docs/rust_analyzer.vm

#[[
## Overview

For [non-Cargo projects](https://rust-analyzer.github.io/manual.html#non-cargo-based-projects),
[rust-analyzer](https://rust-analyzer.github.io/) depends on a `rust-project.json` file at the
root of the project that describes its structure. The `rust_analyzer` rule facilitates generating
such a file.

### Setup

First, add the following to the `WORKSPACE` file:

```python
load("@rules_rust//tools/rust_analyzer:deps.bzl", "rust_analyzer_deps")

rust_analyzer_deps()
```

Next, add the following lines to the `.bazelrc` file of your workspace:
```
build --repo_env=RULES_RUST_TOOLCHAIN_INCLUDE_RUSTC_SRCS=true
```

This will ensure rust source code is available to `rust-analyzer`. Users
can also set `include_rustc_srcs = True` on any `rust_repository` or
`rust_repositories` calls in the workspace but the environment variable
has higher priority and can override the attribute.

Finally, run `bazel run @rules_rust//tools/rust_analyzer:gen_rust_project`
whenever dependencies change to regenerate the `rust-project.json` file. It
should be added to `.gitignore` because it is effectively a build artifact.
Once the `rust-project.json` has been generated in the project root,
rust-analyzer can pick it up upon restart.

#### VSCode

To set this up using [VSCode](https://code.visualstudio.com/), users should first install the
[rust_analyzer plugin](https://marketplace.visualstudio.com/items?itemName=matklad.rust-analyzer).
With that in place, the following task can be added to the `.vscode/tasks.json` file of the workspace
to ensure a `rust-project.json` file is created and up to date when the editor is opened.

```json
{
    "version": "2.0.0",
    "tasks": [
        {
            "label": "Generate rust-project.json",
            "command": "bazel",
            "args": ["run", "@rules_rust//tools/rust_analyzer:gen_rust_project"],
            "options": {
                "cwd": "${workspaceFolder}"
            },
            "group": "build",
            "problemMatcher": [],
            "presentation": {
                "reveal": "never",
                "panel": "dedicated",
            },
            "runOptions": {
                "runOn": "folderOpen"
            }
        },
    ]
}
```
]]#