Problem:
Undo places the cursor wherever the cursor happened to sit at "save
time" (`uh_cursor` is sampled lazily on the first change).
Examples:
- `i` preserves, but `a` does not
- `diw`, `atest<Esc>`, `d^` abandon the original position
- `D`, `o` restore it (by accident).
Solution:
`composite` tracks the pending atom (and its `origin`) across frames.
A `stuffed` continuation frame inherits the `origin` + prepped redo.
Store `origin` info in the undo header, so undo can restore it.
- Not for a mid-command undo break (i_CTRL-G_u).
- Undoing a mapping restores where the mapping started (which
technically may be different than where the "edit" started).
Problem:
`:rundo` on a corrupted undo file crashes or hangs, instead of failing
with E825. Patching one 4-byte field is enough:
ue_size = 0xFFFFFFFF " walks a NULL ue_array
ue_size = 0x7FFFFFF0 " 17 GB xmalloc + memset, then preserve_exit()
ue_top = 0xFFFFFFFB " negative lnum reaches ml_delete()
Analysis:
Every count in the file is read with `undo_read_4c()` and then checked,
differently at each site. None bounds the value by what the file can
hold, so a 2 GB count reaches `xmalloc()`.
Note:
- Vim doesn't have `bi_fsize` because it checks `U_ALLOC_LINE` result
everywhere (thus doesn't crash, but may thrash...); those checks were
dropped when Nvim moved to `xmalloc()`, and the `ue_size` loop counter
became unsigned.
- Vim *does* have the negative line numbers bug: `u_undoredo()` checks
`top > ml_line_count || top >= bot || bot > ml_line_count + 1`, which
rejects none of them.
Solution:
- Introduce `undo_read_len()` and use it to fail early instead of
continuing with nonsense.
- Validate `ue_top`/`ue_bot`/ `ue_lcount`.
- Use `xcalloc()`, so no site can proceed with a NULL array.
- Report a truncated "U" line, distinguish EOF from a 0xFFFFFFFF field,
and free the header on the extmark error path.
Problem:
The magic globals `it`, `describe`, etc., are more trouble than they are
worth.
- Hooking into `after_each` requires `getfenv()` hacks.
- They confuse luals/emmylua, because the top-level `.luarc.json` isn't
merged with `test/.luarc.json` (apparently a luals limitation?)
- They totally defeat discoverability because the user just has to
"know" about the various magic symbols.
So they harm DX, which means they serve no purpose at all.
Solution:
- Expose the test API from `testutil`, so tests can call `t.it()`,
`t.describe()`, etc., in the conventional way.
- Drop `getfenv()` hacks.
- Drop the `setfenv()` injection in `load_chunk`.
- Drop `test/_meta.lua`.
Problem: Undefined behavior when 'undodir' contains empty entry.
Solution: Don't try to remove trailing slashes from empty path. Also
don't remove a colon on Windows while at it.
Problem: undoing after the prompt is changed breaks it (and causes init_prompt
to abort it and append a new one), as the undo history contains the old prompt.
Solution: like submitting, clear the undo buffer. Don't do it in init_prompt if
the line was empty; that may not result in a new prompt, and causes commands
like "S" to lose the history.
As u_save, etc. wasn't being called by prompt_setprompt, undoing after it fixes
the prompt usually gave undesirable results anyway.
Remove the added undo_spec.lua test, as its approach no longer works as a repro,
and finding a new one seems fiddly.
Specifically, functions that are run in the context of the test runner
are put in module `test/testutil.lua` while the functions that are run
in the context of the test session are put in
`test/functional/testnvim.lua`.
Closes https://github.com/neovim/neovim/issues/27004.
Problem:
Subdirectories like "visual", "insert", "normal" encourage people to
separate *related* tests for no good reason. Typically the _mode_ is
not the relevant topic of a test (and when it is, _then_ create
an appropriate describe() or it()).
Solution:
- Delete the various `test/functional/<mode>/` subdirectories, move
their tests to more meaningful topics.
- Rename `…/normal/` to `…/editor/`.
- Move or merge `…/visual/*` and `…/insert/*` tests into here where
appropriate.
- Rename `…/eval/` to `…/vimscript/`.
- Move `…/viml/*` into here also.
* test(reorg): insert/* => editor/mode_insert_spec.lua
* test(reorg): cmdline/* => editor/mode_cmdline_spec.lua
* test(reorg): eval core tests => eval_spec.lua
