rust-analyzer/docs/user/manual.adoc

= 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.

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

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 `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.

=== 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
}
```