fix(api): generic error messages, not using TRY_WRAP #31596

Problem:
- API functions using `try_start` directly, do not surface the
  underlying error message, and instead show generic messages.
- Error-handling code is duplicated in the API impl.
- Failure modes are not tested.

Solution:
- Use `TRY_WRAP`.
- Add tests.

2 files changed, 5 insertions, 9 deletions

diff --git a/runtime/doc/api.txt b/runtime/doc/api.txt
index cb3b2a3f77..70fda5ce8a 100644
--- a/runtime/doc/api.txt
+++ b/runtime/doc/api.txt
@@ -1647,11 +1647,9 @@ nvim_command({command})                                       *nvim_command()*
 
     On execution error: fails with Vimscript error, updates v:errmsg.
 
-    Prefer using |nvim_cmd()| or |nvim_exec2()| over this. To evaluate
-    multiple lines of Vim script or an Ex command directly, use
-    |nvim_exec2()|. To construct an Ex command using a structured format and
-    then execute it, use |nvim_cmd()|. To modify an Ex command before
-    evaluating it, use |nvim_parse_cmd()| in conjunction with |nvim_cmd()|.
+    Prefer |nvim_cmd()| or |nvim_exec2()| instead. To modify an Ex command in
+    a structured way before executing it, modify the result of
+    |nvim_parse_cmd()| then pass it to |nvim_cmd()|.
 
     Parameters: ~
       • {command}  Ex command string
diff --git a/runtime/lua/vim/_meta/api.lua b/runtime/lua/vim/_meta/api.lua
index b2385197bd..55274963ed 100644
--- a/runtime/lua/vim/_meta/api.lua
+++ b/runtime/lua/vim/_meta/api.lua
@@ -885,10 +885,8 @@ function vim.api.nvim_cmd(cmd, opts) end
 ---
 --- On execution error: fails with Vimscript error, updates v:errmsg.
 ---
---- Prefer using `nvim_cmd()` or `nvim_exec2()` over this. To evaluate multiple lines of Vim script
---- or an Ex command directly, use `nvim_exec2()`. To construct an Ex command using a structured
---- format and then execute it, use `nvim_cmd()`. To modify an Ex command before evaluating it, use
---- `nvim_parse_cmd()` in conjunction with `nvim_cmd()`.
+--- Prefer `nvim_cmd()` or `nvim_exec2()` instead. To modify an Ex command in a structured way
+--- before executing it, modify the result of `nvim_parse_cmd()` then pass it to `nvim_cmd()`.
 ---
 --- @param command string Ex command string
 function vim.api.nvim_command(command) end