Code at the speed of thought – Zed is a high-performance, multiplayer code editor from the creators of Atom and Tree-sitter.
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Max Brunsfeld e67c44a562
Fix file-reloading race condition (#3348)
### Summary

This PR fixes a bug that @as-cii and @osiewicz saw when the on-disk
contents of files changed due to running `git checkout` at the command
line. It caused a buffer's contents to diverge from the file's on disk
contents, but the buffer to show an *unmodified* status.

I've also introduced new APIs on gpui's deterministic executor, which
make it possible to write a test that reliably triggered the bug.

### Details

The bug is triggered by the following sequence of events:
1. A buffer's file changes on disk while the buffer is *unmodified*
2. Zed reloads the new content of the file
3. Before updating the buffer itself, Zed computes a *diff* between the
buffer's current contents, and the newly-loaded contents
4. While this diff is being computed, one of two things happens:
     1. the buffer changes on-disk *again*.
2. the user edits the buffer, but undoes the edit, so that the buffer
returns to an unmodified state

The bug itself was caused by a few things:
* The buffer diffing algorithm is pretty slow, because we perform a
character-wise diff
* We previously allowed multiple reload tasks to run concurrently
* When discarding an out-of-date diff, we failed to update parts of the
buffer's state (`saved_fingerprint`) which allow us to recognize that
the buffer's content differs from the file.

It was also difficult to reproduce the problem in tests, because under
deterministic execution, because it was extremely unlikely for other
tasks to make progress *after* a file had been reloaded, but *before*
the disk task has resolved. To help with testing, I introduced a pair of
executor APIs:

`spawn_labeled`, - for spawning a background task with a given *label*
`deprioritize_task` - for forcing tasks with a given label to run
*after* all other concurrent tasks.

I also made the `Model::next_event` test helper method more useful, in
that it no longer runs *until* parked in order to wait for the next
event to occur. It just steps the executor one poll at a time until the
model emits an event.

Release Notes:

- Fixed a bug that caused buffers to report incorrect modified/conflict
status when their buffers changed on disk multiple times in rapid
succession.
2023-11-16 20:19:16 -08:00
.cargo
.config
.github Don't generate licenses on every PR 2023-11-07 14:33:19 -07:00
.vscode
.zed
assets Revert change to default buffer font size 2023-11-16 13:13:03 -05:00
crates Fix file-reloading race condition (#3348) 2023-11-16 20:19:16 -08:00
docs
plugins
script Fix typo in EULA 2023-11-09 11:08:30 -05:00
styles MODAL 2023-11-07 13:23:27 -07:00
.dockerignore
.gitignore Add Noctis Theme 2023-11-06 12:43:10 -05:00
.gitmodules
Cargo.lock Salvage old distributed slice code 2023-11-16 10:32:55 -08:00
Cargo.toml Add an actual context menu into terminal-2 2023-11-16 16:36:44 +02:00
Dockerfile
Procfile
README.md
rust-toolchain.toml
test.rs Account for element's bounds in Editor::bounds_for_range 2023-11-08 16:15:10 -08:00

Zed

CI

Welcome to Zed, a lightning-fast, collaborative code editor that makes your dreams come true.

Development tips

Dependencies

  • Install Xcode from https://apps.apple.com/us/app/xcode/id497799835?mt=12, and accept the license:

    sudo xcodebuild -license
    
  • Install homebrew, node and rustup-init (rustup, rust, cargo, etc.)

    /bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"
    brew install node rustup-init
    rustup-init # follow the installation steps
    
  • Install postgres and configure the database

    brew install postgresql@15
    brew services start postgresql@15
    psql -c "CREATE ROLE postgres SUPERUSER LOGIN" postgres
    psql -U postgres -c "CREATE DATABASE zed"
    
  • Install the LiveKit server, the PostgREST API server, and the foreman process supervisor:

    brew install livekit
    brew install postgrest
    brew install foreman
    
  • Ensure the Zed.dev website is checked out in a sibling directory and install its dependencies:

    cd ..
    git clone https://github.com/zed-industries/zed.dev
    cd zed.dev && npm install
    npm install -g vercel
    
  • Return to Zed project directory and Initialize submodules

    cd zed
    git submodule update --init --recursive
    
  • Set up a local zed database and seed it with some initial users:

    Create a personal GitHub token to run script/bootstrap once successfully: the token needs to have an access to private repositories for the script to work (repo OAuth scope). Then delete that token.

    GITHUB_TOKEN=<$token> script/bootstrap
    
  • Now try running zed with collaboration disabled:

    cargo run
    

Common errors

  • xcrun: error: unable to find utility "metal", not a developer tool or in PATH

Testing against locally-running servers

Start the web and collab servers:

foreman start

If you want to run Zed pointed at the local servers, you can run:

script/zed-local

Dump element JSON

If you trigger cmd-alt-i, Zed will copy a JSON representation of the current window contents to the clipboard. You can paste this in a tool like DJSON to navigate the state of on-screen elements in a structured way.

Licensing

We use cargo-about to automatically comply with open source licenses. If CI is failing, check the following:

  • Is it showing a no license specified error for a crate you've created? If so, add publish = false under [package] in your crate's Cargo.toml.
  • Is the error failed to satisfy license requirements for a dependency? If so, first determine what license the project has and whether this system is sufficient to comply with this license's requirements. If you're unsure, ask a lawyer. Once you've verified that this system is acceptable add the license's SPDX identifier to the accepted array in script/licenses/zed-licenses.toml.
  • Is cargo-about unable to find the license for a dependency? If so, add a clarification field at the end of script/licenses/zed-licenses.toml, as specified in the cargo-about book.

Wasm Plugins

Zed has a Wasm-based plugin runtime which it currently uses to embed plugins. To compile Zed, you'll need to have the wasm32-wasi toolchain installed on your system. To install this toolchain, run:

rustup target add wasm32-wasi

Plugins can be found in the plugins folder in the root. For more information about how plugins work, check the Plugin Guide in crates/plugin_runtime/README.md.