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.
* To log all LSP requests, add `"rust-analyzer.trace.server": "verbose"` to the settings and look for `Rust Analyzer Language Server Trace` in the panel.
* To enable client-side logging, add `"rust-analyzer.trace.extension": true` to the settings and open `Output > Rust Analyzer Client` in the panel.
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 `$PATH` as the shell, see https://github.com/rust-analyzer/rust-analyzer/issues/1811[this issue].
On Unix, running the editor from a shell or changing the `.desktop` file to set the environment should help.
Emacs support is maintained as part of the https://github.com/emacs-lsp/lsp-mode[Emacs-LSP] package in https://github.com/emacs-lsp/lsp-mode/blob/master/lsp-rust.el[lsp-rust.el].
1. Install the most recent version of `emacs-lsp` package by following the https://github.com/emacs-lsp/lsp-mode[Emacs-LSP instructions].
Note: for code actions, use `coc-codeaction-cursor` and `coc-codeaction-selected`; `coc-codeaction` and `coc-codeaction-line` are unlikely to be useful.
vim-lsp is installed by following https://github.com/prabirshrestha/vim-lsp[the plugin instructions].
It can be as simple as adding this line to your `.vimrc`:
[source,vim]
----
Plug 'prabirshrestha/vim-lsp'
----
Next you need to register the `rust-analyzer` binary.
If it is available in `$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.
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:
/// 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).
* proc macros and build scripts are executed by default
* `.cargo/config` can override `rustc` with an arbitrary executable
* 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.
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.
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.
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.
