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.
The manual is written in https://asciidoc.org[AsciiDoc] and includes some extra files which are generated from the source code. Run `cargo test` and `cargo test -p xtask` to create these and then `asciidoctor manual.adoc` to create an HTML copy.
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.
You can download pre-built binaries from the https://github.com/rust-analyzer/rust-analyzer/releases[releases] page.
You will need to uncompress and rename the binary for your platform, e.g. from `rust-analyzer-aarch64-apple-darwin.gz` on Mac OS to `rust-analyzer`, make it executable, then move 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.
However, in contrast to `component add clippy` or `component add rustfmt`, this does not actually place a `rust-analyzer` binary in `~/.cargo/bin`, see https://github.com/rust-lang/rustup/issues/2411[this issue].
`rust-analyzer` is available in the GURU repository:
- https://gitweb.gentoo.org/repo/proj/guru.git/tree/dev-util/rust-analyzer-bin/rust-analyzer-bin-9999.ebuild[`dev-util/rust-analyzer-bin-9999`] (the https://github.com/rust-analyzer/rust-analyzer/releases/latest[latest release] as a live binary ebuild)
If not already, GURU must be enabled (e.g. using `app-eselect/eselect-repository`) and sync'd before running `emerge`:
[source,bash]
----
$ eselect repository enable guru && emaint sync -r guru
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].
Note: for code actions, use `coc-codeaction-cursor` and `coc-codeaction-selected`; `coc-codeaction` and `coc-codeaction-line` are unlikely to be useful.
vim-lsp is installed by following https://github.com/prabirshrestha/vim-lsp[the plugin instructions].
It can be as simple as adding this line to your `.vimrc`:
[source,vim]
----
Plug 'prabirshrestha/vim-lsp'
----
Next you need to register the `rust-analyzer` binary.
If it is available in `$PATH`, you may want to add this to your `.vimrc`:
[source,vim]
----
if executable('rust-analyzer')
au User lsp_setup call lsp#register_server({
\ 'name': 'Rust Language Server',
\ 'cmd': {server_info->['rust-analyzer']},
\ 'whitelist': ['rust'],
\ })
endif
----
There is no dedicated UI for the server configuration, so you would need to send any options as a value of the `initialization_options` field, as described in the <<_configuration,Configuration>> section.
Here is an example of how to enable the proc-macro support:
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.
If `rust-analyzer` is not detected, Corrosion will prompt you for configuration of your Rust toolchain and language server with a link to the __Window > Preferences > Rust__ preference page; from here a button allows to download and configure `rust-analyzer`, but you can also reference another installation.
https://gitlab.com/cppit/jucipp[juCi++] has built-in support for the language server protocol, and since version 1.7.0 offers installation of both Rust and rust-analyzer when opening a Rust file.
The <<_installation,Installation>> section contains details on configuration for some of the editors.
In general `rust-analyzer` is configured via LSP messages, which means that it's up to the editor to decide on the exact format and location of configuration files.
Some clients, such as <<vs-code,VS Code>> or <<coc-rust-analyzer,COC plugin in Vim>> provide `rust-analyzer` specific configuration UIs. Others may require you to know a bit more about the interaction with `rust-analyzer`.
For the later category, it might help to know that the initial configuration is specified as a value of the `initializationOptions` field of the https://microsoft.github.io/language-server-protocol/specifications/specification-current/#initialize[`InitializeParams` message, in the LSP protocol].
The spec says that the field type is `any?`, but `rust-analyzer` is looking for a JSON object that is constructed using settings from the list below.
Name of the setting, ignoring the `rust-analyzer.` prefix, is used as a path, and value of the setting becomes the JSON property value.
For example, a very common configuration is to enable proc-macro support, can be achieved by sending this JSON:
[source,json]
----
{
"cargo": {
"loadOutDirsFromCheck": true,
},
"procMacro": {
"enable": true,
}
}
----
Please consult your editor's documentation to learn more about how to configure https://microsoft.github.io/language-server-protocol/[LSP servers].
To verify which configuration is actually used by `rust-analyzer`, set `RA_LOG` environment variable to `rust_analyzer=info` and look for config-related messages.
Logs should show both the JSON that `rust-analyzer` sees as well as the updated config.
This is the list of config options `rust-analyzer` supports:
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:
* 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).
Note that calls to `cargo check` are disabled when using `rust-project.json` by default, so compilation errors and warnings will no longer be sent to your LSP client. To enable these compilation errors you will need to specify explicitly what command rust-analyzer should run to perform the checks using the `checkOnSave.overrideCommand` configuration. As an example, the following configuration explicitly sets `cargo check` as the `checkOnSave` command.
The `checkOnSave.overrideCommand` requires the command specified to output json error messages for rust-analyzer to consume. The `--message-format=json` flag does this for `cargo check` so whichever command you use must also output errors in this format. See the <<Configuration>> section for more information.
* VS Code plugin reads configuration from project directory, and that can be used to override paths to various executables, like `rustfmt` or `rust-analyzer` itself.
* rust-analyzer's syntax trees library uses a lot of `unsafe` and hasn't been properly audited for memory safety.
The LSP server performs no network access in itself, but runs `cargo metadata` which will update or download the crate registry and the source code of the project dependencies.
If enabled (the default), build scripts and procedural macros can do anything.
The Code extension automatically connects to GitHub to download updated LSP binaries and, if the nightly channel is selected, to perform update checks using the GitHub API. For `rust-analyzer` developers, using `cargo xtask release` uses the same API to put together the release notes.
Any other editor plugins are not under the control of the `rust-analyzer` developers. For any privacy concerns, you should check with their respective developers.
While most errors and warnings provided by rust-analyzer come from the `cargo check` integration, there's a growing number of diagnostics implemented using rust-analyzer's own analysis.
Some of these diagnostics don't respect `\#[allow]` or `\#[deny]` attributes yet, but can be turned off using the `rust-analyzer.diagnostics.enable`, `rust-analyzer.diagnostics.enableExperimental` or `rust-analyzer.diagnostics.disabled` settings.
Most themes doesn't support styling unsafe operations differently yet. You can fix this by adding overrides for the rules `operator.unsafe`, `function.unsafe`, and `method.unsafe`:
In addition to the top-level rules you can specify overrides for specific themes. For example, if you wanted to use a darker text color on a specific light theme, you might write:
You can use any valid regular expression 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 built-in `cargo check`, you can configure Code to run a command in the background and use the `$rustc-watch` problem matcher to generate inline error markers from its output.
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.
