Files
neovim/test/old/testdir
zeertzjq f7af0cff35 vim-patch:9.1.1590: cannot perform autocompletion (#35141)
Problem:  cannot perform autocompletion
Solution: Add the 'autocomplete' option value
          (Girish Palya)

This change introduces the 'autocomplete' ('ac') boolean option to
enable automatic popup menu completion during insert mode. When enabled,
Vim shows a completion menu as you type, similar to pressing |i\_CTRL-N|
manually. The items are collected from sources defined in the
'complete' option.

To ensure responsiveness, this feature uses a time-sliced strategy:

- Sources earlier in the 'complete' list are given more time.
- If a source exceeds its allocated timeout, it is interrupted.
- The next source is then started with a reduced timeout (exponentially
  decayed).
- A small minimum ensures every source still gets a brief chance to
  contribute.

The feature is fully compatible with other |i_CTRL-X| completion modes,
which can temporarily suspend automatic completion when triggered.

See :help 'autocomplete' and :help ins-autocompletion for more details.

To try it out, use :set ac

You should see a popup menu appear automatically with suggestions. This
works seamlessly across:

- Large files (multi-gigabyte size)
- Massive codebases (:argadd thousands of .c or .h files)
- Large dictionaries via the `k` option
- Slow or blocking LSP servers or user-defined 'completefunc'

Despite potential slowness in sources, the menu remains fast,
responsive, and useful.

Compatibility: This mode is fully compatible with existing completion
methods. You can still invoke any CTRL-X based completion (e.g.,
CTRL-X CTRL-F for filenames) at any time (CTRL-X temporarily
suspends 'autocomplete'). To specifically use i_CTRL-N, dismiss the
current popup by pressing CTRL-E first.

---

How it works

To keep completion snappy under all conditions, autocompletion uses a
decaying time-sliced algorithm:

- Starts with an initial timeout (80ms).
- If a source does not complete within the timeout, it's interrupted and
  the timeout is halved for the next source.
- This continues recursively until a minimum timeout (5ms) is reached.
- All sources are given a chance, but slower ones are de-prioritized
  quickly.

Most of the time, matches are computed well within the initial window.

---

Implementation details

- Completion logic is mostly triggered in `edit.c` and handled in
  insexpand.c.

- Uses existing inc_compl_check_keys() mechanism, so no new polling
  hooks are needed.

- The completion system already checks for user input periodically; it
  now also checks for timer expiry.

---

Design notes

- The menu doesn't continuously update after it's shown to prevent
  visual distraction (due to resizing) and ensure the internal list
  stays synchronized with the displayed menu.

- The 'complete' option determines priority—sources listed earlier get
  more time.

- The exponential time-decay mechanism prevents indefinite collection,
  contributing to low CPU usage and a minimal memory footprint.

- Timeout values are intentionally not configurable—this system is
  optimized to "just work" out of the box. If autocompletion feels slow,
  it typically indicates a deeper performance bottleneck (e.g., a slow
  custom function not using `complete_check()`) rather than a
  configuration issue.

---

Performance

Based on testing, the total roundtrip time for completion is generally
under 200ms. For common usage, it often responds in under 50ms on an
average laptop, which falls within the "feels instantaneous" category
(sub-100ms) for perceived user experience.

| Upper Bound (ms) | Perceived UX
|----------------- |-------------
| <100 ms          | Excellent; instantaneous
| <200 ms          | Good; snappy
| >300 ms          | Noticeable lag
| >500 ms          | Sluggish/Broken

---

Why this belongs in core:

- Minimal and focused implementation, tightly integrated with existing
  Insert-mode completion logic.
- Zero reliance on autocommands and external scripting.
- Makes full use of Vim’s highly composable 'complete' infrastructure
  while avoiding the complexity of plugin-based solutions.
- Gives users C native autocompletion with excellent responsiveness and
  no configuration overhead.
- Adds a key UX functionality in a simple, performant, and Vim-like way.

closes: vim/vim#17812

af9a7a04f1

Co-authored-by: Girish Palya <girishji@gmail.com>
2025-08-03 11:48:42 +08:00
..
2024-04-23 18:17:04 +02:00
2024-03-28 09:32:32 +08:00

This directory contains tests for various Vim features.
For testing an indent script see runtime/indent/testdir/README.txt.

If it makes sense, add a new test method to an already existing file.  You may
want to separate it from other tests with comment lines.

TO ADD A NEW STYLE TEST:

1) Create a test_<subject>.vim file.
2) Add test_<subject>.res to NEW_TESTS_RES in Make_all.mak in alphabetical
   order.
3) Also add an entry "test_<subject>" to NEW_TESTS in Make_all.mak.
4) Use make test_<subject> to run a single test.

At 2), instead of running the test separately, it can be included in
"test_alot".  Do this for quick tests without side effects.  The test runs a
bit faster, because Vim doesn't have to be started, one Vim instance runs many
tests.

At 4), to run a test in GUI, add "GUI_FLAG=-g" to the make command.


What you can use (see test_assert.vim for an example):

- Call assert_equal(), assert_true(), assert_false(), etc.

- Use assert_fails() to check for expected errors.

- Use try/catch to avoid an exception aborts the test.

- Use test_alloc_fail() to have memory allocation fail.  This makes it possible
  to check memory allocation failures are handled gracefully.  You need to
  change the source code to add an ID to the allocation.  Add a new one to
  alloc_id_T, before aid_last.

- Use test_override() to make Vim behave differently, e.g.  if char_avail()
  must return FALSE for a while.  E.g. to trigger the CursorMovedI autocommand
  event. See test_cursor_func.vim for an example.

- If the bug that is being tested isn't fixed yet, you can throw an exception
  with "Skipped" so that it's clear this still needs work.  E.g.: throw
  "Skipped: Bug with <c-e> and popupmenu not fixed yet"

- The following environment variables are recognized and can be set to
  influence the behavior of the test suite (see runtest.vim for details)

  - $TEST_MAY_FAIL=Test_channel_one    - ignore those failing tests
  - $TEST_FILTER=Test_channel    - only run test that match this pattern
  - $TEST_SKIP_PAT=Test_channel  - skip tests that match this pattern
  - $TEST_NO_RETRY=yes           - do not try to re-run failing tests
  You can also set them in Vim:
    :let $TEST_MAY_FAIL = 'Test_channel_one'
    :let $TEST_FILTER = '_set_mode'
    :let $TEST_SKIP_PAT = 'Test_loop_forever'
    :let $TEST_NO_RETRY = 'yes'
  Use an empty string to revert, e.g.:
    :let $TEST_FILTER = ''

- See the start of runtest.vim for more help.


TO ADD A SCREEN DUMP TEST:

Mostly the same as writing a new style test.  Additionally, see help on
"terminal-dumptest".  Put the reference dump in "dumps/Test_func_name.dump".


OLD STYLE TESTS:

There are a few tests that are used when Vim was built without the +eval
feature.  These cannot use the "assert" functions, therefore they consist of a
.in file that contains Normal mode commands between STARTTEST and ENDTEST.
They modify the file and the result gets written in the test.out file.  This
is then compared with the .ok file.  If they are equal the test passed.  If
they differ the test failed.


RUNNING THE TESTS:

To run a single test from the src directory:

    $ make test_<name>

The below commands should be run from the src/testdir directory.

To run a single test:

    $ make test_<name>.res

The file 'messages' contains the messages generated by the test script.  If a
test fails, then the test.log file contains the error messages.  If all the
tests are successful, then this file will be an empty file.

- To run a single test function from a test script:

    $ ../vim -u NONE -S runtest.vim <test_file>.vim <function_name>

- To execute only specific test functions, add a second argument:

	 $ ../vim -u NONE -S runtest.vim test_channel.vim open_delay


- To run all the tests:

    $ make

- To run the test on MS-Windows using the MSVC nmake:

    > nmake -f Make_dos.mak

- To run the tests with GUI Vim:

    $ make GUI_FLAG=-g

    or

    $ make VIMPROG=../gvim

- To cleanup the temporary files after running the tests:

    $ make clean