zed/crates/vim
Ali 00c0e96e76
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Make opening large files use less peak memory (#62748)
# Objective
Opening a file laods it twice. `decode_file_text` builds the whole file
as a `String`, and that `String` stays alive alongside the finished rope
while `text::Buffer::new` copies it in. The `Vec` behind it grows by
doubling, so it also commits up to nearly the file's size again in
capacity it never uses.

Partially addresses #27283.

## Solution

Add `decode_file_text_to_rope`, which streams the file in 1 MB blocks
straight into a `Rope`, validating UTF-8 and normalizing line endings as
it goes. The file is never fully held as a `String`.

`LoadedFile::text` becomes a `Rope` carrying the `LineEnding` detected
before normalizing, so `buffer_store` calls `Buffer::new_normalized`.

## Testing

On a 729 MB SQL dump, peak memory fell 25% and CPU fell around 28%.
tested on 5950x, win11.

Release Notes:

- Improved memory use when opening large files, reducing peak memory
during load by roughly the size of the file itself.
2026-08-18 16:59:08 +00:00
..
src Make opening large files use less peak memory (#62748) 2026-08-18 16:59:08 +00:00
test_data vim: Fix cw with count greater than 1 not preserving whitespace correctly (#56585) 2026-06-18 14:50:31 +00:00
Cargo.toml theme: Split out theme_settings crate (#52569) 2026-03-27 14:41:25 +01:00
LICENSE-GPL
README.md

This contains the code for Zed's Vim emulation mode.

Vim mode in Zed is supposed to primarily "do what you expect": it mostly tries to copy vim exactly, but will use Zed-specific functionality when available to make things smoother. This means Zed will never be 100% vim compatible, but should be 100% vim familiar!

The backlog is maintained in the #vim channel notes.

Testing against Neovim

If you are making a change to make Zed's behavior more closely match vim/nvim, you can create a test using the NeovimBackedTestContext.

For example, the following test checks that Zed and Neovim have the same behavior when running * in visual mode:

#[gpui::test]
async fn test_visual_star_hash(cx: &mut gpui::TestAppContext) {
    let mut cx = NeovimBackedTestContext::new(cx).await;

    cx.set_shared_state("ˇa.c. abcd a.c. abcd").await;
    cx.simulate_shared_keystrokes(["v", "3", "l", "*"]).await;
    cx.assert_shared_state("a.c. abcd ˇa.c. abcd").await;
}

To keep CI runs fast, by default the neovim tests use a cached JSON file that records what neovim did (see crates/vim/test_data), but while developing this test you'll need to run it with the neovim flag enabled:

cargo test -p vim --features neovim test_visual_star_hash

This will run your keystrokes against a headless neovim and cache the results in the test_data directory. Note that neovim must be installed and reachable on your $PATH in order to run the feature.

Testing zed-only behavior

Zed does more than vim/neovim in their default modes. The VimTestContext can be used instead. This lets you test integration with the language server and other parts of zed's UI that don't have a NeoVim equivalent.