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

// Master copy of this document lives in the https://github.com/rust-analyzer/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.

To improve this document, send a pull request against
https://github.com/rust-analyzer/rust-analyzer/blob/master/docs/user/manual.adoc[this file].

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
```

=== VS Code

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

You can install the latest release of the plugin from
https://marketplace.visualstudio.com/items?itemName=matklad.rust-analyzer[the marketplace].
By default, the plugin will prompt you to download the matching version of the server as well:

image::https://user-images.githubusercontent.com/9021944/75067008-17502500-54ba-11ea-835a-f92aac50e866.png[]

[NOTE]
====
To disable this notification put the following to `settings.json`

[source,json]
----
{ "rust-analyzer.updates.askBeforeDownload": false }
----
====

The server binary is stored in:

* Linux: `~/.config/Code/User/globalStorage/matklad.rust-analyzer`
* macOS: `~/Library/Application\ Support/Code/User/globalStorage/matklad.rust-analyzer`
* Windows: `%APPDATA%\Code\User\globalStorage\matklad.rust-analyzer`

Note that we only support 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 with testing the newest code and follow the bleeding edge of our `master`, please use the following config:

[source,json]
----
{ "rust-analyzer.updates.channel": "nightly" }
----

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.

If you don't want to be asked for `Download now` every day when the new nightly version is released add the following to your `settings.json`:
[source,json]
----
{ "rust-analyzer.updates.askBeforeDownload": false }
----

NOTE: Nightly extension should **only** be installed via the `Download now` action from VS Code.

==== Building From Source

Alternatively, both the server and the plugin can be installed from source:

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

You'll need Cargo, nodejs 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.

==== Troubleshooting

Here are some useful self-diagnostic commands:

* **Rust Analyzer: Show RA Version** shows the version of `rust-analyzer` binary
* **Rust Analyzer: Status** prints some statistics about the server, like the few latest LSP requests
* To enable server-side logging, run with `env RA_LOG=info` and see `Output > Rust Analyzer Language Server` in VS Code's panel.
* To log all LSP requests, add `"rust-analyzer.trace.server": "verbose"` to the settings and look for `Server Trace` in the panel.
* To enable client-side logging, add `"rust-analyzer.trace.extension": true` to the settings and open the `Console` tab of VS Code developer tools.

=== rust-analyzer Language Server Binary

Other editors generally require the `rust-analyzer` binary to be in `$PATH`.
You can download the pre-built binary from the https://github.com/rust-analyzer/rust-analyzer/releases[releases] page.
Typically, you then need to rename the binary for your platform, e.g. `rust-analyzer-mac` if you're on Mac OS, to `rust-analyzer` and make it executable in addition to moving it into a directory in your `$PATH`.

On Linux to install the `rust-analyzer` binary into `~/.local/bin`, this commands could be used

[source,bash]
----
$ curl -L https://github.com/rust-analyzer/rust-analyzer/releases/latest/download/rust-analyzer-linux -o ~/.local/bin/rust-analyzer
$ chmod +x ~/.local/bin/rust-analyzer
----

Ensure `~/.local/bin` is listed in the `$PATH` variable.

Alternatively, you can install it from source using the following command:

[source,bash]
----
$ git clone https://github.com/rust-analyzer/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-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.

==== Arch Linux

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

- https://www.archlinux.org/packages/community/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
----

=== Emacs

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

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].
2. Set `lsp-rust-server` to `'rust-analyzer`.
3. Run `lsp` in a Rust buffer.
4. (Optionally) bind commands like `lsp-rust-analyzer-join-lines`, `lsp-extend-selection` and `lsp-rust-analyzer-expand-macro` to keys.

=== 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.

The 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.serverPath`, `rust-analyzer.cargo.features` etc.
   * same commands too, `rust-analyzer.analyzerStatus`, `rust-analyzer.ssr` etc.
   * inlay hints for method chaining support, _Neovim Only_
   * semantic highlighting is not implemented yet

==== 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

1. Install YouCompleteMe by following the instructions
  https://github.com/ycm-core/lsp-examples#rust-rust-analyzer[here]

2. Configure by adding this to your vim/neovim config file (replacing the existing Rust-specific line if it exists):
+
[source,vim]
----
let g:ycm_language_server =
\ [
\   {
\     'name': 'rust',
\     'cmdline': ['rust-analyzer'],
\     'filetypes': ['rust'],
\     'project_root_files': ['Cargo.toml']
\   }
\ ]
----

==== 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 (not yet released) has built-in language server support.
For a quick start configuration of rust-analyzer, use https://github.com/neovim/nvim-lsp#rust_analyzer[neovim/nvim-lsp].
Once `neovim/nvim-lsp` is installed, use `+lua require'nvim_lsp'.rust_analyzer.setup({})+` in your `init.vim`.

=== Sublime Text 3

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

You also need the `LSP` package. To install it:

1. If you've never installed a Sublime Text package, install Package Control:
   * Open the command palette (Win/Linux: `ctrl+shift+p`, Mac: `cmd+shift+p`)
   * Type `Install Package Control`, press enter
2. In the command palette, run `Package control: Install package`, and in the list that pops up, type `LSP` and press enter.

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.

=== GNOME Builder

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`).
2. Enable the Rust Builder plugin.

==== GNOME Builder (Nightly)

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.

== 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 {
   /// 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).
* 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.

== 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[]

== Editor Features
=== VS Code
==== Special `when` clause context for keybindings.
You may use `inRustProject` context to configure keybindings for rust projects only. For example:
[source,json]
----
{
  "key": "ctrl+i",
  "command": "rust-analyzer.toggleInlayHints",
  "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.runnableEnv" setting to define runnable environment-specific substitution variables.
The simplest way for all runnables in a bunch:
```jsonc
"rust-analyzer.runnableEnv": {
    "RUN_SLOW_TESTS": "1"
}
```

Or it is possible to specify vars more granularly:
```jsonc
"rust-analyzer.runnableEnv": [
    {
        // "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 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.

==== 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.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`:

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