fix(options): validate nvim_set_option_value() dry runs

Problem:

nvim_set_option_value() with dry_run=true accepts invalid values such as
foldmethod='nonsense'. Validation is mixed with side effects in the
did_set_* callbacks, so dry runs skip it.

Solution:

Split value validation out of the did_set_* callbacks into separate
validation_cb callbacks. Use these checks for both normal assignments
and nvim_set_option_value() dry runs. Keep side effects in did_set_*.

Replace direct foldenable/foldlevel assignments in C folding commands
with setters. This gives C commands the same OptionSet and
synchronization behavior as Lua assignments.

Use normal setters for 'tabstop' and 'vartabstop' in :retab so C code
indentation and folds based on indentation use the new tab widths.
Direct assignments could leave them using the old widths.

:retab temporarily turns off 'list' to calculate tab widths. Previously,
:retab -1 reported an error and returned without restoring 'list'. Check
the argument before turning 'list' off, so an invalid argument leaves
the option unchanged.

AI-assisted

0 files changed, 0 insertions, 0 deletions