactor: remove remaining calls to emsg() from parse_cmd_address() and get_address()
- (refactor): lint set_cmd_dflall_range()
- refactor: addr_error() - move output parameter to return value

Fix #20339

TODO:

These are the functions called by `get_address()`:

```
nvim_parse_cmd() -> parse_cmdline() -> parse_cmd_address() -> get_address()
    skipwhite()
    addr_error()
    qf_get_cur_idx()
    qf_get_cur_valid_idx()
    qf_get_size()
    qf_get_valid_size()
    mark_get()
    mark_check()
    assert()
    skip_regexp()
    magic_isset()
>   do_search()
>   searchit()
    ascii_isdigit()
    getdigits()
    getdigits_int32()
    compute_buffer_local_count()
    hasFolding()
```

From these functions, I found at least two that call emsg directly:
- do_search()
  - seems to be simple to refactor
- searchit()
  - will be more challenging because it may generate multiple error messages,
    which can't be handled by the current `errormsg` out-parameter.
    For example, it makes multiple calls to `vim_regexec_multi()` in a loop that
    possibly generate error messages, and later `searchit()` itself may generate
    another one:
    - https://github.com/neovim/neovim/blob/c194acbfc479d8e5839fa629363f93f6550d035c/src/nvim/search.c#L631-L647
    - https://github.com/neovim/neovim/blob/c194acbfc479d8e5839fa629363f93f6550d035c/src/nvim/search.c#L939-L954

---------

Co-authored-by: Justin M. Keyes <justinkz@gmail.com>

1 files changed, 19 insertions, 10 deletions

diff --git a/src/nvim/mark.c b/src/nvim/mark.c
index b3f94a42fc..c67dbb0b52 100644
--- a/src/nvim/mark.c
+++ b/src/nvim/mark.c
@@ -541,7 +541,11 @@ MarkMoveRes mark_move_to(fmark_T *fm, MarkMove flags)
 {
   static fmark_T fm_copy = INIT_FMARK;
   MarkMoveRes res = kMarkMoveSuccess;
-  if (!mark_check(fm)) {
+  const char *errormsg = NULL;
+  if (!mark_check(fm, &errormsg)) {
+    if (errormsg != NULL) {
+      emsg(errormsg);
+    }
     res = kMarkMoveFailed;
     goto end;
   }
@@ -557,7 +561,10 @@ MarkMoveRes mark_move_to(fmark_T *fm, MarkMove flags)
       goto end;
     }
     // Check line count now that the **destination buffer is loaded**.
-    if (!mark_check_line_bounds(curbuf, fm)) {
+    if (!mark_check_line_bounds(curbuf, fm, &errormsg)) {
+      if (errormsg != NULL) {
+        emsg(errormsg);
+      }
       res |= kMarkMoveFailed;
       goto end;
     }
@@ -710,43 +717,45 @@ static void fmarks_check_one(xfmark_T *fm, char *name, buf_T *buf)
 
 /// Check the position in @a fm is valid.
 ///
-/// Emit error message and return accordingly.
-///
 /// Checks for:
 /// - NULL raising unknown mark error.
 /// - Line number <= 0 raising mark not set.
 /// - Line number > buffer line count, raising invalid mark.
+///
 /// @param fm[in]  File mark to check.
+/// @param errormsg[out]  Error message, if any.
 ///
 /// @return  true if the mark passes all the above checks, else false.
-bool mark_check(fmark_T *fm)
+bool mark_check(fmark_T *fm, const char **errormsg)
 {
   if (fm == NULL) {
-    emsg(_(e_umark));
+    *errormsg = _(e_umark);
     return false;
   } else if (fm->mark.lnum <= 0) {
     // In both cases it's an error but only raise when equals to 0
     if (fm->mark.lnum == 0) {
-      emsg(_(e_marknotset));
+      *errormsg = _(e_marknotset);
     }
     return false;
   }
   // Only check for valid line number if the buffer is loaded.
-  if (fm->fnum == curbuf->handle && !mark_check_line_bounds(curbuf, fm)) {
+  if (fm->fnum == curbuf->handle && !mark_check_line_bounds(curbuf, fm, errormsg)) {
     return false;
   }
   return true;
 }
 
 /// Check if a mark line number is greater than the buffer line count, and set e_markinval.
+///
 /// @note  Should be done after the buffer is loaded into memory.
 /// @param buf  Buffer where the mark is set.
 /// @param fm  Mark to check.
+/// @param errormsg[out]  Error message, if any.
 /// @return  true if below line count else false.
-bool mark_check_line_bounds(buf_T *buf, fmark_T *fm)
+bool mark_check_line_bounds(buf_T *buf, fmark_T *fm, const char **errormsg)
 {
   if (buf != NULL && fm->mark.lnum > buf->b_ml.ml_line_count) {
-    emsg(_(e_markinval));
+    *errormsg = _(e_markinval);
     return false;
   }
   return true;