fix(exceptions): restore `did_throw` (#20000)

`!did_throw` doesn't exactly imply `!current_exception`, as `did_throw = false`
is sometimes used to defer exception handling for later (without forgetting the
exception). E.g: uncaught exception handling in `do_cmdline()` may be deferred
to a different call (e.g: when `try_level > 0`).

In #7881, `current_exception = NULL` in `do_cmdline()` is used as an analogue of
`did_throw = false`, but also causes the pending exception to be lost, which
also leaks as `discard_exception()` wasn't used.

It may be possible to fix this by saving/restoring `current_exception`, but
handling all of `did_throw`'s edge cases seems messier. Maybe not worth
diverging over.

This fix also uncovers a `man_spec.lua` bug on Windows: exceptions are thrown
due to Windows missing `man`, but they're lost; skip these tests if `man` isn't
executable.

1 files changed, 1 insertions, 0 deletions

diff --git a/src/nvim/api/private/helpers.h b/src/nvim/api/private/helpers.h
index 4608554448..2157ad0ec2 100644
--- a/src/nvim/api/private/helpers.h
+++ b/src/nvim/api/private/helpers.h
@@ -134,6 +134,7 @@ typedef struct {
   const msglist_T *const *msg_list;
   int trylevel;
   int got_int;
+  bool did_throw;
   int need_rethrow;
   int did_emsg;
 } TryState;