RA Assist

A VS Code extension for toggling rust-analyzer between Host (x86_64) and MU (RISC-V accelerator) targets.

Features

Toggle rust-analyzer target via status bar button, keyboard shortcut, or command palette
Automatic RUSTFLAGS configuration (--cfg=host / --cfg=mu)
cargo.cfgs with ! prefix to gray out inactive cfg blocks in the editor
Configurable directory exclusions per mode
Status bar indicator showing current mode
Auto-fallback to Host mode if MU target file is missing
QEMU CodeLens: QEMU <ver> Debug / QEMU <ver> Release buttons above fn main() and #[test] functions
Automatic TOML formatter setup — configures even-better-toml with system taplo when taplo.toml exists

Installation

VS Code Marketplace

Search for "RA Assist" in the Extensions view (Ctrl+Shift+X), or run:

ext install eshonar.ra-assist

Install from VSIX

Download the .vsix file from GitHub Releases, then:

code --install-extension ra-assist-*.vsix

Usage

Toggle Target

Method	Action
Status bar	Click on `Host` or `MU` indicator
Keyboard	`Ctrl+Alt+T` (Windows/Linux) or `Cmd+Alt+T` (Mac)
Command palette	`Ctrl+Shift+P` then `RA Assist: Toggle Target`

Mode Behavior

Mode	RUSTFLAGS	rust-analyzer target
Host	`--cfg=host`	Default (native)
MU	`--cfg=mu`	Custom RISC-V target JSON

QEMU CodeLens

The extension adds a pair of CodeLens buttons above fn main() and #[test] functions — QEMU <ver> Debug and QEMU <ver> Release, where <ver> is the CXL version selected in the status bar hover. Clicking one runs the binary/test through QEMU via the configured runner script; Debug uses cargo's dev profile and Release adds --release.

fn main() → cargo run [--release] --package <name> with QEMU runner
#[test] → cargo test [--release] --package <name> -- <test> --exact --nocapture --include-ignored with QEMU runner

--include-ignored is always passed: the lens names one exact test, so without it a #[ignore] test would be filtered out instead of run.

The runner is set via a configurable environment variable (default: CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_RUNNER), overriding .cargo/config.toml.

Debug and release builds land in separate target/ subdirectories, so alternating between the buttons does not invalidate the other's artifacts. Do not click both at once, though — the QEMU emulator is a single instance.

Configuration

Add to your .vscode/settings.json:

{
  "ra-assist.targetTriplePath": "xcena",
  "ra-assist.targetTriple": "riscv64imfdxmetis-unknown-none-elf.json",
  "ra-assist.muExcludeDirs": ["mu-builder"],
  "ra-assist.hostExcludeDirs": []
}

Settings

Setting	Type	Default	Description
`targetTriplePath`	string	`"xcena"`	Directory containing the target JSON (relative to workspace or absolute)
`targetTriple`	string	`"riscv64imfdxmetis-unknown-none-elf.json"`	Target triple JSON filename
`excludeDirs`	array	`[]`	Directories to exclude from rust-analyzer in all modes
`muExcludeDirs`	array	`["mu-builder"]`	Directories to exclude in MU mode
`hostExcludeDirs`	array	`[]`	Directories to exclude in Host mode
`qemuCodeLensEnabled`	boolean	`true`	Enable the QEMU Debug/Release CodeLens pair above `fn main()` and `#[test]`
`qemuRunner`	string	`"./dev/run.sh --qemu"`	Runner command for QEMU execution
`qemuRunnerEnvVar`	string	`"CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_RUNNER"`	Environment variable for the cargo runner
`qemuRunnerSearchPaths`	array	`["dev/run.sh", "mjol/dev/run.sh"]`	Paths to search for the runner script (walked upward)
`qemuTestArgs`	array	`[]`	Extra cargo-level arguments before `--` (e.g. `["--features", "foo"]`). Profile flags (`--release`, `--profile`) are ignored — the Debug/Release buttons own the profile
`qemuTestEnv`	object	`{}`	Extra environment variables for QEMU execution

How It Works

When toggling modes, the extension:

Updates rust-analyzer.cargo.extraEnv.RUSTFLAGS with the appropriate --cfg flag
Updates rust-analyzer.runnables.extraEnv.RUSTFLAGS for Run/Debug buttons
Sets rust-analyzer.cargo.cfgs with ! prefix to gray out inactive cfg blocks (e.g., ["mu", "!host"])
Sets/removes rust-analyzer.cargo.target to the MU target JSON path
Configures rust-analyzer.cargo.extraArgs for build-std (MU mode only)
Updates rust-analyzer.files.excludeDirs based on mode-specific exclusion lists
Restarts rust-analyzer to apply changes
If taplo.toml exists, configures TOML formatter (even-better-toml) to use system taplo binary

Requirements

VS Code 1.75.0 or higher
rust-analyzer extension
For MU mode: valid target triple JSON file in the configured path

License

Apache-2.0