rust/docs/user/manual.adoc

= User Manual
:toc: preamble
:sectanchors:
:page-layout: post
:icons: font
:source-highlighter: rouge
:experimental:

////
IMPORTANT: the master copy of this document lives in the https://github.com/rust-lang/rust-analyzer repository
////

At its core, rust-analyzer is a *library* for semantic analysis of Rust code as it changes over time.
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.

[TIP]
====
[.lead]
To improve this document, send a pull request: +
https://github.com/rust-lang/rust-analyzer/blob/master/docs/user/manual.adoc[https://github.com/rust-analyzer/.../manual.adoc]

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.

== Installation

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.
We are not there yet, so some editor specific setup is required.

Additionally, rust-analyzer needs the sources of the standard library.
If the source code is not present, rust-analyzer will attempt to install it automatically.

To add the sources manually, run the following command:

```bash
$ rustup component add rust-src
```

=== Toolchain

Only the latest stable standard library source is officially supported for use with rust-analyzer.
If you are using an older toolchain or have an override set, rust-analyzer may fail to understand the Rust source.
You will either need to update your toolchain or use an older version of rust-analyzer that is compatible with your toolchain.

If you are using an override in your project, you can still force rust-analyzer to use the stable toolchain via the environment variable `RUSTUP_TOOLCHAIN`.
For example, with VS Code or coc-rust-analyzer:

[source,json]
----
{ "rust-analyzer.server.extraEnv": { "RUSTUP_TOOLCHAIN": "stable" } }
----

=== VS Code

This is the best supported editor at the moment.
The rust-analyzer plugin for VS Code is maintained
https://github.com/rust-lang/rust-analyzer/tree/master/editors/code[in tree].

You can install the latest release of the plugin from
https://marketplace.visualstudio.com/items?itemName=rust-lang.rust-analyzer[the marketplace].

Note that the plugin may cause conflicts with the
https://marketplace.visualstudio.com/items?itemName=rust-lang.rust[previous official Rust plugin].
The latter is no longer maintained and should be uninstalled.

The server binary is stored in the extension install directory, which starts with `rust-lang.rust-analyzer-` and is located under:

* Linux: `~/.vscode/extensions`
* Linux (Remote, such as WSL): `~/.vscode-server/extensions`
* macOS: `~/.vscode/extensions`
* Windows: `%USERPROFILE%\.vscode\extensions`

As an exception, on NixOS, the extension makes a copy of the server and stores it under `~/.config/Code/User/globalStorage/rust-lang.rust-analyzer`.

Note that we only support the two most recent versions of VS Code.

==== Updates

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.

===== Nightly

We ship nightly releases for VS Code.
To help us out by testing the newest code, you can enable pre-release versions in the Code extension page.

==== Manual installation

Alternatively, download a VSIX corresponding to your platform from the
https://github.com/rust-lang/rust-analyzer/releases[releases] page.

Install the extension with the `Extensions: Install from VSIX` command within VS Code, or from the command line via:
[source]
----
$ code --install-extension /path/to/rust-analyzer.vsix
----

If you are running an unsupported platform, you can install `rust-analyzer-no-server.vsix` and compile or obtain a server binary.
Copy the server anywhere, then add the path to your settings.json, for example:
[source,json]
----
{ "rust-analyzer.server.path": "~/.local/bin/rust-analyzer-linux" }
----

==== Building From Source

Both the server and the Code plugin can be installed from source:

[source]
----
$ git clone https://github.com/rust-lang/rust-analyzer.git && cd rust-analyzer
$ cargo xtask install
----

You'll need Cargo, nodejs (matching a supported version of VS Code) and npm for this.

Note that installing via `xtask install` does not work for VS Code Remote, instead you'll need to install the `.vsix` manually.

If you're not using Code, you can compile and install only the LSP server:

[source]
----
$ cargo xtask install --server
----

Make sure that `.cargo/bin` is in `$PATH` and precedes paths where `rust-analyzer` may also be installed.
Specifically, `rustup` includes a proxy called `rust-analyzer`, which can cause problems if you're planning to use a source build or even a downloaded binary.

=== rust-analyzer Language Server Binary

Other editors generally require the `rust-analyzer` binary to be in `$PATH`.
You can download pre-built binaries from the https://github.com/rust-lang/rust-analyzer/releases[releases] page.
You will need to uncompress and rename the binary for your platform, e.g. from `rust-analyzer-aarch64-apple-darwin.gz` on Mac OS to `rust-analyzer`, make it executable, then move it into a directory in your `$PATH`.

On Linux to install the `rust-analyzer` binary into `~/.local/bin`, these commands should work:

[source,bash]
----
$ mkdir -p ~/.local/bin
$ curl -L https://github.com/rust-lang/rust-analyzer/releases/latest/download/rust-analyzer-x86_64-unknown-linux-gnu.gz | gunzip -c - > ~/.local/bin/rust-analyzer
$ chmod +x ~/.local/bin/rust-analyzer
----

Make sure that `~/.local/bin` is listed in the `$PATH` variable and use the appropriate URL if you're not on a `x86-64` system.

You don't have to use `~/.local/bin`, any other path like `~/.cargo/bin` or `/usr/local/bin` will work just as well.

Alternatively, you can install it from source using the command below.
You'll need the latest stable version of the Rust toolchain.

[source,bash]
----
$ git clone https://github.com/rust-lang/rust-analyzer.git && cd rust-analyzer
$ cargo xtask install --server
----

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-lang/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.

==== rustup

`rust-analyzer` is available in `rustup`:

[source,bash]
----
$ rustup component add rust-analyzer
----

==== Arch Linux

The `rust-analyzer` binary can be installed from the repos or AUR (Arch User Repository):

- https://www.archlinux.org/packages/extra/x86_64/rust-analyzer/[`rust-analyzer`] (built from latest tagged source)
- https://aur.archlinux.org/packages/rust-analyzer-git[`rust-analyzer-git`] (latest Git version)

Install it with pacman, for example:

[source,bash]
----
$ pacman -S rust-analyzer
----

==== Gentoo Linux

`rust-analyzer` is available in the GURU repository:

- https://gitweb.gentoo.org/repo/proj/guru.git/tree/dev-util/rust-analyzer?id=9895cea62602cfe599bd48e0fb02127411ca6e81[`dev-util/rust-analyzer`] builds from source
- https://gitweb.gentoo.org/repo/proj/guru.git/tree/dev-util/rust-analyzer-bin?id=9895cea62602cfe599bd48e0fb02127411ca6e81[`dev-util/rust-analyzer-bin`] installs an official binary release

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
$ emerge rust-analyzer-bin
----

==== macOS

The `rust-analyzer` binary can be installed via https://brew.sh/[Homebrew].

[source,bash]
----
$ brew install rust-analyzer
----

=== VS Code or VSCodium in Flatpak

Setting up `rust-analyzer` with a Flatpak version of Code is not trivial because of the Flatpak sandbox.
While the sandbox can be disabled for some directories, `/usr/bin` will always be mounted under `/run/host/usr/bin`.
This prevents access to the system's C compiler, a system-wide installation of Rust, or any other libraries you might want to link to.
Some compilers and libraries can be acquired as Flatpak SDKs, such as `org.freedesktop.Sdk.Extension.rust-stable` or `org.freedesktop.Sdk.Extension.llvm15`.

If you use a Flatpak SDK for Rust, there should be no extra steps necessary.

If you want to use Flatpak in combination with `rustup`, the following steps might help:

 - both Rust and `rustup` have to be installed using https://rustup.rs. Distro packages _will not_ work.
 - you need to launch Code, open a terminal and run `echo $PATH`
 - using https://flathub.org/apps/details/com.github.tchx84.Flatseal[Flatseal], you must add an environment variable called `PATH`.
   Set its value to the output from above, appending `:~/.cargo/bin`, where `~` is the path to your home directory.
   You must replace `~`, as it won't be expanded otherwise.
 - while Flatseal is open, you must enable access to "All user files"

A C compiler should already be available via `org.freedesktop.Sdk`.
Any other tools or libraries you will need to acquire  from Flatpak.

=== Emacs

Prerequisites: You have installed the <<rust-analyzer-language-server-binary,`rust-analyzer` binary>>.

To use `rust-analyzer`, you need to install and enable one of the two popular LSP client implementations for Emacs, https://github.com/joaotavora/eglot[Eglot] or https://github.com/emacs-lsp/lsp-mode[LSP Mode]. Both enable `rust-analyzer` by default in rust buffers if it is available.

==== Eglot

Eglot is the more minimalistic and lightweight LSP client for Emacs, integrates well with existing Emacs functionality and is built into Emacs starting from release 29.

After installing Eglot, e.g. via `M-x package-install` (not needed from Emacs 29), you can enable it via the `M-x eglot` command or load it automatically in `rust-mode` via

[source,emacs-lisp]
----
(add-hook 'rust-mode-hook 'eglot-ensure)
----

To enable clippy, you will need to configure the initialization options to pass the `check.command` setting.

[source,emacs-lisp]
----
(add-to-list 'eglot-server-programs
             '((rust-ts-mode rust-mode) .
               ("rust-analyzer" :initializationOptions (:check (:command "clippy")))))
----

For more detailed instructions and options see the https://joaotavora.github.io/eglot[Eglot manual] (also available from Emacs via `M-x info`) and the
https://github.com/joaotavora/eglot/blob/master/README.md[Eglot readme].

Eglot does not support the rust-analyzer extensions to the language-server protocol and does not aim to do so in the future. The https://github.com/nemethf/eglot-x#rust-analyzer-extensions[eglot-x] package adds experimental support for those LSP extensions.

==== LSP Mode

LSP-mode is the original LSP-client for emacs. Compared to Eglot it has a larger codebase and supports more features, like LSP protocol extensions.
With extension packages like https://github.com/emacs-lsp/lsp-mode[LSP UI] it offers a lot of visual eyecandy.
Further it integrates well with https://github.com/emacs-lsp/dap-mode[DAP mode] for support of the Debug Adapter Protocol.

You can install LSP-mode via `M-x package-install` and then run it via the `M-x lsp` command or load it automatically in rust buffers with

[source,emacs-lisp]
----
(add-hook 'rust-mode-hook 'lsp-deferred)
----

For more information on how to set up LSP mode and its extension package see the instructions in the https://emacs-lsp.github.io/lsp-mode/page/installation[LSP mode manual].
Also see the https://emacs-lsp.github.io/lsp-mode/page/lsp-rust-analyzer/[rust-analyzer section] for `rust-analyzer` specific options and commands, which you can optionally bind to keys.

Note the excellent https://robert.kra.hn/posts/2021-02-07_rust-with-emacs/[guide] from https://github.com/rksm[@rksm] on how to set-up Emacs for Rust development with LSP mode and several other packages.

=== Vim/Neovim

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.

There are several LSP client implementations for Vim or Neovim:

==== coc-rust-analyzer

1. Install coc.nvim by following the instructions at
   https://github.com/neoclide/coc.nvim[coc.nvim]
   (Node.js required)
2. Run `:CocInstall coc-rust-analyzer` to install
   https://github.com/fannheyward/coc-rust-analyzer[coc-rust-analyzer],
   this extension implements _most_ of the features supported in the VSCode extension:
   * automatically install and upgrade stable/nightly releases
   * same configurations as VSCode extension, `rust-analyzer.server.path`, `rust-analyzer.cargo.features` etc.
   * same commands too, `rust-analyzer.analyzerStatus`, `rust-analyzer.ssr` etc.
   * inlay hints for variables and method chaining, _Neovim Only_

Note: for code actions, use `coc-codeaction-cursor` and `coc-codeaction-selected`; `coc-codeaction` and `coc-codeaction-line` are unlikely to be useful.

==== LanguageClient-neovim

1. Install LanguageClient-neovim by following the instructions
   https://github.com/autozimu/LanguageClient-neovim[here]
   * The GitHub project wiki has extra tips on configuration

2. Configure by adding this to your Vim/Neovim config file (replacing the existing Rust-specific line if it exists):
+
[source,vim]
----
let g:LanguageClient_serverCommands = {
\ 'rust': ['rust-analyzer'],
\ }
----

==== YouCompleteMe

Install YouCompleteMe by following the instructions
  https://github.com/ycm-core/YouCompleteMe#installation[here].

rust-analyzer is the default in ycm, it should work out of the box.

==== ALE

To use the LSP server in https://github.com/dense-analysis/ale[ale]:

[source,vim]
----
let g:ale_linters = {'rust': ['analyzer']}
----

==== nvim-lsp

Neovim 0.5 has built-in language server support.
For a quick start configuration of rust-analyzer, use https://github.com/neovim/nvim-lspconfig#rust_analyzer[neovim/nvim-lspconfig].
Once `neovim/nvim-lspconfig` is installed, use `+lua require'lspconfig'.rust_analyzer.setup({})+` in your `init.vim`.

You can also pass LSP settings to the server:

[source,vim]
----
lua << EOF
local nvim_lsp = require'lspconfig'

local on_attach = function(client)
    require'completion'.on_attach(client)
end

nvim_lsp.rust_analyzer.setup({
    on_attach=on_attach,
    settings = {
        ["rust-analyzer"] = {
            imports = {
                granularity = {
                    group = "module",
                },
                prefix = "self",
            },
            cargo = {
                buildScripts = {
                    enable = true,
                },
            },
            procMacro = {
                enable = true
            },
        }
    }
})
EOF
----

See https://sharksforarms.dev/posts/neovim-rust/ for more tips on getting started.

Check out https://github.com/simrat39/rust-tools.nvim for a batteries included rust-analyzer setup for Neovim.

==== vim-lsp

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:

[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'],
        \   'initialization_options': {
        \     'cargo': {
        \       'buildScripts': {
        \         'enable': v:true,
        \       },
        \     },
        \     'procMacro': {
        \       'enable': v:true,
        \     },
        \   },
        \ })
endif
----

=== Sublime Text

==== Sublime Text 4:
* Follow the instructions in link:https://github.com/sublimelsp/LSP-rust-analyzer[LSP-rust-analyzer].

NOTE: Install link:https://packagecontrol.io/packages/LSP-file-watcher-chokidar[LSP-file-watcher-chokidar] to enable file watching (`workspace/didChangeWatchedFiles`).

==== Sublime Text 3:
* Install the <<rust-analyzer-language-server-binary,`rust-analyzer` binary>>.
* Install the link:https://packagecontrol.io/packages/LSP[LSP package].
* From the command palette, run `LSP: Enable Language Server Globally` and select `rust-analyzer`.

If it worked, you should see "rust-analyzer, Line X, Column Y" on the left side of the status bar, and after waiting a bit, functionalities 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.

=== GNOME Builder

GNOME Builder 3.37.1 and newer has native `rust-analyzer` support.
If the LSP binary is not available, GNOME Builder can install it when opening a Rust file.


=== Eclipse IDE

Support for Rust development in the Eclipse IDE is provided by link:https://github.com/eclipse/corrosion[Eclipse Corrosion].
If available in PATH or in some standard location, `rust-analyzer` is detected and powers editing of Rust files without further configuration.
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.
You'll need to close and reopen all .rs and Cargo files, or to restart the IDE, for this change to take effect.

=== Kate Text Editor

Support for the language server protocol is built into Kate through the LSP plugin, which is included by default.
It is preconfigured to use rust-analyzer for Rust sources since Kate 21.12.

To change rust-analyzer config options, start from the following example and put it into Kate's "User Server Settings" tab (located under the LSP Client settings):
[source,json]
----
{
    "servers": {
        "rust": {
            "initializationOptions": {
                "cachePriming": {
                    "enable": false
                },
                "check": {
                    "allTargets": false
                },
                "checkOnSave": false
            }
        }
    }
}
----
Then click on apply, and restart the LSP server for your rust project.

=== juCi++

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.

=== Kakoune

https://kakoune.org/[Kakoune] supports LSP with the help of https://github.com/kak-lsp/kak-lsp[`kak-lsp`].
Follow the https://github.com/kak-lsp/kak-lsp#installation[instructions] to install `kak-lsp`.
To configure `kak-lsp`, refer to the https://github.com/kak-lsp/kak-lsp#configuring-kak-lsp[configuration section] which is basically about copying the https://github.com/kak-lsp/kak-lsp/blob/master/kak-lsp.toml[configuration file] in the right place (latest versions should use `rust-analyzer` by default).

Finally, you need to configure Kakoune to talk to `kak-lsp` (see https://github.com/kak-lsp/kak-lsp#usage[Usage section]).
A basic configuration will only get you LSP but you can also activate inlay diagnostics and auto-formatting on save.
The following might help you get all of this.

[source,txt]
----
eval %sh{kak-lsp --kakoune -s $kak_session}  # Not needed if you load it with plug.kak.
hook global WinSetOption filetype=rust %{
    # Enable LSP
    lsp-enable-window

    # Auto-formatting on save
    hook window BufWritePre .* lsp-formatting-sync

    # Configure inlay hints (only on save)
    hook window -group rust-inlay-hints BufWritePost .* rust-analyzer-inlay-hints
    hook -once -always window WinSetOption filetype=.* %{
        remove-hooks window rust-inlay-hints
    }
}
----

=== Helix

https://docs.helix-editor.com/[Helix] supports LSP by default.
However, it won't install `rust-analyzer` automatically.
You can follow instructions for installing <<rust-analyzer-language-server-binary,`rust-analyzer` binary>>.

=== Visual Studio 2022

There are multiple rust-analyzer extensions for Visual Studio 2022 on Windows:

==== rust-analyzer.vs

(License: Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International)

https://marketplace.visualstudio.com/items?itemName=kitamstudios.RustAnalyzer[Visual Studio Marketplace]

https://github.com/kitamstudios/rust-analyzer/[GitHub]

Support for Rust development in the Visual Studio IDE is enabled by the link:https://marketplace.visualstudio.com/items?itemName=kitamstudios.RustAnalyzer[rust-analyzer] package. Either click on the download link or install from IDE's extension manager.
For now link:https://visualstudio.microsoft.com/downloads/[Visual Studio 2022] is required. All editions are supported viz. Community, Professional & Enterprise.
The package aims to provide 0-friction installation and therefore comes loaded with most things required including rust-analyzer binary. If anything it needs is missing, appropriate errors / warnings will guide the user. E.g. cargo.exe needs to be in path and the package will tell you as much.
This package is under rapid active development. So if you encounter any issues please file it at link:https://github.com/kitamstudios/rust-analyzer/[rust-analyzer.vs].

==== VS_RustAnalyzer

(License: GPL)

https://marketplace.visualstudio.com/items?itemName=cchharris.vsrustanalyzer[Visual Studio Marketplace]

https://github.com/cchharris/VS-RustAnalyzer[GitHub]

==== SourceGear Rust

(License: closed source)

https://marketplace.visualstudio.com/items?itemName=SourceGear.SourceGearRust[Visual Studio Marketplace]

https://github.com/sourcegear/rust-vs-extension[GitHub (docs, issues, discussions)]

* Free (no-cost)
* Supports all editions of Visual Studio 2022 on Windows: Community, Professional, or Enterprise

=== Lapce

https://lapce.dev/[Lapce] has a Rust plugin which you can install directly.
Unfortunately, it downloads an old version of `rust-analyzer`, but you can set the server path under Settings.

=== Crates

There is a package named `ra_ap_rust_analyzer` available on https://crates.io/crates/ra_ap_rust-analyzer[crates.io], for someone who wants to use it programmatically.

For more details, see https://github.com/rust-lang/rust-analyzer/blob/master/.github/workflows/publish.yml[the publish workflow].

=== Zed

https://zed.dev[Zed] has native `rust-analyzer` support.
If the LSP binary is not available, Zed can install it when opening a Rust file.

== Troubleshooting

Start with looking at the rust-analyzer version.
Try **rust-analyzer: Show RA Version** in VS Code (using **Command Palette** feature typically activated by Ctrl+Shift+P) or `rust-analyzer --version` in the command line.
If the date is more than a week ago, it's better to update rust-analyzer version.

The next thing to check would be panic messages in rust-analyzer's log.
Log messages are printed to stderr, in VS Code you can see them in the `Output > Rust Analyzer Language Server` tab of the panel.
To see more logs, set the `RA_LOG=info` environment variable, this can be done either by setting the environment variable manually or by using `rust-analyzer.server.extraEnv`, note that both of these approaches require the server to be restarted.

To fully capture LSP messages between the editor and the server, set `"rust-analyzer.trace.server": "verbose"` config and check
`Output > Rust Analyzer Language Server Trace`.

The root cause for many "`nothing works`" problems is that rust-analyzer fails to understand the project structure.
To debug that, first note the `rust-analyzer` section in the status bar.
If it has an error icon and red, that's the problem (hover will have somewhat helpful error message).
**rust-analyzer: Status** prints dependency information for the current file.
Finally, `RA_LOG=project_model=debug` enables verbose logs during project loading.

If rust-analyzer outright crashes, try running `rust-analyzer analysis-stats /path/to/project/directory/` on the command line.
This command type checks the whole project in batch mode bypassing LSP machinery.

When filing issues, it is useful (but not necessary) to try to minimize examples.
An ideal bug reproduction looks like this:

```bash
$ git clone https://github.com/username/repo.git && cd repo && git switch --detach commit-hash
$ rust-analyzer --version
rust-analyzer dd12184e4 2021-05-08 dev
$ rust-analyzer analysis-stats .
💀 💀 💀
```

It is especially useful when the `repo` doesn't use external crates or the standard library.

If you want to go as far as to modify the source code to debug the problem, be sure to take a look at the
https://github.com/rust-lang/rust-analyzer/tree/master/docs/dev[dev docs]!

== Configuration

**Source:** https://github.com/rust-lang/rust-analyzer/blob/master/crates/rust-analyzer/src/config.rs[config.rs]

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": {
    "buildScripts": {
      "enable": 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:

include::./generated_config.adoc[]

== Non-Cargo Based Projects

rust-analyzer does not require Cargo.
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 {
    /// Path to the sysroot directory.
    ///
    /// The sysroot is where rustc looks for the
    /// crates that are built-in to rust, such as
    /// std.
    ///
    /// https://doc.rust-lang.org/rustc/command-line-arguments.html#--sysroot-override-the-system-root
    ///
    /// To see the current value of sysroot, you
    /// can query rustc:
    ///
    /// ```
    /// $ rustc --print sysroot
    /// /Users/yourname/.rustup/toolchains/stable-x86_64-apple-darwin
    /// ```
    sysroot?: string;
    /// Path to the directory with *source code* of
    /// sysroot crates.
    ///
    /// By default, this is `lib/rustlib/src/rust/library`
    /// relative to the sysroot.
    ///
    /// It should point to the directory where std,
    /// core, and friends can be found:
    ///
    /// https://github.com/rust-lang/rust/tree/master/library.
    ///
    /// If provided, rust-analyzer automatically adds
    /// dependencies on sysroot crates. Conversely,
    /// if you omit this path, you can specify sysroot
    /// dependencies yourself and, for example, have
    /// several different "sysroots" in one graph of
    /// crates.
    sysroot_src?: 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 {
    /// Optional crate name used for display purposes,
    /// without affecting semantics. See the `deps`
    /// key for semantically-significant crate names.
    display_name?: string;
    /// Path to the root module of the crate.
    root_module: string;
    /// Edition of the crate.
    edition: "2015" | "2018" | "2021";
    /// Dependencies
    deps: Dep[];
    /// Should this crate be treated as a member of
    /// current "workspace".
    ///
    /// By default, inferred from the `root_module`
    /// (members are the crates which reside inside
    /// the directory opened in the editor).
    ///
    /// Set this to `false` for things like standard
    /// library and 3rd party crates to enable
    /// performance optimizations (rust-analyzer
    /// assumes that non-member crates don't change).
    is_workspace_member?: boolean;
    /// Optionally specify the (super)set of `.rs`
    /// files comprising this crate.
    ///
    /// By default, rust-analyzer assumes that only
    /// files under `root_module.parent` can belong
    /// to a crate. `include_dirs` are included
    /// recursively, unless a subdirectory is in
    /// `exclude_dirs`.
    ///
    /// Different crates can share the same `source`.
    ///
    /// If two crates share an `.rs` file in common,
    /// they *must* have the same `source`.
    /// rust-analyzer assumes that files from one
    /// source can't refer to files in another source.
    source?: {
        include_dirs: string[],
        exclude_dirs: string[],
    },
    /// The set of cfgs activated for a given crate, like
    /// `["unix", "feature=\"foo\"", "feature=\"bar\""]`.
    cfg: string[];
    /// Target triple for this Crate.
    ///
    /// Used when running `rustc --print cfg`
    /// to get target-specific cfgs.
    target?: string;
    /// Environment variables, used for
    /// the `env!` macro
    env: { [key: string]: string; },

    /// Whether the crate is a proc-macro crate.
    is_proc_macro: boolean;
    /// For proc-macro crates, path to compiled
    /// 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 three ways to feed `rust-project.json` to rust-analyzer:

* Place `rust-project.json` file at the root of the project, and rust-analyzer 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).
* Specify `"rust-analyzer.linkedProjects": [ { "roots": [...], "crates": [...] }]` inline.

Relative paths are interpreted relative to `rust-project.json` file location or (for inline JSON) relative to `rootUri`.

See https://github.com/rust-analyzer/rust-project.json-example for a small example.

You can set the `RA_LOG` environment variable to `rust_analyzer=info` to inspect how rust-analyzer handles config and project loading.

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 `rust-analyzer.check.overrideCommand` configuration.
As an example, the following configuration explicitly sets `cargo check` as the `check` command.

[source,json]
----
{ "rust-analyzer.check.overrideCommand": ["cargo", "check", "--message-format=json"] }
----

`check.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.

== Security

At the moment, rust-analyzer assumes that all code is trusted.
Here is a **non-exhaustive** list of ways to make rust-analyzer execute arbitrary code:

* proc macros and build scripts are executed by default
* `.cargo/config` can override `rustc` with an arbitrary executable
* `rust-toolchain.toml` 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.

== Privacy

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 does not access the network.

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.

For `rust-analyzer` developers, `cargo xtask release` uses the GitHub API to put together the release notes.

== Features

include::./generated_features.adoc[]

== Assists (Code Actions)

Assists, or code actions, are small local refactorings, available in a particular context.
They are usually triggered by a shortcut or by clicking a light bulb icon in the editor.
Cursor position or selection is signified by `┃` character.

include::./generated_assists.adoc[]

== Diagnostics

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.experimental.enable` or `rust-analyzer.diagnostics.disabled` settings.

=== Clippy

To run `cargo clippy` instead of `cargo check`, you can set `"rust-analyzer.check.command": "clippy"`.

include::./generated_diagnostic.adoc[]

== Editor Features
=== VS Code

==== Color configurations

It is possible to change the foreground/background color and font family/size of inlay hints.
Just add this to your `settings.json`:

[source,jsonc]
----
{
  "editor.inlayHints.fontFamily": "Courier New",
  "editor.inlayHints.fontSize": 11,

  "workbench.colorCustomizations": {
    // Name of the theme you are currently using
    "[Default Dark+]": {
      "editorInlayHint.foreground": "#868686f0",
      "editorInlayHint.background": "#3d3d3d48",

      // Overrides for specific kinds of inlay hints
      "editorInlayHint.typeForeground": "#fdb6fdf0",
      "editorInlayHint.parameterForeground": "#fdb6fdf0",
    }
  }
}
----

==== Semantic style customizations

You can customize the look of different semantic elements in the source code.
For example, mutable bindings are underlined by default and you can override this behavior by adding the following section to your `settings.json`:

[source,jsonc]
----
{
  "editor.semanticTokenColorCustomizations": {
    "rules": {
      "*.mutable": {
        "fontStyle": "", // underline is the default
      },
    }
  },
}
----

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`:

[source,jsonc]
----
{
   "editor.semanticTokenColorCustomizations": {
         "rules": {
             "operator.unsafe": "#ff6600",
             "function.unsafe": "#ff6600",
             "method.unsafe": "#ff6600"
         }
    },
}
----

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:

[source,jsonc]
----
{
   "editor.semanticTokenColorCustomizations": {
         "rules": {
             "operator.unsafe": "#ff6600"
         },
         "[Ayu Light]": {
            "rules": {
               "operator.unsafe": "#572300"
            }
         }
    },
}
----

Make sure you include the brackets around the theme name. For example, use `"[Ayu Light]"` to customize the theme Ayu Light.

==== Special `when` clause context for keybindings.
You may use `inRustProject` context to configure keybindings for rust projects only.
For example:

[source,json]
----
{
  "key": "ctrl+alt+d",
  "command": "rust-analyzer.openDocs",
  "when": "inRustProject"
}
----
More about `when` clause contexts https://code.visualstudio.com/docs/getstarted/keybindings#_when-clause-contexts[here].

==== Setting runnable environment variables
You can use "rust-analyzer.runnables.extraEnv" setting to define runnable environment-specific substitution variables.
The simplest way for all runnables in a bunch:
```jsonc
"rust-analyzer.runnables.extraEnv": {
    "RUN_SLOW_TESTS": "1"
}
```

Or it is possible to specify vars more granularly:
```jsonc
"rust-analyzer.runnables.extraEnv": [
    {
        // "mask": null, // null mask means that this rule will be applied for all runnables
        "env": {
             "APP_ID": "1",
             "APP_DATA": "asdf"
        }
    },
    {
        "mask": "test_name",
        "env": {
             "APP_ID": "2", // overwrites only APP_ID
        }
    }
]
```

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.

If needed, you can set different values for different platforms:
```jsonc
"rust-analyzer.runnables.extraEnv": [
    {
        "platform": "win32", // windows only
        "env": {
             "APP_DATA": "windows specific data"
        }
    },
    {
        "platform": ["linux"],
        "env": {
             "APP_DATA": "linux data",
        }
    },
    { // for all platforms
        "env": {
             "APP_COMMON_DATA": "xxx",
        }
    }
]
```

==== Compiler feedback from external commands

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": 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`:

```json
{
    "label": "Watch",
    "group": "build",
    "type": "shell",
    "command": "cargo watch",
    "problemMatcher": "$rustc-watch",
    "isBackground": true
}
```

==== Live Share

VS Code Live Share has partial support for rust-analyzer.

Live Share _requires_ the official Microsoft build of VS Code, OSS builds will not work correctly.

The host's rust-analyzer instance will be shared with all guests joining the session.
The guests do not have to have the rust-analyzer extension installed for this to work.

If you are joining a Live Share session and _do_ have rust-analyzer installed locally, commands from the command palette will not work correctly since they will attempt to communicate with the local server.