This manual focuses on a specific usage of the library -- running it as part of a server that implements the
https://microsoft.github.io/language-server-protocol/[Language Server Protocol] (LSP).
The LSP allows various code editors, like VS Code, Emacs or Vim, to implement semantic features like completion or goto definition by talking to an external language server process.
If you have questions about using rust-analyzer, please ask them in the https://users.rust-lang.org/c/ide/14["`IDEs and Editors`"] topic of Rust users forum.
In theory, one should be able to just install the <<rust-analyzer-language-server-binary,`rust-analyzer` binary>> and have it automatically work with any editor.
The extension will be updated automatically as new versions become available. It will ask your permission to download the matching language server version binary if needed.
We ship nightly releases for VS Code. To help us out with testing the newest code and follow the bleeding edge of our `master`, please use the following config:
You will be prompted to install the `nightly` extension version. Just click `Download now` and from that moment you will get automatic updates every 24 hours.
You can download the pre-built binary from the https://github.com/rust-analyzer/rust-analyzer/releases[releases] page.
Typically, you then need to rename the binary for your platform, e.g. `rust-analyzer-mac` if you're on Mac OS, to `rust-analyzer` and make it executable in addition to moving it into a directory in your `$PATH`.
If your editor can't find the binary even though the binary is on your `$PATH`, the likely explanation is that it doesn't see the same `$PATH` as the shell, see https://github.com/rust-analyzer/rust-analyzer/issues/1811[this issue].
On Unix, running the editor from a shell or changing the `.desktop` file to set the environment should help.
Emacs support is maintained as part of the https://github.com/emacs-lsp/lsp-mode[Emacs-LSP] package in https://github.com/emacs-lsp/lsp-mode/blob/master/lsp-rust.el[lsp-rust.el].
1. Install the most recent version of `emacs-lsp` package by following the https://github.com/emacs-lsp/lsp-mode[Emacs-LSP instructions].
Prerequisites: You have installed the <<rust-analyzer-language-server-binary,`rust-analyzer` binary>>. Not needed if the extension can install/update it on its own, coc-rust-analyzer is one example.
Finally, with your Rust project open, in the command palette, run `LSP: Enable Language Server In Project` or `LSP: Enable Language Server Globally`, then select `rust-analyzer` in the list that pops up to enable the rust-analyzer LSP. The latter means that rust-analyzer is enabled by default in Rust projects.
If it worked, you should see "rust-analyzer, Line X, Column Y" on the left side of the bottom bar, and after waiting a bit, functionality like tooltips on hovering over variables should become available.
If you get an error saying `No such file or directory: 'rust-analyzer'`, see the <<rust-analyzer-language-server-binary,`rust-analyzer` binary>> section on installing the language server binary.
Prerequisites: You have installed the <<rust-analyzer-language-server-binary,`rust-analyzer` binary>>.
Gnome Builder currently has support for RLS, and there's no way to configure the language server executable. A future version might support `rust-analyzer` out of the box.
1. Rename, symlink or copy the `rust-analyzer` binary to `rls` and place it somewhere Builder can find (in `PATH`, or under `~/.cargo/bin`).
https://nightly.gnome.org/repo/appstream/org.gnome.Builder.flatpakref[GNOME Builder (Nightly)] has now native support for `rust-analyzer` out of the box. If the `rust-analyzer` binary is not available, GNOME Builder can install it when opening a Rust source file.
However, if you use some other build system, you'll have to describe the structure of your project for rust-analyzer in the `rust-project.json` format:
[source,TypeScript]
----
interface JsonProject {
/// The set of paths containing the crates for this project.
/// Any `Crate` must be nested inside some `root`.
roots: string[];
/// The set of crates comprising the current project.
/// Must include all transitive dependencies as well as sysroot crate (libstd, libcore and such).
crates: Crate[];
}
interface Crate {
/// Path to the root module of the crate.
root_module: string;
/// Edition of the crate.
edition: "2015" | "2018";
/// Dependencies
deps: Dep[];
/// The set of cfgs activated for a given crate, like `["unix", "feature=foo", "feature=bar"]`.
cfg: string[];
/// value of the OUT_DIR env variable.
out_dir?: string;
/// For proc-macro crates, path to compiles proc-macro (.so file).
proc_macro_dylib_path?: string;
}
interface Dep {
/// Index of a crate in the `crates` array.
crate: number,
/// Name as should appear in the (implicit) `extern crate name` declaration.
name: string,
}
----
This format is provisional and subject to change.
Specifically, the `roots` setup will be different eventually.
There are tree ways to feed `rust-project.json` to rust-analyzer:
* Place `rust-project.json` file at the root of the project, and rust-anlayzer will discover it.
* Specify `"rust-analyzer.linkedProjects": [ "path/to/rust-project.json" ]` in the settings (and make sure that your LSP client sends settings as a part of initialize request).
You can use any valid RegExp as a mask. Also note that a full runnable name is something like *run bin_or_example_name*, *test some::mod::test_name* or *test-mod some::mod*, so it is possible to distinguish binaries, single tests, and test modules with this masks: `"^run"`, `"^test "` (the trailing space matters!), and `"^test-mod"` respectively.
Instead of relying on the builtin `cargo check`, rust-analyzer can run a command in the background and use the `$rustc-watch` problem matcher to parse its output to generate inline error markers.
To do this you need to create a new https://code.visualstudio.com/docs/editor/tasks[VS Code Task] and set `rust-analyzer.checkOnSave.enable: false` in preferences.
For example, if you want to run https://crates.io/crates/cargo-watch[`cargo watch`] instead you might add the following to `.vscode/tasks.json`:
